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Title: The Manufacture of Paper

Author: R. W. Sindall

Release date: July 30, 2014 [eBook #46449]

Language: English

Credits: Produced by Chris Curnow, Peter Becker and the Online
        Distributed Proofreading Team at http://www.pgdp.net (This
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  | Transcriber's Notes                                                |
  |                                                                    |
  | Passages in italics are indicated by _italics_. Passages in bold   |
  | are indicated by $bold$. Passages in small caps are shown in       |
  | title case without explicit indication. Subscripted characters     |
  | are indicated by _{subscript}. Superscripted characters are        |
  | indicated by ^x (x is a single character). [OE] is the latin OE    |
  | ligature.                                                          |
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  | A list of inconsistencies and corrections is at the end of the     |
  | text.                                                              |
  +--------------------------------------------------------------------+




                            THE MANUFACTURE
                               OF PAPER

                                  BY

                         R. W. SINDALL, F.C.S.

     CONSULTING CHEMIST TO THE WOOD PULP AND PAPER TRADES; LECTURER
       ON PAPER-MAKING FOR THE HERTFORDSHIRE COUNTY COUNCIL, THE
          BUCKS COUNTY COUNCIL, THE PRINTING AND STATIONERY
            TRADES AT EXETER HALL, 1903-4, THE INSTITUTE
               OF PRINTERS; TECHNICAL ADVISER TO THE
                     GOVERNMENT OF INDIA, 1905

      AUTHOR OF "PAPER TECHNOLOGY," "THE SAMPLING OF WOOD PULP"
       JOINT AUTHOR OF "THE C.B.S. UNITS, OR STANDARDS OF PAPER
            TESTING," "THE APPLICATIONS OF WOOD PULP," ETC.

            WITH ILLUSTRATIONS, AND A BIBLIOGRAPHY OF WORKS
                RELATING TO CELLULOSE AND PAPER-MAKING

                           [Illustration]

                             NEW YORK
                     D. VAN NOSTRAND COMPANY
                 23 MURRAY AND 27 WARREN STREETS

                               1908




PREFACE


Paper-making, in common with many other industries, is one in which
both engineering and chemistry play important parts. Unfortunately
the functions of the engineer and chemist are generally regarded as
independent of one another, so that the chemist is only called in by
the engineer when efforts along the lines of mechanical improvement
have failed, and _vice versa_. It is impossible, however, to draw a
hard and fast line, and the best results in the art of paper-making are
only possible when the manufacturer appreciates the fact that the skill
of both is essential to progress and commercial success.

In the present elementary text-book it is only proposed to give an
outline of the various stages of manufacture and to indicate some of
the improvements made during recent years.

The author begs to acknowledge his indebtedness to manufacturers and
others who have given permission for the use of illustrations.




CONTENTS


                                                                  PAGE

    PREFACE                                                          v

    LIST OF ILLUSTRATIONS                                           ix


  CHAPTER

     I.  HISTORICAL NOTICE                                           1

    II.  CELLULOSE AND PAPER-MAKING FIBRES                          20

   III.  THE MANUFACTURE OF PAPER FROM RAGS                         47

    IV.  ESPARTO AND STRAW                                          72

     V.  WOOD PULP, AND WOOD PULP PAPERS                            95

    VI.  BROWN PAPERS AND BOARDS                                   126

   VII.  SPECIAL KINDS OF PAPER                                    137

  VIII.  CHEMICALS USED IN PAPER-MAKING                            153

    IX.  THE PROCESS OF "BEATING"                                  175

     X.  THE DYEING AND COLOURING OF PAPER PULP                    199

    XI.  PAPER MILL MACHINERY                                      214

   XII.  THE DETERIORATION OF PAPER                                229

  XIII.  BIBLIOGRAPHY                                              253


    INDEX                                                          273




LIST OF ILLUSTRATIONS


  FIG.                                                            PAGE

  1. SHEET OF PAPYRUS, SHOWING THE LAYERS CROSSING ONE
       ANOTHER                                                       3

  2. AN EARLY PAPER MILL (FROM "KULTURHISTORISCHEN BILDERBUCH,"
       A.D. 1564)                                                   10

  3. THE PAPER MILL OF ULMAN STROMER, A.D. 1390 (SUPPOSED
       TO BE THE OLDEST KNOWN DRAWING OF A PAPER MILL)              12

  4. THE FIRST PAPER MACHINE, A.D. 1802. PLAN AND ELEVATION         17

  5. THE IMPROVED PAPER MACHINE OF A.D. 1810                        18

  6. A RAG SORTING HOUSE                                            47

  7. A RAG DUSTER                                                   49

  8. A RAG CUTTER                                                   50

  9. INTERIOR OF PAPER MILL FOR HAND-MADE PAPER (R. BATCHELOR
       & SONS)                                                      51

  10. VIEW OF A RAG BOILER, SHOWING CONNECTIONS                     52

  11. A BREAKING AND WASHING ENGINE                                 54

  12. OETTEL AND HAAS' APPARATUS FOR THE MANUFACTURE OF
        ELECTROLYTIC BLEACH LIQUOR                                  58

  13. THE "HOLLANDER" BEATING ENGINE                                59

  14. THE HAND MOULD, SHOWING FRAME AND DECKLE                      61

  15. APPARATUS FOR SIZING PAPER IN CONTINUOUS ROLLS                63

  16. A SUPERCALENDER                                               65

  17. THE FIRST WATERMARK IN PAPER                                  67

  18. COTTON                                                        69

  19. LINEN                                                         70

  20. AN ESPARTO DUSTER                                             74

  21. SINCLAIR'S "VOMITING" ESPARTO BOILER                          75

  22. A PORION EVAPORATOR                                           76

  23. SCOTT'S MULTIPLE EFFECT EVAPORATOR                            79

  24. A PRESSE-PÂTE FOR ESPARTO PULP                                85

  25. ESPARTO PULP                                                  88

  26. A CYLINDRICAL DIGESTER FOR BOILING FIBRE                      89

  27. STRAW                                                         93

  28. A PAIR OF BARKERS FOR REMOVING BARK FROM LOGS OF WOOD         98

  29. VIEW OF HORIZONTAL GRINDER (A), WITH SECTION (B)              99

  30. A VERTICAL GRINDER FOR MAKING HOT GROUND MECHANICAL
        WOOD PULP                                                  101

  31. CENTRIFUGAL SCREEN FOR WOOD PULP                             102

  32. SECTION OF CENTRIFUGAL SCREEN FOR WOOD PULP                  103

  33. WOOD PULP DIGESTER, PARTLY IN ELEVATION, PARTLY IN
        SECTION                                                    106

  34. VIEW OF ORDINARY SULPHUR-BURNING OVENS                       108

  35. SPRUCE WOOD PULP                                             114

  36. MECHANICAL WOOD PULP                                         115

  37. THE SCREENS FOR REMOVING COARSE FIBRES FROM BEATEN
        PULP                                                       118

  38. THE PAPER MACHINE (WET END SHOWING WIRE)                     119

  39. PAPER MACHINE SHOWING WIRE, PRESS ROLLS, AND DRYING
        CYLINDERS                                                  123

  40. SINGLE CYLINDER OR YANKEE MACHINE                            130

  41. SECTION OF WET PRESS, OR BOARD MACHINE                       131

  42. DOUBLE CYLINDER BOARD MACHINE                                133

  43. APPARATUS FOR MAKING PARCHMENT PAPER                         138

  44. GENERAL ARRANGEMENT OF PLANT FOR MAKING "ART" PAPER          143

  45. SECTIONAL ELEVATION OF "COATING" PLANT                       144

  46. COTTON PULP BEATEN 8 HOURS                                   179

  47. COTTON PULP BEATEN 37 HOURS                                  180

  48. PLAN AND SECTIONAL ELEVATION OF A "HOLLANDER"                185

  49. BEATING ENGINE WITH FOUR BEATER ROLLS                        186

  50. UMPHERSTON BEATER                                            188

  51. SECTION OF UMPHERSTON BEATING ENGINE                         189

  52. NUGENT'S BEATING ENGINE WITH PADDLES FOR CIRCULATING
        THE PULP                                                   190

  53. A "TOWER" BEATING ENGINE WITH CENTRIFUGAL PUMP FOR
        CIRCULATING PULP                                           191

  54. WORKING PARTS OF A MODERN REFINING ENGINE                    192

  55. CONVENTIONAL DIAGRAM OF A WATER SOFTENING PLANT              216

  56. AN "ENCLOSED" STEAM ENGINE                                   220

  57. AN ELECTRICALLY DRIVEN PAPER MACHINE                         222

  58. DIAGRAM OF THE "EIBEL" PROCESS                               223




THE MANUFACTURE OF PAPER




CHAPTER I

HISTORICAL NOTICE


_History._--The art of paper-making is undoubtedly one of the most
important industries of the present day. The study of its development
from the early bygone ages when men were compelled to find some means
for recording important events and transactions is both interesting and
instructive, so that a short summary of the known facts relating to the
history of paper may well serve as an introduction to an account of the
manufacture and use of this indispensable article.

_Tradition._--The early races of mankind contented themselves with
keeping alive the memory of great achievements by means of tradition.
Valiant deeds were further commemorated by the planting of trees, the
setting up of heaps of stones, and the erection of clumsy monuments.

_Stone Obelisks._--The possibility of obtaining greater accuracy by
carving the rude hieroglyphics of men and animals, birds and plants,
soon suggested itself as an obvious improvement; and as early as B.C.
4000 the first records which conveyed any meaning to later ages were
faithfully inscribed, and for the most part consigned to the care of
the priests.

_Clay Tablets._--The ordinary transactions of daily life, the writings
of literary and scientific men, and all that was worthy of note in
the history of such nations as Chaldea and Assyria have come down to
us also, inscribed on clay tablets, which were rendered durable by
careful baking. On a tablet of clay, one of the earliest specimens of
writing in existence, now preserved in the British Museum, is recorded
a proposal of marriage, written about B.C. 1530, from one of the
Pharaohs, asking for the hand of the daughter of a Babylonian king.

_Waxed Boards._--Bone, ivory, plates of metal, lead, gold, and brass,
were freely used, and at an early period wooden boards covered with
wax were devised by the Romans. In fact, any material having a soft
impressionable surface was speedily adopted as a medium for the
permanent expression of men's fancy, so that it is not strange to find
instances of documents written on such curious substances as animal
skins, hides, dried intestines, and leather. The works of Homer,
preserved in one of the Egyptian libraries in the days of Ptolemæus
Philadelphus, were said to have been written in letters of gold on the
skins of serpents.

_Leaves, Bark._--The first actual advance in the direction of paper,
as commonly understood, was made when the leaves and bark of trees
were utilised. The latter especially came speedily into favour, and
the extensive use of the inner bark (_liber_) made rapid headway.
Manuscripts and documents written on this liber are to be found in many
museums.

_Papyrus._--The discovery of the wonderful properties of the Egyptian
papyrus was a great step in developing the art of paper-making. The
date of this discovery is very uncertain, but one of the earliest
references is to be found in the works of Pliny, where mention is made
of the writings of Numa, who lived about B.C. 670. This celebrated
plant had long been noted for its value in the manufacture of mats,
cordage, and wearing apparel, but its fame rests upon its utility in
quite a different direction, namely, for conveying to posterity the
written records of those early days which have proved a source of
unending interest to antiquaries.

[Illustration: FIG. 1.--Sheet of Papyrus, showing the layers crossing
one another (Evans).]

The Egyptian papyrus was made from the fine layers of fibrous matter
surrounding the parent stem. These layers were removed by means of a
sharp tool, spread out on a board, moistened with some gummy water, and
then covered with similar layers placed over them crosswise. The sheets
so produced were pressed, dried, and polished with a piece of ivory or
a smooth stone. Long rolls of papyrus were formed by pasting several
sheets together to give what was termed a _volumen_.

_Roman Papyri._--The Romans improved the process of manufacture,
and were able to produce a variety of papers, to which they gave
different names, such as _Charta hieratica_ (holy paper, used by
priests), _Charta Fanniana_ (a superior paper made by Fannius), _Charta
emporetica_ (shop or wrapping paper), _Charta Saitica_ (after the city
of Sais), etc. The papyrus must have been used in great quantities
for this purpose, since recent explorations in Eastern countries have
brought to light enormous finds of papyri in a wonderful state of
preservation. In 1753, when the ruins of Herculaneum were unearthed, no
less than 1,800 rolls were discovered. During the last ten years huge
quantities have been brought to England.

_Parchment._--Parchment succeeded papyrus as an excellent writing
material, being devised as a substitute for the latter by the
inhabitants of Pergamus on account of the prohibited exportation of
Egyptian papyrus. For many centuries parchment held a foremost place
amongst the available materials serving the purpose of paper, and even
to-day it is used for important legal documents. This parchment was
made from the skins of sheep and goats, which were first steeped in
lime pits, and then scraped. By the plentiful use of chalk and pumice
stone the colour and surface of the parchment were greatly enhanced.
Vellum, prepared in a similar manner from the skins of calves, was
also extensively employed as a writing material, and was probably the
first material used for binding books. Until comparatively recent times
the term "parchment" comprehended vellum, but the latter substance is
much superior to that manufactured from sheep and goat skins.

_Paper._--The Chinese are now generally credited with the art of making
paper of the kind most familiar to us, that is from fibrous material
first reduced to the condition of pulp. Materials such as strips of
bark, leaves, and papyrus cannot of course be included in a definition
like this, which one writer has condensed into the phrase "Paper is an
aqueous deposit of vegetable fibre."

A.D. 105.--The earliest reference to the manufacture of paper is to be
found in the Chinese Encyclopædia, wherein it is stated that Ts'ai-Lun,
a native of Kuei-yang, entered the service of the Emperor Ho-Ti in A.D.
75, and devoting his leisure hours to study, suggested the use of silk
and ink as a substitute for the bamboo tablet and stylus. Subsequently
he succeeded in making paper from bark, tow, old linen, and fish nets
(A.D. 105). He was created marquis in A.D. 114 for his long years of
service and his ability.

A.D. 704.--It has been commonly asserted that raw cotton, or cotton
wool, was first used by the Arabs at this date for the manufacture
of paper, they having learnt the art from certain Chinese prisoners
captured at the occupation of Samarkand by the Arabs. The complete
conquest of Samarkand does not, however, seem to have taken place until
A.D. 751, and there is little doubt that this date should be accepted
for the introduction of the art of paper-making among the Arabs.

_Recent Researches._--Professors Wiesner and Karabacek have ascertained
one or two most important and interesting facts concerning the actual
manufacture of _pure_ rag paper. In 1877 a great quantity of ancient
manuscripts was found at El-Faijum, in Egypt, comprising about 100,000
documents in ten languages, extending from B.C. 1400 to A.D.
1300, many of which were written on paper. The documents were closely
examined in 1894 by these experts, at the request of the owner, the
Archduke Rainer of Austria.

Researches of a later date resulted in the discovery of some further
interesting documents which appear to establish with some degree of
certainty the approximate date at which _pure_ rag paper, that is,
paper made entirely from rag, was manufactured.

Chinese documents dated A.D. 768-786, which have been reported upon
by Dr. Hoernle, and others dated A.D. 781-782-787, reported upon by
Dr. Stein as recently as 1901, appear to show what materials were used
by the Chinese paper-makers in Western Turkestan. The manuscripts
mentioned were dug out from the sand-buried site of Dandan Uilig, in
Eastern Turkestan.

Professor Wiesner found that all the papers of the Rainer collection
were made of _linen_ rag, with an occasional trace of _cotton_,
probably added accidentally. The earliest dated paper was a letter A.D.
874, but two documents, which from other reasons could be identified as
belonging to A.D. 792, proved that at the end of the eighth century the
Arabs understood the art of making linen paper on network moulds, and
further that they added starch for the purpose of sizing and loading
the paper.

Professor Karabacek advances some ingenious explanations as to the
origin of the idea that raw cotton was first used for paper-making,
and he suggests that the legend owes its origin to a misunderstanding
of terms. In mediæval times paper was known as _Charta bombycina_, and
sometimes as _Charta Damascena_, the latter from its place of origin.

Paper was also made in Bambyce, and a natural confusion arose between
the terms, since the word _bombyx_ was used as a name for cotton, and
the paper commonly in use suggested that material to the mind of the
observer, and the name became corrupted to _bombycina_.

The suggestions of Professor Karabacek, together with the microscopical
investigations of Dr. Wiesner, appear to show that paper made entirely
from raw cotton fibre was not known.

_Invention of Rag Paper._--Dr. Hoernle, in discussing this question,
points out that, taking A.D. 751 as the date when the Arabs learnt
the art of paper-making, and A.D. 792 as the date when paper made
entirely of linen rag was produced, the date of the invention of rag
paper must lie between these two dates. The documents discovered in
Eastern Turkestan and bearing the dates mentioned, which papers fill
up the gap between the years A.D. 751 and A.D. 792, were found to
contain certain raw fibres, such as China grass, mulberry, laurel, as
the main constituents, and macerated flax and hemp rags as the minor
constituents.

The addition and substitution of rag evidently increased in course of
time, and since the improvement thus effected soon became an obvious
and established fact, the raw fibres were omitted. Hence the credit
of the manufacture of pure rag paper would be given to the people of
Samarkand, the date being between the years A.D. 760 and A.D. 792; and
further the constitution of such paper has been shown by Dr. Wiesner to
be linen, and not cotton, as commonly stated.

These researches are of such interest that we quote Professor Hoernle's
translation of the summary of the principal results of Dr. Wiesner's
examination of the Eastern Turkestani papers so recently discovered:--

"Taking into account the dates assigned to the papers on palæographic
grounds, the following conclusions may be drawn from the examination of
their material:--

"(1) The oldest of the Eastern Turkestani papers, dating from the
fourth and fifth centuries A.D., are made of a mixture of raw fibres
of the bast of various dicotyledonous plants. From these fibres the
half-stuff for the paper was made by means of a rude mechanical process.

"(2) Similar papers, made of a mixture of raw fibres, are also found
belonging to the fifth, sixth, and seventh centuries. But in this
period there also occur papers which are made of a mixture of rudely
pounded rags and of raw fibres extracted by maceration.

"(3) In the same period papers make their appearance in which special
methods are used to render them capable of being written on, viz.,
coating with gypsum and sizing with starch or with a gelatine extracted
from lichen.

"(4) In the seventh and eighth centuries both kinds of papers are of
equal frequency, those made of the raw fibre of various dicotyledonous
plants and those made of a mixture of rags and raw fibres. In this
period the method of extracting the raw fibre is found to improve from
a rude stamping to maceration; but that of preparing the rags remains a
rude stamping, and in the half-stuff thus produced from rags it is easy
to distinguish the raw fibre from the crushed and broken fibre of the
rags.

"(5) The old Eastern Turkestani (Chinese) paper can be distinguished
from the old Arab paper, not only by the raw fibres which accompany the
rag fibres, but also by the far-reaching destruction of the latter.

"(6) The previous researches of Professor Karabacek and the author had
shown that the invention of rag paper was not made in Europe by Germans
or Italians about the turn of the fourteenth century, but that the
Arabs knew its preparation as early as the end of the eighth century.

"The present researches now further show that the beginnings of the
preparation of rag paper can be traced to the Chinese in the fifth or
fourth centuries, or even earlier.

"The Chinese method of preparing rag paper never progressed beyond its
initial low stage. It was the Arabs who, having been initiated into the
art by the Chinese, improved the method of preparing it, and carried it
to that stage of perfection in which it was received from them by the
civilised peoples of Europe in the mediæval ages.

"(7) The author has shown that the process of sizing the paper with
starch in order to improve it was already known to the Arabs in the
eighth century. In the fourteenth century the knowledge of it was lost,
animal glue being substituted in the place of starch, till finally in
the nineteenth century, along with the introduction of paper machines,
the old process was resuscitated. But the invention of it was due to
the Chinese. The oldest Eastern Turkestani paper which is sized with
starch belongs to the eighth century.

"(8) The Chinese were not only the inventors of felted paper and the
imitators of rag paper--though in the preparation of the latter they
made use of rags only as a surrogate by the side of raw fibres--but
they must also be credited with being the forerunners of the modern
method of preparing 'cellulose paper.' For their very ancient practice
of extracting the fibre from the bark and other parts of plants by
means of maceration is in principle identical with the modern method of
extracting 'cellulose' by means of certain chemical processes."

[Illustration: FIG. 2.--An Early Paper Mill (from "Kulturhistorisches
Bilderbuch," A.D. 1564).]

_Paper-making in Europe._--The introduction of the art into Europe
seems to have taken place early in the eleventh century, when the Moors
manufactured paper at Toledo. The early authorities who have studied
this subject express the opinion that the paper produced in Europe at
this time was made from cotton rags and from raw cotton, but, in view
of the recent researches into the composition of paper, it is difficult
to say how this idea arose, unless we accept the explanation offered by
Professor Karabacek. In standard encyclopædias the following statements
are made as to existing early documents printed on paper made in
Europe:--

  A.D. 1075. Syriac manuscripts of early date in the British
               Museum.

  A.D. 1102. A document printed on cotton, being a deed of King
               Roger of Sicily, now at Vienna.

  A.D. 1178. A treaty of peace between the Kings of Aragon and
               Spain, said to be printed on linen paper, preserved at
               Barcelona.

  A.D. 1223. The "Liber Plegierum," printed on rough cotton
               paper.

One of the most interesting books on this subject is the "Historical
Account of the Substances used to describe Events from the Earliest
Date," by Matthias Koops, published in 1800. This writer appears to
have obtained most of his information from German authorities.

The industry of paper-making passed through Spain into Italy, France,
and the Netherlands. In 1189 paper was being manufactured at Hainault,
in France, and the industry rapidly spread all over the Continent.
In 1390 Ulman Stromer established a mill at Nuremberg, in Germany,
employing a great number of men, who were obliged to take an oath that
they would not teach anyone the art of paper-making or make paper on
their own account. In the sixteenth century the Dutch endeavoured
to protect their industry by making the exportation of moulds for
paper-making an offence punishable by death.

The bulk of the paper used in England was imported from France and
Holland, and it was many years before the industry was established
in England. This is not surprising in view of the protective and
conservative policy of the Continental paper-makers.

[Illustration: FIG. 3.--The Paper Mill of Ulman Stromer, A.D. 1390
(supposed to be the oldest known drawing of a Paper Mill).]

_Paper-making in England._--The actual period at which the manufacture
of paper was first started in England is somewhat uncertain. The
first mention of any paper-maker is found in Wynkyn de Worde's "De
Proprietatibus Rerum," printed by Caxton in 1495, the reference being
as follows:--

        And John Tate the younger, joye mote he brok,
        Which late hathe in England, doo
        Make thys paper thynne,
        That now in our Englyssh
        Thys booke is prynted inne.

John Tate was the owner of a mill at Stevenage, Hertfordshire. In the
household book of Henry VII. an entry for the year 1499 reads, "Geven
in rewarde to Tate of the mylne, 6_s._ 8_d._"

In 1588 a paper mill was erected by Sir John Spielman, a German, who
obtained a licence from Queen Elizabeth "for the sole gathering for ten
years of all rags, etc., necessary for the making of paper." This paper
mill was eulogised by Thomas Churchyard in a long poem of forty-four
stanzas, of which we quote two:--

      I prayse the man that first did paper make,
        The only thing that sets all virtues forth;
      It shoes new bookes, and keeps old workes awake,
        Much more of price than all the world is worth:
      It witnesse bears of friendship, time, and troth,
      And is the tromp of vice and virtue both;
      Without whose help no hap nor wealth is won,
      And by whose ayde great works and deedes are done.

      Six hundred men are set to worke by him
        That else might starve, or seeke abroad their bread,
      Who now live well, and goe full brave and trim,
        And who may boast they are with paper fed.
      Strange is that foode, yet stranger made the same,
      For greater help, I gesse, he cannot give
      Than by his help to make poore folk to live.

The industry made but little progress for some time after Spielman's
death, and up till 1670 the supplies of paper were obtained almost
entirely from France. The first British patent for paper-making was
granted to Charles Hildeyard in 1665 for "the way and art of making
blue paper used by sugar bakers and others." The trade received a great
impetus on account of the presence of Huguenots who had fled to England
from France in consequence of the revocation of the edict of Nantes in
1685.

In 1695 a company was formed in Scotland for the "manufacture of white
and printing paper."

Improvements in the art were slow until 1760, when Whatman, whose name
has since become famous in connection with paper, commenced operations
at Maidstone. Meantime the methods by which the rags were converted
into paper were exceedingly slow and clumsy, so that the output of
finished paper was very small.

Some interesting details as to the early manufacture of paper in
England are given by Mr. Rhys Jenkins, and from his account of "Early
Attempts at Paper-making in England, 1495-1788," the following extracts
have been made:--

  About

  1496. First attempts at paper-making by John Tate at Hertford.

  1496. Tate's paper used by Wynkyn de Worde in "De Proprietatibus
         Rerum."

  1557. A paper mill in existence at Fenditton, Cambridge.

  1569. A mill at Bemmarton, Wilts.

  1574. Mill erected at Osterley, Middlesex, by Sir Thomas Gresham.

  1585. Richard Tottyl asked for sole right to make paper for
         thirty-one years, which was not granted.

  1588. John Spilman erected a mill at Dartford, Kent. Granted a
         patent for sole manufacture of paper.

  1588. Churchyard's poem on the "Paper Myll built near Darthford by
         Master Spilman."

  1612. Robert Heyricke's mill at Cannock Chase, Staffordshire.

  1636. The three or four paper mills in the neighbourhood of Hounslow
         and Colnbrook temporarily shut down on account of the plague,
         the collection of rags having been forbidden.

  1665. Patent granted to Charles Hildeyard for an invention, "the way
         and art of making blew paper used by sugar bakers and others."

  1675. Approximate date of erection of mills at Wolvercote, Oxford,
         where the Oxford India paper is now made.

  1678. Mill at Byfleet, Surrey, mentioned by Evelyn in his diary.

  1682. Bladen--A patent for an engine and process whereby rags are
         wrought into paper.

  1684. Baysmaker--A patent for "the art and mistery of making paper
         in whole sheets."

  1684. Jackson--A patent for "an engine, either for wind or water,
         which prepareth all materials whereof paper may be made."
         Evidently Jackson was acquainted with the "Hollander" beating
         engine.

  1686. A charter granted to the "White Paper Makers' Company" for the
         sole right of making paper exceeding 4_s._ a ream in value.

  1674. Annual importation of paper, presumably from France, stated to
         be 160,000 reams, of average value of 5_s._ (Somers).

  1689. Trade with France prohibited by royal proclamation.

  1696. Price of paper very high owing to scarcity, being 11_s._ per
         ream.

  1712. Duties levied on all kinds of paper, manufactured or imported.

  1725. Monopoly of making paper for Bank of England notes granted to
         De Portal, of the Laverstoke mills, Hampshire. This paper is
         still made by the firm of Messrs. Portal.

  1739. Galliott and Parry estimated that there were 600 paper mills
         in England, making 6,000 reams a day. The Commissioner of
         Excise reported only 278.

  1739. James Whatman erected a mill at Boxley, Maidstone.

  1758. Baskerville printed an edition of Virgil on so-called "woven"
         paper.

_Early Methods._--The most rapid development of the industry appears
to have taken place in Holland. The rags used for paper-making were
moistened with water and stored up in heaps until they fermented
and became hot. By this means the dirt and non-fibrous matter was
rendered partially soluble, so that on washing a suitable paper pulp
was obtained. The washed rags were then placed in a stamping machine
resembling an ordinary pestle and mortar. The mortars were constructed
of stone and wood, and the stamps were kept in motion by levers which
were raised by projections fixed on the shaft of a waterwheel. The
operation of beating thus occupied a long period, but the paper
produced was of great strength.

The invention of the "Hollander," a simple yet ingenious engine which
is deservedly known by the name of the country in which it first
originated, gave a tremendous impetus to the art of paper-making,
as by its means the quantity of material which could be treated in
twenty-four hours was greatly increased. Unfortunately the date of the
invention of this important machine has not been definitely traced. The
earliest mention of it seems to occur in Sturm's "Vollständige Mühlen
Baukunst," published in 1718. It was in extensive use at Saardam in
1697, so that the invention is at least some years previous to 1690.

On this point Koops says: "In Gelderland are a great many mills, but
some so small that they are only able to make 400 reams of paper
annually, and there are also water mills with stampers, like those
in Germany. But in the province of Holland there are windmills,
with cutting and grinding engines, which do more in two hours than
the others do in twelve. In Saardam 1,000 persons are employed in
paper-making."


THE FIRST FOURDRINIER PAPER MACHINE.

Up till the year 1799 paper was made entirely in sheets on a hand
mould, but during the last few years of the eighteenth century a
Frenchman, Nicholas Louis Robert, manager for M. Didot, who owned a
paper mill at Essones, had been experimenting for the purpose of making
paper in the form of a continuous sheet, and eventually produced some
of considerable length.

The idea was taken to England by Didot's brother-in-law, Gamble, and
introduced to the notice of Messrs. Fourdrinier, wholesale stationers,
of London.

[Illustration: FIG. 4.--The First Paper Machine, A.D. 1802. Plan and
Elevation.]

The first machine was naturally a very crude affair. It consisted of an
endless wire cloth stretched in a horizontal position on two rollers,
one of which rotated freely in a bearing attached to the frame of the
machine, the other being fitted in an adjustable bearing so that the
wire could be tightened up when necessary.

The beaten pulp, contained in a vat placed below the wire, was thrown
up in a continual stream upon the surface of the wire, and carried
forward towards the squeezing rolls. A shaking motion was imparted to
the travelling wire so as to cause the fibres to felt properly. A great
deal of the water fell through the meshes of the gauze, and further
quantities were removed by means of the press rolls. The wet paper was
then wound up on to a wooden roller, which was taken out as soon as
sufficient paper had been made.

[Illustration: FIG. 5.--The Improved Paper Machine of A.D. 1810.]

The whole process was carried on under great difficulties, but
substantial improvements were soon made by the enterprising
Fourdriniers, who commenced operations in Bermondsey, employing Mr.
Bryan Donkin, then in the service of Messrs. Hall & Co., of Dartford,
who had shown himself keenly interested in the machine. In 1803 the
first "Fourdrinier," so called, was built at Bermondsey, and erected at
Two Waters Mill in Herefordshire.

In this machine the mixture of pulp and water was carried forward
between two wires, and, after passing through the couch rolls,
transferred to an endless felt. This arrangement proved to be faulty
because the water did not escape freely enough from the wire, and a
great deal of the paper was spoilt.

Donkin, however, hit upon a simple but effective device for curing this
fault by altering the relative position of the two couch rolls. Instead
of keeping the two rolls exactly in a vertical position one over the
other, he placed them at a slight angle so that the upper one should
bear gently on the web of paper carried by the wire before receiving
the full pressure of the rolls, and thus remove a greater proportion of
the water. In this way the paper was firmer and less liable to break
when pressed between the couch rolls, an additional advantage being
secured in the fact that the upper wire could be dispensed with.

The various improvements effected resulted in a machine the details of
which appear in the appended diagram, the device of the inclined couch
rolls being fitted about 1810.

The mixture of water and pulp flowed from a stuff chest into a small
regulating box and on to the wire over a sloping board. The pulp at
once formed into a wet sheet of paper, the water falling through the
meshes of the wire, being caught in a bucket-shaped appliance, and
conveyed back to the regulating box. The stream of pulp was confined
upon the wire by means of a deckle. Further quantities of water were
removed by the aid of a pair of squeezing rolls before the web passed
through the couch rolls after which the paper was reeled up on a wooden
spindle.

From this date the success of the machine was assured, though the
inventor and his colleagues were practically ruined, an experience only
too common with the early pioneers of many great and useful industrial
enterprises. In fact, the firm of Messrs. Donkin were the only people
to profit from the invention, for they manufactured a number of
machines, as stated in the report of the Jurors of the Exhibition of
1851, and from 1803 to 1851 no less than 190 Fourdriniers were set to
work.




CHAPTER II

CELLULOSE AND PAPER-MAKING FIBRES


When plants such as flax, cotton, straw, hemp, and other varieties of
the vegetable kingdom are digested with a solution of caustic soda,
washed, and then bleached by means of chloride of lime, a fibrous mass
is obtained more or less white in colour.

This is the substance known to paper-makers as paper pulp, and the
several modifications of it derived from different plants are generally
known to chemists as cellulose.

Although plants differ greatly in physical structure and general
appearance, yet they all contain tissue which under suitable treatment
yields a definite proportion of this fibrous substance. The preparation
of a small quantity of cellulose from materials like straw, rope,
hemp, the stringy bark of garden shrubs, wood, and bamboo can easily
be accomplished without special appliances. Soft materials, such as
straw and hemp, are cut up into short pieces, hard substances like
wood and bamboo are thoroughly hammered out, in order to secure a fine
subdivision of the mass. The fibre so prepared is then placed in a
small iron saucepan, and covered with a solution made up of ten parts
of caustic soda and 100 parts of water. The material is boiled gently
for eight or ten hours, the water which is lost through evaporation
of steam being replaced by fresh quantities of hot water at regular
intervals. When the fibrous mass breaks up readily between the fingers,
it is poured into a sieve, or on a piece of muslin stretched over
a basin, and washed completely with hot water until clean and free
from alkali. Hard pieces and portions which seem incompletely boiled
are removed, and the residual fibres separated out. These fibres are
placed in a weak, clear solution of ordinary bleaching powder, left for
several hours, and subsequently thoroughly washed. This simple process
will give a more or less white fibrous material.

The purest form of cellulose is cotton. A very slight alkaline
treatment, followed by bleaching, is sufficient to remove the
non-fibrous constituents of the plant, and a large yield of cellulose
is obtained. For this reason the cotton fibre ranks high as an almost
ideal material for paper-making, possessing the quality of durability.

Cellulose is an organic compound, containing carbon, hydrogen, and
oxygen in the following proportions:--

          Carbon           44·2
          Hydrogen          6·3
          Oxygen           49·5
                          -----
                          100·0

Its composition is represented by the formula C_{6}H_{10}O_{5}.

The celluloses obtained from various plants are not identical either in
physical structure and chemical constitution, or as to their behaviour
when employed for paper-making. In fact, the well-known differences
between the raw materials used for paper-making, and also between the
numerous varieties of finished paper, are to be largely accounted for
and explained by a careful study of the cellulose group, particularly
with reference to the microscopic characteristics and the chemical
composition of the individual species.

The only vegetable substance which may be regarded as a simple
cellulose is cotton, all others being compound celluloses of varying
constitution, the nature of which cannot be appreciated without a
considerable knowledge of chemistry. The classification of such plants,
therefore, in a book of this description must be limited to certain
distinctions having some immediate practical bearing on the question of
paper manufacture.

_Cotton._--Regarded as the typical simple cellulose, containing 91 per
cent. of cellulose, and remarkable for its resistance to the action of
caustic soda.

_Linen._--The cellulose isolated from flax by treatment with alkali or
caustic soda cannot readily be distinguished from cotton cellulose by
chemical analysis or reactions. The difference is almost entirely a
physical one.

Flax is a typical compound cellulose, to which has been given the name
pecto-cellulose on account of certain properties. Other well-known
plants of this class are ramie, aloe, "sunn hemp," manila.

_Esparto._--The cellulose isolated from esparto differs in composition
from cotton cellulose:--

          Carbon                       41·0
          Hydrogen                      5·8
          Oxygen                       53·2
                                      -----
                                      100·0
                                      -----

It is regarded as an oxycellulose, being readily oxidised by exposure
to air at 100° C. Other oxycelluloses familiar to the paper-maker are
straw, sugarcane, bamboo.

_Wood._--The difference between wood and the plants already mentioned
is expressed by the term lignified fibre or ligno-cellulose. This term
is used to indicate that the wood is a compound cellulose containing
non-fibrous constituents, to which has been given the name lignone.
Jute is another example of this class.

       *       *       *       *       *

These distinctions may be exemplified by reference to a simple
experiment. If three papers, such as a pure rag tissue or a linen
writing, an ordinary esparto printing, and a cheap newspaper containing
about 80 per cent. of mechanical wood, are heated for twenty-four
hours in an oven at a temperature of 105° C., the first will undergo
little, if any, change in colour, while the others will be appreciably
discoloured, the mechanical wood pulp paper most of all.

This change is due to the gradual oxidation of the constituents of
the paper, the ligno-cellulose of the mechanical wood pulp being most
readily affected by the high temperature, and the pure cellulose of the
rag paper being least altered.

The process of oxidation, brought about rapidly under the conditions of
the experiment described, takes place in papers of low quality exposed
to air in the ordinary circumstances of daily use, but of course at an
extremely slow rate. The deterioration of such paper is not, however,
due to the simple oxidation of the cellulose compounds, because other
factors have to be taken into account. The presence of impurities in
the paper on the one hand, and of chemical vapours in the air on the
other, hastens the decay of papers very considerably.

_Percentage of Cellulose in Fibrous Plants._--The value of a vegetable
plant for paper-making is first determined by a close examination
of the physical structure of the cellulose isolated by the ordinary
methods of treatment. If the fibres are weak and short, the raw
material is of little value, and it is at once condemned without
further investigation, but should the fibre prove suitable, then the
question of the percentage of cellulose becomes important.

There are several methods employed for estimating the amount of
cellulose in plants. The process giving a maximum yield is known as the
chlorination method, the details of which are as follows:--About ten
grammes of the air-dried fibre is dried at 100° C. in a water oven for
the determination of moisture. A second ten grammes of the air-dried
fibre is boiled for thirty minutes with a weak solution of pure caustic
soda (ten grammes of caustic soda in 1,000 cubic centimetres of water),
small quantities of distilled water being added at frequent intervals
to replace water lost by evaporation. The residue is then poured on to
a piece of small wire gauze, washed thoroughly, and squeezed out. The
moist mass of fibre is loosened and teased out, placed in a beaker,
and submitted to the action of chlorine gas for an hour. The bright
yellow mass is then washed with water and immersed in a solution of
sodium sulphite (twenty grammes of sodium sulphite in 1,000 cc. of
water). The mixture is slowly heated, and finally boiled for eight to
ten minutes, with the addition of 10 cc. of caustic soda solution. The
residue is washed, immersed in dilute sodium hypochlorite solution
for ten minutes, again washed, first with water containing a little
sulphurous acid and then with pure distilled water. It is finally dried
and weighed.

The second process for estimating cellulose is based upon the use
of bromine and ammonia. About ten grammes of the air-dried fibre is
placed in a well-stoppered wide-mouthed bottle with sufficient bromine
water to cover it. As the reaction proceeds the red solution gradually
decolourises, and further small additions of bromine are necessary. The
mass is then washed, and boiled in a flask connected to a condenser
with a strong solution of ammonia for about three to four hours. The
fibrous residue is washed, again treated with bromine water in the
cold, and subsequently boiled with ammonia. The alternative treatment
with bromine and ammonia is repeated until a white fibrous mass is
obtained.

In practice the paper-maker is confined to two or three methods for the
isolation of the fibres, viz., alkaline processes, which require the
digestion of the material with caustic soda, lime, lime and carbonate
of soda, chiefly applied to the boiling of rags, esparto, and similar
pecto-celluloses; acid processes, in which the material is digested
with sulphurous acid and sulphites. The latter methods are at present
almost exclusively used for the preparation of chemical wood pulp.

_Yields of Cellulose in the Paper Mill._--The object of the paper-maker
is to obtain a maximum yield of cellulose residue at a minimum of cost.
Usually the amount of actual bleached paper pulp obtained in the mill
is less than the percentage obtained by careful quantitative analysis,
for reasons easily understood.

In the first place, the raw material is digested for a stated period
with a carefully measured quantity of caustic soda, for example, at
a certain temperature. Now the conditions of boiling may be varied
by altering one or more of these factors, the period of boiling, the
strength of solution, or the steam pressure, and the paper-maker must
exercise his judgment in fixing the exact relation between the varying
factors so as to produce the best results.

In the second place, the mechanical devices for washing the boiled
pulp and for bleaching cause slight losses of fibre, which cannot be
altogether avoided when operations are conducted on a large scale.
Frequently, also, a greater yield of boiled material may involve
a larger quantity of bleaching powder, so that it is evident the
adjustment of practical conditions requires considerable technical
skill and experience.

The percentage of cellulose in the vegetable plants employed more or
less in the manufacture of paper is given in the following table:--

TABLE SHOWING PERCENTAGE OF CELLULOSE IN FIBROUS PLANTS.

          ------------------+-------------------------
             Fibre.         |   Cellulose, per cent.
          ------------------+-------------------------
          Cotton            |         91·0
          Flax              |         82·0
          Hemp              |         77·0
          Ramie             |         76·0
          Manila            |         64·0
          Jute              |         64·0
          Wood (pine)       |         57·0
          Bagasse           |         50·0
          Bamboo            |         48·0
          Esparto           |         48 to 42
          Straw             |         48 to 40
          ------------------+-------------------------

_The Properties of Cellulose._--Cellulose is remarkably inert towards
all ordinary solvents such as water, alcohol, turpentine, benzene,
and similar reagents, a property which renders it extremely useful in
many industries, with the result that the industrial applications of
cellulose are numerous and exceedingly varied.

_Solubility._--Cellulose is dissolved when brought into contact with
certain metallic salts, but it behaves quite differently to ordinary
organic compounds. Sugar, for example, is a crystalline body soluble
in water, and can be recovered in a crystalline state by gradual
evaporation of the water. Cellulose under suitable conditions can be
dissolved, but it cannot be reproduced in structural form identical
with the original substance.

If cellulose is gently heated in a strong aqueous solution of zinc
chloride, it gradually dissolves, a thick syrupy mass being obtained,
which consists of a gelatinous solution of cellulose. If the mixture
is diluted with cold water, a precipitate is produced consisting of
cellulose hydrate intimately associated with oxide of zinc, which
latter can be dissolved out by means of hydrochloric acid. The
resulting product is not, however, the original substance, but a
hydrated cellulose, devoid of any crystalline structure.

Cellulose is also soluble in ammoniacal solutions of cupric oxide, from
which it can be precipitated by acids or by substances which act as
dehydrating agents, _e.g._, alcohol.

_Hydrolysis._--An explanation of the behaviour of cellulose towards the
solvents already mentioned, and towards acid and alkali, requires a
reference to its chemical composition.

The substance is a compound of carbon, hydrogen, and oxygen represented
by the formula

                                C_{6}H_{10}O_{5}

being one of a class of organic compounds known as carbohydrates,
so designated because the hydrogen and oxygen are present in the
proportions which exist in water.

                      Water = Hydrogen + Oxygen
                                H_{2}  +  O.

The H_{10}O_{5} in the cellulose formula corresponds to 5 (H_{2}O).

When cellulose is acted upon by acid, alkali, and certain metallic
salts, it enters into combination with one or more proportions of
water, forming cellulose hydrates of varying complexity. This change is
usually termed hydrolysis.

With mineral acids like sulphuric and hydrochloric acids, cellulose,
if boiled in weak solutions, is converted into a non-fibrous brittle
substance having the composition

                    C_{12}H_{20}O_{10} 2 H_{2}O

to which the name _hydra-cellulose_ has been given. Similar changes
occur, but at a much slower rate, when cellulose is in contact with
free acids at ordinary temperatures. For this reason it is important
that paper, when finished, should not be contaminated with free acid.

The nature and extent of the chemical change can be varied by altering
the strength of the acid and the conditions of treatment. The
manufacture of _parchment_ paper is an example of the practical utility
of the chemical reaction between cellulose and acid. A sheet of paper
is dipped into a mixture of three parts of strong sulphuric acid and
one part of water, when it becomes transparent. Left in the solution it
dissolves, but if taken out and dipped into water in order to wash off
the acid the reaction is stopped, and a tough semi-transparent piece of
_parchment_ is obtained. The cellulose is more or less hydrated, having
the composition

                C_{12}H_{20}O_{10} H_{2}O,

a substance having the name _amyloid_.

_Oxidation._--Cellulose is only oxidised to any appreciable extent by
acid and alkali if treated under severe conditions. It is remarkable
that the processes necessary for isolating paper pulp from plants when
digested with these chemical reagents do not act upon or destroy the
fibre, and this capacity for resisting oxidation has rendered cellulose
extremely valuable to many of the most important industries.

The resistant power of the cellulose is, however, broken down by the
use of acid and alkali in concentrated form.

Oxalic and acetic acids are obtained when cellulose is heated strongly
at 250° C. with solid caustic soda.

Oxy-cellulose, a white friable powder, is produced by means of strong
mineral acids. Nitric acid at 100° C. attacks the fibre very readily
and produces about 30-40 per cent. of the oxidised cellulose.


CELLULOSE DERIVATIVES.

The great number of compounds and derivatives, _i.e._, substances
obtained by chemical treatment, may be judged from the following list.
The substances of commercial importance are suitably distinguished from
those of merely scientific interest by the printing of the names in
small capitals.

  ACETIC ACID.--An important commercial product obtained by the
      destructive distillation of wood. The crude pyroligneous acid is
      first neutralised with chalk or lime, and the calcium acetate
      formed then distilled with sulphuric acid. Wood yields 5 to 10
      per cent. of its weight of acetic acid according to the nature of
      the wood.

  ACETONE.--A solvent for resins, gums, camphor, gun cotton, and other
      cellulose products. Prepared by distilling barium or calcium
      acetate in iron stills, the acetate being obtained from the crude
      acetic acid produced by the dry distillation of wood.

  _Acid Cellulose._--(See Hydral-Cellulose.)

  _Adipo-Cellulose._--A distinct compound cellulose present in the
      complex cuticular tissue of plants, and separated easily by
      suitable solvents from the wax and oily constituents also present.

  ALKALI CELLULOSE.--When cotton pulp is intimately mixed with strong
      caustic soda solution, this compound is formed. It is utilised in
      the manufacture of _Viscose_.

  _Amyloid._--Strong sulphuric acid acts upon cellulose and converts it
      into a gelatinous semi-transparent substance to which the name
      amyloid has been given. (See Parchment Paper.)

  BALLISTITE.--A smokeless powder composed of nearly equal parts of
      nitro-glycerine and nitrated cellulose, with a small quantity of
      diphenylamine.

  _Carbohydrate._--A large number of important commercial products,
      such as cellulose, sugars, starches, and gums, consist of the
      elements carbon, hydrogen, and oxygen, associated in varying
      proportions. The ratio of hydrogen to oxygen in these compounds
      is always 2:1 (H_{2} and O).

                    Cellulose    C_{6}H_{10}O_{5}.
                    Sugar        C_{6}H_{12}O_{6}.
                    Dextrin _n_ (C_{6}H_{10}O_{5}).

  To all these substances the term carbohydrate is applied.

  _Celloxin_ (Tollens).--A substance having the stated composition
      C_{8}H_{6}O_{6} considered to be present in oxidised derivatives
      of cellulose.

  CELLULOID.--This well-known material is made by incorporating camphor
      with nitro-cellulose, a plastic ivory-like substance being
      produced. In practice the process is as follows:--Wood pulp or
      wood pulp paper is saturated with a mixture of sulphuric acid
      (five parts) and nitric acid (two parts), which produces nitrated
      cellulose. The product is washed, ground, and mixed with camphor,
      the mastication being effected by heavy iron rollers. The mass
      thickens and can be removed in the form of thick sheets. These
      sheets are submitted to great pressure between steam-heated
      plates. The cake obtained is cut into sheets of any desired
      thickness, seasoned by prolonged storage, and afterwards worked
      up into boxes, combs, brush-backs, and many other domestic
      articles of a useful and ornamental character.

  CELLULOSE ACETATE (Cross).--If cellulose is heated with acetic
      anhydride at 180° C., viscous solutions of the acetates are
      obtained. The process yielding a definite acetate of commercial
      value is based upon the following reaction:--100 parts of
      cellulose prepared from the sulpho-carbonate are mixed with
      120 parts of zinc acetate, heated and dried at 105° C. Acetic
      anhydride is added in small quantity, and 100 parts of acetyl
      chloride. At a temperature of 50° C. the mixture becomes liquid,
      and cellulose acetate is subsequently obtained as a white powder.

  The compound can be used in the place of cellulose nitrate, and,
      being non-explosive, may gradually replace the latter in many
      industrial applications.

  _Cellulose-Benzoate._--When alkali cellulose is heated with benzoyl
      chloride and excess of caustic soda, this substance is obtained.

  _Cellulose Hydrate._--The substances produced by the action of acid
      and alkali on cellulose under certain strictly defined conditions
      are bodies containing cellulose united with water to form
      hydrates. The industrial applications of cellulose based upon
      this reaction are described under the special headings.

  CELLULOSE NITRATE.--A considerable number of derivatives are obtained
      by bringing cellulose into contact with nitric acid. Variations
      in the strength of the acid, the temperature of reaction, and the
      time of contact determine the nature of the product. The best
      known nitrates are:--

        Cellulose di-nitrate.

        Cellulose tri-nitrate and tetra-nitrate, present chiefly in
          pyroxyline.

        Cellulose penta-nitrate.

        Cellulose hexa-nitrate, the chief constituent of gun-cotton.

  CHARCOAL.--Not a cellulose derivative in the strict sense of the
      term, charcoal being a residue obtained in the dry distillation
      of wood.

  COLLODION.--A soluble nitrate of cellulose used in photography. (See
      Pyroxyline.)

  CORDITE.--A smokeless powder consisting mainly of nitro-glycerine
      and gun-cotton mixed with acetone. The materials are thoroughly
      incorporated and the resultant paste formed into threads which
      are dyed and then cut up into suitable lengths for cartridges.

  _Cuto-Cellulose._--Synonymous with adipo-cellulose.

  _Dextron._--A compound prepared from the waste liquors of the
      bisulphite process used for the manufacture of wood pulp.
      Resembles dextrin in its physical properties.

  DEXTROSE.--A carbohydrate which can be obtained by the action of
      mineral acids on cellulose. Commercial dextrose, or glucose, is
      prepared by the conversion of starch with sulphuric acid. The
      starch is mixed with dilute acid at a fixed temperature, and the
      starch milk obtained poured gradually into a vessel containing
      dilute acid, which is maintained at boiling point. The conversion
      is complete and rapid.

  EXPLOSIVES.--The production of the several cellulose nitrates has
      given rise to a great number of highly explosive substances.

        _Blasting Gelatine._--A mixture of nitro-glycerine with
      cellulose nitrates.

        _Amberite_, _Ballistite_, _Cordite_, and other smokeless
      powders, consisting of nitro-glycerine and cellulose nitrates in
      about equal proportions.

        _Sporting powders_ made by mixing nitro-cellulose with
      barium nitrate, camphor nitro-benzene, such as _indurite_,
      _plastomenite_, etc.

  GLUCOSE.--(See Dextrose.)

  GUN-COTTON.--An explosive prepared by the action of nitric acid on
      cotton. Selected cotton waste suitably opened up is immersed
      in a mixture of three parts of nitric acid by weight (1·50 sp.
      gr.) and one part of sulphuric acid by weight (1·85 sp. gr.) and
      submitted to a number of processes by which the nitration is
      properly effected so as to produce a nitro-cellulose of uniform
      composition. The material is washed, reduced to pulp, and moulded
      into various forms.

  _Hemi-Cellulose._--The constituents of plant tissues are extremely
      varied in character. Many plants contain substances which
      resemble true cellulose, but differing from it in being easily
      converted by hydrolysis, and by the action of dilute acids,
      into carbohydrates. Plants which contain a large proportion of
      such constituents are termed hemi-celluloses. In some cases
      certain crystallisable sugars can be obtained by hydrolysis under
      suitable conditions.

  _Hydral-Cellulose_ (Bumcke).--A compound of merely scientific
      interest, resulting from the treatment of cellulose with hydrogen
      peroxide. When acted upon by alkali it is decomposed into
      cellulose and acid cellulose, the latter a derivative of unstable
      composition.

  _Hydro-Cellulose._--This product, a white, non-structureless, friable
      powder, is obtained by treating cellulose with hydrochloric or
      sulphuric acid of moderate strength. The substance itself has
      no commercial value, but the reaction is useful in separating
      cotton from animal fabrics. If a woollen cloth containing cotton
      is soaked in dilute sulphuric acid, washed, and dried at a gentle
      heat, the cotton is acted upon, and can be beaten out of the
      fabric, the wool resisting the acid treatment.

  _Lignin._--The complex mixture of substances which is associated
      with cellulose in wood, jute, and other _ligno-celluloses_. The
      conversion of wood into chemical pulp effects the removal of this
      material more or less completely. The well-known "phloroglucine"
      test for mechanical wood in papers is based upon the presence of
      _lignin_ in the wood.

  _Ligno-Cellulose._--Wood and jute are typical bodies consisting of
      cellulose and complex non-cellulose, generally described as
      lignin, associated together in the plant tissue. The chemistry
      of the non-cellulose portion of wood is a matter still under
      investigation, its importance from a commercial point of view
      being obvious from the fact that the removal of the _lignin_
      during the conversion of the wood into wood-cellulose results in
      a loss of 50 per cent. of the weight of wood.

  _Lustra-Cellulose._--Synonymous with and suggested as a more
      appropriate name for the material usually described as
      _artificial silk_.

  MERCERISED COTTON.--When cotton is immersed in strong solutions of
      caustic soda a remarkable change sets in. The physical structure
      of the fibre is entirely altered from the long flattened tube
      having a large central canal to a shorter cylindrical tube in
      which the canal almost disappears. Hydration of the cellulose
      takes place, and these changes are taken advantage of in the
      production of mercerised cloth (so named from the discoverer of
      the reaction, Mercer). Cotton goods, particularly those made of
      long stapled cotton, when mercerised, exhibit a beautiful lustre,
      and some magnificent crêpon effects are obtained by the process.

  _Methoxyl._--A constituent of the complex compound known as
      ligno-cellulose, which is present in wood and similar fibres.
      The amount of methoxyl in lignified tissue can be accurately
      determined, and it has been suggested that the proportion of
      methoxyl found in a cheap printing paper could be used as a
      measure of mechanical wood pulp present.

  _Muco-Cellulose._--This term is applied to certain compound
      celluloses present chiefly in mucilages, gums, and in
      seaweeds (Algæ). The natural substances are all of commercial
      importance--Iceland moss, Carragheen, Algin, etc.

  NAPHTHA.--One of the products of the dry distillation of wood,
      usually described as wood-naphtha, or wood spirit.

  NITRO-CELLULOSE.--The treatment of cellulose with nitric acid gives
      a number of nitro-celluloses according to the conditions of the
      process. (See Cellulose Nitrates.)

  OXALIC ACID.--A substance of great commercial importance prepared
      by heating the sawdust of soft wood, such as pine, fir, and
      poplar, with strong solutions of mixed caustic soda and potash
      to dryness. The wood yields after six hours a greyish mass
      containing about 20 per cent. of the acid, which is separated out
      by water and then crystallised.

  It is used for bleaching, and as a _discharge_ in calico printing
      and dyeing.

  _Oxy-Cellulose._--A white friable powder produced by treating
      cellulose with nitric acid at 100° C. The oxidation of cellulose
      is brought about by several reagents such as chromic acid,
      hypochlorites of lime and soda, chlorine, and permanganates. The
      extent to which cloth has been damaged by overbleaching may be
      determined by a simple test with methylene blue solution, which
      is readily absorbed by oxy-cellulose present in such fabrics.

  PARCHMENT.--A tough paper prepared by the action of sulphuric acid on
      unsized paper. (See page 137.)

  _Pectins._--(See Pecto-Cellulose.)

  _Pecto-Cellulose._--A generic term applied to many important fibrous
      materials, such as flax, straw, esparto, bamboo, phormium,
      ramie, &c., which on alkaline treatment yield cellulose for
      paper-making, and a non-fibrous soluble residue of complex
      composition. These soluble derivatives are known as pectin
      (C_{32}H_{48}O_{32}), pectic acid (C_{32}H_{44}O_{30}), and
      metapectic acid (C_{32}H_{28}O_{36}). Although the soluble
      constituents of the pecto-celluloses amount to 50 per cent. by
      weight in most cases, no process for the recovery of the product
      in a commercial form has yet been devised. (See description of
      Soda recovery, page 78.)

  PYROXYLINE.--A substance prepared by nitrating cotton. The cotton is
      immersed in a mixture of nitric and sulphuric acids of carefully
      regulated strength, and subsequently washed free of the acid.
      Three volumes of nitric acid (sp. gr. 1·429) are diluted with
      two volumes of water and nine volumes of strong sulphuric acid
      (sp. gr. 1·839) added. To the solution when cool the cotton is
      added in small quantities at a time. The resultant pyroxyline
      is soluble in a mixture of equal quantities of alcohol and
      ether, and in the soluble form is utilised as _collodion_ for
      photography.

  SILK, ARTIFICIAL.--A remarkable substance made from wood or cotton
      cellulose, closely resembling silk in appearance and physical
      properties.

        Nitrated cellulose is dissolved in a mixture of equal parts of
      alcohol and ether.

        The solution is forced through five capillary tubes under
      high pressure, and the filament so obtained solidifying at once
      is wound together with other similar filaments upon suitable
      bobbins. Various modifications of this general process are in
      use, such as the solidification of the solution into threads
      by passing it into water; the application of solvents less
      inflammable than ether and alcohol; the use of other forms of
      dissolved cellulose such as those prepared by means of zinc
      chloride, ammoniacal copper oxide, or acetic anhydride. In
      all cases the yarn or thread is submitted to further chemical
      treatment for the removal of nitric acid and to render the
      material non-explosive and less inflammable. The finished product
      is soft and supple, can be easily bleached and dyed, and is
      capable of acquiring a high lustre.

  SMOKELESS POWDERS.--(See Explosives.)

  _Sulpho-Carbonate._--(See Viscose.)

  SULPHATE CELLULOSE.--Chemical wood pulp prepared by the sulphate
      process. (See page 107.)

  SULPHITE CELLULOSE.--Chemical wood pulp prepared by the sulphite
      process. (See page 107.)

  VISCOSE.--A soluble sulpho-carbonate of cellulose, prepared by
      treating cellulose with a 15 per cent. solution of caustic soda,
      and shaking the product with carbon bisulphide in a closed
      vessel. The mixture forms a yellowish mass soluble in water,
      giving a viscous solution which has some remarkable and valuable
      properties.

        This _viscose_, on standing, coagulates to a hard mass which
      can be turned and polished.

        If spread on glass and coagulated by heat, films are obtained
      from which the alkaline by-products can be washed out. These
      films are transparent, colourless, very tough and hard.

  VULCANISED FIBRE.--Fibre or pulp treated with zinc chloride in acid
      solution, or otherwise, for the manufacture of hard boards. (See
      page 139.)

  WILLESDEN GOODS.--Paper, fibre, and textiles when treated with
      cuprammonium oxide are partially gelatinised on the surface and
      rendered waterproof. (See page 139.)

  _Wood Spirit._--(See Naphtha.)

  _Xylonite._--(See Celluloid.)


FIBRES FOR PAPER-MAKING.

Although the vegetable world has been explored from time to time for
new supplies of cellulose, and some plants have been found serviceable
in certain directions, yet the number of fibres in actual use is very
limited.

The following table indicates the principal sources of the material
required for paper-making:--

  --------+----------------------------+--------------------------------
   Fibre. |    Source of the Fibre.    |   Application of the Fibre.
  --------+----------------------------+--------------------------------
  Linen   | Rags, textile waste.       | High class writings and
          |                            | printings.
  Cotton  | Rags, textile waste.       | High class writings and
          |                            | printings.
  Esparto | Natural grass.             | Writings and printings.
  Straw   | Straw from various         | Printings, box and card boards.
          | cereals--wheat, barley,    |
          | oats, etc.                 |
  Wood    | Mechanically ground wood.  | Cheap papers, boxboards,
          |                            | middles, tickets and cards,
          |                            | writings and printings.
    "     | Chemically prepared wood.  | Writings and printings.
  Flax    | Threads, waste from        | Wrappings, boards, cable
          | spinning mills.            | papers.
  Hemp    | Spinning refuse, old rope, | Wrappings, boards, cable
          | sailcloth, etc.            | papers, strong writings.
  Jute    | Waste, old gunny bags.     | Wrappings, boxboard, cards.
  Bamboo  | Natural stems.             | Writings and printings (not in
          |                            | Europe, and only limited
          |                            | quantities elsewhere).
  Ramie   | Bast fibres of the plant;  | Rarely used, except in special
          | textile refuse.            | cases.
  Bagasse | Sugar-cane refuse.         | Common papers (chiefly
          |                            | experimental results).
  Manila  | Textile and rope refuse.   | Wrappings, cable papers.
    Hemp  |                            |
  --------+----------------------------+--------------------------------

_Exploiting New Fibres._--The exploitation of any new paper-making
fibre requires attention to certain important details, which may be
fairly considered in the following order:--

(1) _Supply._--The supply of material must be plentiful and obtainable
in large quantities. Too often this question is entirely neglected by
those who bring new fibres to the notice of paper-makers, probably
because they do not realise that enormous quantities of material are
necessary to supply even a very small section of the paper trade,
the fact being that few plants yield more than half their weight of
paper-making fibre.

(2) _Suitability._--The fibre should be properly examined as to
its chemical and physical properties in a laboratory equipped with
appliances for its conversion into bleached paper pulp on a small
scale. The examination of the fibre would include tests as to the
amount of pulp which can be obtained from one ton of raw material, the
approximate cost of treatment, and details as to the value of the fibre
for paper-making.

(3) _Cost of Raw Material._--If the supply of material seems to be
sufficient, and the paper pulp obtained possesses suitable qualities,
then it is necessary to get accurate information as to the cost of the
fibre delivered to some given spot at or near the place of collection.

The exploitation of any new fibre for paper-making purposes will
involve a recognition of the fact that the raw material must be
converted into pulp at or near the place where the material is most
abundant.

The only interesting exception to this is the case of esparto
fibre, which is imported into England in large amount, but this is
only possible because esparto possesses most valuable paper-making
qualities, and is obtained in countries close to England, where large
quantities are consumed. It is doubtful whether other fibres could be
utilised in the same way.

(4) _The Cost of Manufacture_ at or near the place of collection
requires to be carefully worked out, due consideration being given
to the actual cost of chemicals on the spot, cost of labour, and the
conditions under which the maintenance of machinery can be efficiently
looked after.

(5) _Carriage and Freight Charges_ are the last, but by no means the
least, items of importance. It is not too much to say that the whole
success of the exploitation of new paper-making fibre hangs entirely
upon this item, the majority of many fibres which have been brought to
the notice of the trade being suitable, but impracticable, solely on
account of these and similar commercial considerations.

In the pages of the trade press for the last few years the following
fibres have been noticed:--

(1) _Flax Pulp._--This material was to be obtained from flax straw.
Attempts were made on a commercial scale to produce quantities of flax
fibre, but so far the efforts made have not been very successful.

(2) _Ramie Fibre._--This material has been exploited over and over
again, chiefly for textile trades, its application as a paper-making
material being limited to small quantities used for special purposes
such as bank notes. The fibre is too valuable, except for textile
industries, and can only come into the paper trade as a waste material
from such sources.

(3) _Tobacco Fibre_ has been before the trade for some years, the
idea being to utilise tobacco stems and other tobacco waste for
the manufacture of paper suitable for use as wrappers for cigars,
cigarettes, and similar purposes.

(4) _Agave Fibre._--This name is given to a large and important genus
of fibre-yielding plants found chiefly in Central America. It is also
found in India, and in 1878 an experiment was made for the manufacture
of paper at a mill near Bombay, but this did not give any satisfactory
results, probably on account of the primitive methods used in treatment.

(5) _Bagasse._--The waste material from sugar-cane has been looked upon
for many years as a desirable fibre, much time and labour having been
given to the utilisation of this material. In spite of these efforts
bagasse still remains an almost useless and unworkable material. This
is partly due to inferiority of the pulp and partly due to difficulties
connected with its treatment. Probably cultivation of the plant for the
sake of its fibre instead of the sugar might give better results.

(6) _Peat._--The attempts made to utilise peat for paper-making are
probably fresh in the minds of those paper-makers interested in the
production of wrappers and boxboards. The nature of peat, however, is
such as to exclude the hope of making any useful article. The material
has been exploited by companies in Austria, Ireland, and Canada on a
fairly large scale, with but a limited amount of success.

(7) _Cotton-seed Hulls._--Many patents have been taken out for the
chemical treatment of cotton-seed waste and having for their object the
removal of the particles of seed hulls, so as to obtain a pure cotton
pulp. The scheme sounds attractive, but there are so many conditions
which have to be taken account of that the commercial success of any
undertaking based on the use of cotton-seed hulls is very questionable.
The fact is that the hulls have a market value quite apart from the
possibility of their application to paper-making, and this initial cost
would prevent paper-makers from buying the material owing to the large
quantity necessary for the manufacture of one ton of pure pulp.

(8) _Apocynum._--This plant is said to be utilised to some extent by
the Russian Government in the manufacture of bank notes, the plant
being cultivated at Poltava. This is an instance of the particular
application of a fibrous material in limited quantities, a proposition
which is always feasible in the case of special requirements.

(9) _Cornstalk._--This fibre has been chiefly exploited in America,
experts having been attracted by the enormous quantities of cornstalk
available in the several wheat-producing States. The manufacture
of paper pulp from this material on a large scale has yet to be
established.

(10) _Japanese Paper Fibres._--In Eastern countries a great number of
fibrous plants are utilised in small quantities for the manufacture
of special papers. It is obvious that in these Eastern countries the
employment of fibres which are not cultivated in large bulk is readily
possible when the question of price obtained for the paper and the
cost of production are considered. Of such fibres may be mentioned the
_Mitsumata_ and _Kodzu_, easy of cultivation and giving a good yield
of material per acre of ground. The waxed papers used for stencils in
duplicating work on the typewriter are made from these fibres. The
_paper Mulberry_ is also a well-known fibre; while a third species
particularly valuable for thin papers is the _Gampi_.

(11) _Antaimoto Fibre._--The bark of this shrub is utilised in
Madagascar in very small quantities for local purposes and possesses
little interest for paper-makers.

(12) _Refuse Hempstalk._--The suggestion of the use of this material
comes from Italy, the hempstalk having been experimented with at San
Cesario Mill. This also is a fibre of a local interest only. The
percentage of cellulose is very high, being over 50 per cent.

(13) _Papyrus._--The revival of this celebrated material is of
comparatively recent date. It should be noted that the manufacture
of papyrus as carried out by the Egyptians, by smoothing out layers
of bark in order to utilise them as sheets of paper, and the present
day proposals which involve the production of paper pulp from papyrus,
are two entirely different propositions, and the success of the old
Egyptian method cannot be referred to as any assurance of success
for the production of paper from papyrus along modern lines. The
exploitation of this fibre must follow the lines of modern research
and commercial investigation, and its value, if any, could then be
established.

(14) _Pousolsia._--This is a fibre of the same family as hemp and
ramie. The value of this material is at present unknown, but the
ultimate fibre appears to possess a most extraordinary length. Very
little information is available at present as to its value for
paper-making.

(15) _Bamboo._--This material has been before the paper trade for many
years, having first been exploited seriously by Mr. Thomas Routledge in
1875. Since that date a good deal of work has been done in connection
with the fibre, but not until recently has the investigation been made
of a sufficiently extensive character to enable paper-makers to form
some conclusions as to the best methods of obtaining a reliable paper
pulp. The researches of the writer in India go to prove that with any
fibre it is necessary to take into account all the factors likely to
affect the final cost of the paper pulp delivered to any given paper
mill.

The figures given in a report recently published, "The Manufacture
of Paper and Paper Pulp in Burma," show the necessity of thorough
investigation into all the points likely to affect the final results,
viz., the price at which the paper pulp can be sold in England,
assuming that the fibre in question is suitable for the manufacture of
paper.

       *       *       *       *       *

_Examination of Fibres._--The exact chemical analysis of a new fibre
is necessary in order to establish completely its value for textile and
paper-making purposes, but the investigation of the suitability of the
fibre for paper-making may be simplified by simple reduction of the raw
material with caustic soda. The following process is sufficient for all
practical purposes:--

_Condition of Sample._--A record should be made of the general
appearance of the sample, its condition and the amount available for
the investigation. Any information available as to the source of supply
and the growth of the plant should also be noted.

_Preparation of Sample._--The material is cut up into small pieces. The
most convenient appliance for this purpose is a mitre cutter as used by
picture-frame makers. If the sample is a piece of wood, sections one
inch thick cut across the grain of the wood are most suitable, as they
can be readily cut up into thin flakes by this machine.

_Moisture in Sample._--A small average sample should be dried at 100°
C. for the determination of moisture.

_Treatment with Caustic Soda._--About two hundred grams of the raw
material is closely packed into a small digester or autoclave and
covered with a solution of caustic soda having a specific gravity of
1·050. A perforated lead disc should be placed above the sample in the
digester to prevent any of it from floating above the level of the
solution. The material should be digested for five or six hours at a
pressure of 50 lbs. The conditions of treatment here given will need to
be varied according to the nature of the fibre. Some materials can be
readily converted into pulp with weaker liquor and at a lower pressure,
while others will require prolonged treatment. These conditions must be
varied according to judgment or according to the effects produced by
the conditions already set out.

_Unbleached Pulp._--The contents of the digester are emptied out into
an ordinary circular sieve provided with a fine copper wire bottom,
having a mesh of about sixteen to the inch. The sieve is immersed in
water and the contents partially washed with hot water. The partially
washed material is squeezed out by hand and tied up in a strong cloth
and then kneaded thoroughly by hand in a basin of water which is
repeatedly renewed until the fibre is thoroughly washed. The process of
kneading at the same time reduces the fibre to the condition of pulp.
The water is carefully squeezed out of the pulp by hand, and the moist
pulp is then divided into two equal parts, the first of which is made
up into sheets of any convenient size, care being taken that none of
the fibre is lost. These sheets are then dried in the air and preserved
as samples of unbleached pulp, a record being made of the weight
produced.

_Bleached Pulp._--The second portion of the moist pulp is mixed with
a solution of bleach, the strength of which has been accurately
determined by the usual methods. The amount of bleach added should
be about 20 per cent. of the weight of air-dry fibre present in the
moist sample of pulp. The pulp should be bleached at a temperature
not exceeding 38° C., and when the colour has reached a maximum the
amount of bleach remaining in solution is ascertained by titration with
standard arsenic solution. In this way the amount of bleaching powder
required to bleach the pulp is determined. The product is then made up
into sheets of pulp which are dried by exposure to air and subsequently
weighed.

_Yield of Pulp._--The percentage yield of finished pulp obtained from
the raw material is determined from the figures arrived at in the
experiment described, and the weight of raw material necessary to
produce one ton of bleached pulp is readily calculated.

_Examination of Bleached Fibre._--The fibre should be carefully
examined under the microscope and a record made of general microscopic
features, especially with reference to the length and diameter of the
fibres, and the proportion of cellular matter present, if any.

_Sample of Paper._--It is only in the case of short-fibred material
similar to esparto and straw that sheets of paper capable of giving
comparative results as to strength can be made. The figures obtained
with fibrous materials of this kind are only comparative, because it is
possible in practice to make a much stronger sheet of paper when the
material is beaten properly under normal conditions.

A similar investigation should be made by submitting the fibre to
treatment with bisulphite of lime, that is to say, if the fibre lends
itself to such a process. A lead-lined digester is necessary, and the
solution employed is bisulphite of lime prepared according to the
directions given on page 160.

The preparation of sulphite pulp requires more attention than the
manufacture of soda pulp. It is most important that the digester
should be absolutely tight in order to prevent the escape of any free
sulphurous acid gas, and the contents of the digester must be heated
slowly until the maximum pressure has been reached.




CHAPTER III

THE MANUFACTURE OF PAPER FROM RAGS


[Illustration: FIG. 6.--A Rag Sorting House.]

The word rag is used to designate a very wide range of raw material
suitable for conversion into paper. In the case of high-class hand-made
writing papers only the best qualities are employed, such as new linen
and cotton cuttings from factories, or well-sorted rags of domestic
origin. The usual classification adopted by merchants who supply the
paper mills is somewhat as follows:--

    New white linen cuttings (from textile factories).
    New white cotton cuttings (from textile factories).
    Fine whites (domestic rags).
    Outshots (a quality between fines and seconds).
    Seconds (a grade inferior to fines).
    Thirds (inferior and dirty well-worn rags).
    Coloured prints (of all grades and colours).
    Fustians and canvas.
    Manila and hemp rope.
    Baggy, gunny, and jute.

The total amount of rag used in England for paper-making is not known.
The only figures available refer to rags _imported_; and these cannot
be regarded as a measure of consumption, which could only be arrived at
by first ascertaining the quantity of _home rags_ used. The imports of
rag at stated periods are given in the appended table:--

RAGS IMPORTED INTO ENGLAND.

  --------------+----------+----------+----------+----------+----------
        --      |   1872.  |   1882.  |   1892.  |   1902.  |   1905.
  --------------+----------+----------+----------+----------+----------
  Weight (tons) |  22,254  |  21,200  |  23,032  |  18,692  |  23,681
                |          |          |          |          |
  Value         | £373,035 | £303,349 | £214,065 | £173,732 | £224,232
  --------------+----------+----------+----------+----------+----------

_Sorting and Cutting._--All rags on arrival at the mill are carefully
sorted. This process is conducted entirely by women, who sort and cut
up the rags at special tables provided with cutting knives curved in
shape similar to a scythe. These are fixed at an angle in the centre
of the table, with the back towards and in front of each work-woman.
The top of the table is made of thick coarse wire so that some of the
dirt and foreign impurities may fall through. All buttons, hooks and
eyes, pins, leather, pieces of rubber, and other articles are carefully
removed, while seams and hems are also opened out. The rags are cut
into slips 3-5 inches long and then recut crosswise, and thrown into
suitable baskets or receptacles standing round the table, by which
means the _sorting_ operation is effectually carried out. The care and
attention given to the sorting is an important item in the manufacture
of papers of uniform quality, and in the best mills the sorting is
carried out to such an extent that twenty or twenty-five grades are
obtained.

[Illustration: FIG. 7.--A Rag Duster.]

_Dusting._--The rags are next passed through a machine which removes
dirt. This is a hollow cylindrical or conical drum having an external
covering of coarse wire cloth, which rotates inside a wooden box.
The shaft is provided with projecting spikes, so that the rags are
violently agitated in their passage through the machine. The dirt and
other impurities fall through the wire on to the floor of the room,
while the clean rags are discharged from the lower end of the drum. The
loss in weight varies according to the condition of the rags. With good
materials the loss may only be 1-2 per cent., while with dirty common
rags the loss during cleaning and dusting may amount to 10 per cent.

[Illustration: FIG. 8.--A Rag Cutter.]

_Boiling._--The further purification of the rags is effected by a
chemical treatment, viz., boiling at a high temperature with alkaline
substances, which process removes fatty, glutinous, and starchy matter
from the material.

[Illustration: FIG. 9.--Interior of Paper Mill for Hand-made Paper (R.
Batchelor & Sons).]

For this purpose a spherical digester is used, generally 7-9 feet
diameter, and capable of holding 2-2½ tons of rag. The boiler or
digester is filled with dusted rags, and the requisite amount of
alkaline solution added. The manhole is then closed, and steam admitted
through the hollow trunnions until the pressure reaches 20 or 30 lbs.,
at which pressure the boiling is continued for three to six hours
according to requirements, the digester rotating slowly the whole time
in order that the rags may be evenly and thoroughly boiled.

[Illustration: FIG. 10.--View of a Rag Boiler, showing connections.]

The liquor employed for boiling is a solution of caustic soda,
carbonate of soda, or milk of lime. In the case of caustic soda the
amount required varies from 5 to 10 per cent. of the weight of rag.
Caustic soda is preferable to lime, because it acts upon the grease
and other fatty matters, forming a soluble compound which is freely
removed in the subsequent process of washing. Many paper-makers,
however, use milk of lime, carefully strained through fine cloth,
almost exclusively. Considerable experience and skill are necessary
in this operation in order to avoid injury to the fibre not only as
regards its strength, but also its colour.

_Washing._--When the rags have been sufficiently boiled, the steam
is turned off and the pressure allowed to fall. This can be effected
quickly by blowing off from a valve fixed at the bottom of the boiler
opposite to the manhole. The cover is removed from the boiler and the
boiler slowly rotated in order that the contents may be discharged
into a tank placed below. The "black liquor," as it is called, is
then drained away from the rags, which are immediately subjected to a
preliminary washing. The process of washing must be carried out in a
thorough manner in order to remove all soluble compounds, which if left
would cause an unnecessary waste of bleach in the subsequent stages of
purification. There are many schemes employed for washing, most of them
being devised with the idea of using a minimum quantity of water.

The most general practice, in the absence of special machinery, is the
preliminary treatment in the tank below the digester, followed by a
more complete washing process in a machine known as a breaking engine.

This apparatus is a shallow oval-shaped vessel with circular ends,
divided lengthwise by a partition called a mid-feather, which, however,
does not extend the full length of the apparatus. In one of the two
channels into which the vessel is thus divided a heavy roll is fitted,
which is provided with a number of steel knives. On the floor of this
channel there is fixed a "bed-plate," also provided with projecting
knives which are parallel with the knives in the roll. The distance
between the knives in the roll and those in the "bed-plate" may be
altered as required by means of an adjusting screw. In the other
channel of the breaking engine there is fitted a "drum-washer," which
serves for the removal of the dirty water from the machine. This drum
is divided into sections by means of partitions which reach from the
centre to the circumference. The surface of the "drum-washer" consists
of a fine brass wire cloth supported by a coarser material placed
underneath.

[Illustration: FIG. 11.--A Breaking and Washing Engine.]

The breaking engine is half filled with clean water, and the rags are
thrown into the engine until it is suitably filled. The rotation of the
heavy roll causes the mixture of rags and water to circulate round the
vessel, the floor of which is so constructed that the pulp is drawn
between the roll and "bed-plate" and discharged over the "backfall,"
which is that portion of the sloping floor behind the "bed-plate."

The "drum-washer" rotates with its surface in contact with the mixture
in the engine, so that the dirty water passes through the wire cloth
and is caught in the curved sections or buckets inside the drum and
discharged into a trough adjacent to the centre, and thereby conveyed
away from the engine. Clean water is allowed to run into the vessel
at one end while the dirty water is discharged by means of the
"drum-washer." At the same time the rags are broken up by means of the
knives on the roll, so that when the rags are sufficiently washed, a
process which usually occupies four hours, they are also partially
disintegrated.

_Bleaching._--The clean disintegrated rag is next bleached by means of
ordinary bleaching powder solution. Bleaching powder is a substance
prepared by the action of chlorine gas on dry slaked lime, resulting
in the formation of a compound which has the property of bleaching or
"whitening" vegetable matters. The clear solution obtained by treating
the powder with water is utilised by the paper-maker for bleaching the
rag pulp.

Various methods are used for this purpose. Sometimes the requisite
volume of clear bleach liquor is added to the pulp in the breaker,
and the material kept in constant circulation until the operation
has been completed. In other cases the broken pulp is transferred to
a "potcher," which is a vessel similar in shape to the breaker, but
merely provided with paddles for keeping the pulp in circulation, and
bleached by the addition of chloride of lime solution.

Another method frequently adopted is to discharge the pulp from the
breaker, immediately after the addition of the bleach, into brick or
cement tanks, allowing the bleaching action to proceed spontaneously
without prolonged agitation.

In some instances the process is hastened by adding dilute sulphuric
acid to the pulp after the bleach liquor has been run in, or by
heating the mixture with steam. For high-class papers such devices as
this are seldom resorted to, as experience shows that the colour of
pulp bleached by drastic methods does not maintain a high standard.

The pulp is then thoroughly washed in order to remove every trace
of residual bleach, and also the soluble compounds which have been
formed during the operation. Very large quantities of water, clear
and free from suspended dirt, are necessary. In some mills any excess
of bleach is neutralised by the use of an "antichlor" such as sodium
hyposulphite, or sodium sulphite, but the best results are undoubtedly
obtained when the quantity of chemicals used is kept at a minimum.

If the pulp is bleached in a breaker or potcher, the washing is
effected by the aid of the drum-washer. With pulp treated in steeping
tanks, fresh water is allowed to percolate or drain slowly through the
mass.


ELECTROLYTIC BLEACHING.

The substitution of a sodium hypochlorite solution for the ordinary
calcium hypochlorite solution obtained from common bleaching powder has
been the aim of specialists for many years. As early as 1851 a patent
was taken out by Charles Watt for decomposing chlorides of the alkali
metals and the formation of hypochlorites. It was not until 1886 that a
practical method was devised for producing an electrolysed solution of
salt, but in that year Hermite introduced a continuous process in which
an electrolysed solution having a strength of three grammes chlorine
per litre was passed continuously into the potcher.

Many patents for the electrolysis of salt have been taken out during
the last twenty years, of which the Bird-Hargreave process is in
operation in England, the Rhodin process in America, the Siemens and
Halske in Norway, and the Oettel and Haas apparatus in Germany. The
figures relating to the latter apparatus may be mentioned as typical of
the present condition of electrolytic bleaching. The apparatus consists
of a narrow rectangular trough divided into a number of chambers
through which a solution of brine flows at a constant and steady
rate. The electric current is passed through the solution by suitable
electrodes, the temperature being kept down by means of a cooling coil.
The cost of producing the bleach liquor as given by the inventors of
the apparatus from the results of actual working are shown in the
following table:--

TABLE GIVING ANALYSIS OF COST FOR PRODUCING BLEACH LIQUOR.

  Capacity of tank              750 litres = 166 gallons.
  Strength or density of brine  1·5 Baumé, or 23 Twaddell.
        286 lbs. of common salt required for 166 gallons.

  --------------------+-------+-------+------+-------+--------+--------
  Hours worked        |   2   |   4   |   6  |   8   |   10   |    12
  Grammes of chlorine |       |       |      |       |        |
    per litre produced|  4·35 |  7·38 |  9·9 | 12·42 |  14·31 |  16·20
  Temperature C. of   |       |       |      |       |        |
    brine during      |       |       |      |       |        |
    operation         |   20  |   21  |  20  |   21  |   20   |    20
  Ampères of 110 volts|   55  |   50  |  46  |   52  |   47   |    43
  Power in h.p. hours |   16  |   31  |  45  |   61  |   75   |    89
  Cost of the h.p. at |       |       |      |       |        |
    ·22_d._ per h.p.  |       |       |      |1_s._  |1_s._   |1_s._
    hour              | 3½_d._| 6¾_d._|10_d._| 1½_d._|  4½_d._| 7½_d._
  Cost of salt        |1_s._  |1_s._  |1_s._ |1_s._  |1_s._   |1_s._
                      |  6_d._|  6_d._| 6_d._| 6_d._ |  6_d._ |  6_d._
  Total cost          |1_s._  |2_s._  |2_s._ |2_s._  |2_s._   |3_s._
                      | 9½_d._| 0¾_d._| 4_d._| 7½_d._| 10½_d._| 1½_d._
  Total chlorine      |       |       |      |       |        |
    obtained in kilos.| 3·262 | 5·535 | 7·425| 9·315 | 10·732 | 12·150
  Cost of chlorine per|       |       |      |       |        |
    kilo.             |6·6_d._| 4½_d._|3¾_d._|3·4_d._| 3·2_d._|  3_d._
  Salt used per kilo. |       |       |      |       |        |
    chlorine          |   35  |   20  |  15  |   12  |   10   |    9
  --------------------+-------+-------+------+-------+--------+--------

The above costs have been estimated on prices as follows:--

                    Coal  10_s._ per ton.
                    Salt  12_s._ per ton.

After 12 hours the 166 gallons (750 litres) are converted into
electrolytic bleach liquor containing 26¾ lbs. of active chlorine
(12·15 kilos.).

_Beating._--Although the rags are reduced by the breaking engine to a
condition of fibrous lint, called "half-stuff," they are not fit for
conversion into paper. They have to be _beaten_ in special machinery
until a complete separation of the single fibres has been effected,
and this process is rightly regarded by many paper-makers as the most
important stage of manufacture.

[Illustration: FIG. 12.--Oettel and Haas' Apparatus for the manufacture
of Electrolytic Bleach Liquor.]

The beating engine is similar in construction to the breaking engine,
but there are certain essential differences in arrangement and
manipulation. There is usually no drum-washer; the roll contains a
large number of knives which are fixed in clumps or sets of three
round the circumference; the lowering of the roll upon the bed-plate
is carefully watched and controlled, and the desired effects are only
obtained by strict attention to the condition of the pulp during the
whole process.

[Illustration: FIG. 13.--The "Hollander" Beating Engine.]

The beater is first partially filled with water, and the drained
half-stuff added gradually until the "furnish," a convenient term
applied to the contents of the engine, has the proper consistency,
which varies according to the nature and quality of paper required.

The mass is circulated steadily round the engine by the action of the
beater roll, which is lowered from time to time until the distance
between the knives on the roll and those on the bed-plate has been set
to the desired adjustment. This lowering of the roll and its proper
adjustment call for the greatest care.

_Influence of the Beating._--The importance of this operation can
easily be judged from one or two specific examples. In the case of rag
papers the two extremes of variation are represented by the ordinary
blotting paper on the one hand and a hard strong writing paper known
as a _loan_ on the other. Now the great difference in these papers may
be traced to the careful selection of the rag and the treatment in the
beater as the two primary causes of the final results.

For blotting papers it is essential that the rags should be old and
tender. In the beating operation subsequent to the usual boiling and
bleaching processes the half-stuff is beaten quickly with sharp knives,
the roll being lowered soon after the engine is filled, so that the
beating is finished in about one to one and a half hours.

For the strong writing paper new strong rags are selected. In the
beating process the knives used are dull, the roll is lowered slowly
and cautiously, and the beating goes on for eight to ten hours.

The effect of such difference in treatment is easily seen by
examination of the fibres of the papers under the microscope. In
the first case the fibres appear short with clean cut ends, the
shape little distorted, the structure well defined, bearing a strong
resemblance to the unbeaten material. In the case of the well-beaten
paper the ends of the individual fibres appear to be drawn or frayed
out, the fibres do not possess the sharp well-defined outline
characteristic of blotting paper; they are partly split up into
fibrillæ which lie together in a confused mass.

In the _blotting_ paper these effects are produced because the knives
being sharp cut up the material quickly, and in the _writing_ paper
because the dull "tackle" tends to draw out the fibres and tear them up
lengthwise.

The practical result is a spongy, soft, and bulky blotting and a hard,
strong, heavy writing paper. Of course the great difference between a
blotting and a writing paper is not all due to this one operation,
but is obtained by a series of operations, of which one of the most
important is, however, the beating.

_Colouring the Paper._--The pulp is brought to any desired tint by
the addition of mineral pigments or aniline dyes to the contents of
the engine. The latter soluble dyes, however, are seldom used for
high-class rag papers. Prussian blue, ultramarine, and smalts are
chiefly used for this purpose, giving toned blue, azure, and blue laid
papers.

[Illustration: FIG. 14.--The Hand Mould showing Frame and Deckle.]

_Making the Paper._--The beaten pulp, when duly prepared, is run from
the engine into store tanks known as stuff chests, ready for the
actual manufacture. The pulp properly diluted with water is strained
through special screens to remove any insufficiently beaten material
and any impurities present, after which it is run off into the vat, a
square-shaped vessel built of wood or stone.

The apparatus used in forming the sheets is called a _hand mould_.
The mould is a rectangular frame of mahogany upon which is stretched
tightly a fine wire cloth, the surface of the latter being kept flat
by a coarser wire cloth fixed underneath, supplemented by wedge-shaped
pieces of wood. A second frame called the _deckle_ fits on to the mould
in such a manner as to form a shallow tray, the bottom of which is the
fine wire cloth.

The vatman takes up the mould with both hands and dips it into the
vat full of pulp in a slanting position, drawing it through the stuff
towards him in a peculiar manner and lifting it out from the vat with
a definite quantity of the mixture in the frame. As the water drains
away from the pulp, through the wire cloth, he imparts a shaking motion
to the mould in order to cause the fibres to "felt" properly, this
felting or interlacing of the fibres being an essential feature in the
manufacture of a good sheet of paper. When the water has drained away
sufficiently from the pulp, the vatman removes the deckle from the
mould and passes the latter over to the coucher, who takes the mould,
reverses it, and presses the contents, which may now be described as a
wet sheet of paper, down on to a damp piece of felt, by which means the
paper is transferred to the felt. He returns the mould to the vatman,
who meanwhile has made another sheet with a duplicate mould, and then,
having laid a second felt upon the wet sheet of paper, he proceeds to
transfer the next sheet of paper to the second felt. This process is
continued until a pile is formed consisting of wet sheets of paper
alternated with pieces of felt.

The pile is at once submitted to great pressure in the hydraulic press,
and the excess water slowly forced out, while at the same time the
sheets are compressed and thus "closed up," as it is termed. When all
the excess water has been removed as far as possible, the pile is taken
away and the sheets of damp paper taken out, the felts being placed in
one pile ready for further use, and the sheets of paper in a second
ready for the next process.

The papers are put back into the press without felts between the sheets
and left for some time. In most cases the sheets are turned round or
mixed in with the sheets of another pile, before pressing. In this way
any unevenness or irregularity in the sheets is counteracted and a more
uniform result obtained.

When these changes are repeated several times the paper acquires an
even texture and becomes firm and hard.

_Drying the Paper._--The sheets are hung up in the _loft_, as the
drying room is called, upon poles or ropes. The moisture gradually
evaporates, and the paper is thus dried by exposure to air. In winter
it is necessary to warm the air in the loft, as the air is then
saturated with moisture. In lofts of limited capacity the air is heated
in order to hasten the process, but the best paper is allowed to dry
naturally, as by this means the shrinkage is gradual and a maximum
strength is attained.

[Illustration: FIG. 15.--Apparatus for Sizing Paper in continuous
Rolls.]

_Sizing the Paper._--The dried paper as it leaves the loft is termed
_Waterleaf_ because, being unsized, it readily absorbs water, and
therefore before it can be used it must be sized. For this purpose
it is dipped into a solution of gelatine, an operation described as
_tub-sizing_ or _animal-sizing_, the former term being used on account
of the tub in which the size is kept, and the latter on account of
the fact that the gelatine is made from animal matter such as hides,
cartilage, hoofs, and other refuse.

_Animal Size._--This is prepared from hide pieces, skins, and the
like by a simple process, which, however, requires a good deal of care
in order to obtain the best results. The material is first thoroughly
washed in plenty of clean water, and then heated with a definite
quantity of water in a steam jacketed copper pan. The pieces slowly
dissolve until a solution of gelatine is produced, and after the dirt
and impurities have settled to the bottom of the pan the clear liquid
is drawn off into store vessels. There are many details of a technical
character to be attended to in the manufacture of good gelatine, and as
the process is expensive, considerable attention is demanded at this
stage in the completion of a sheet of paper.

The dry sheets of paper are sized by the simple expedient of dipping,
or by the passage of the paper through a long trough. In the first
case the workman takes up a number of sheets and dips the bunch into a
vat of size at the proper temperature, about 100° Fahrenheit. He then
allows the surplus size to drain off, and the sheets are submitted to a
slight pressure in order to remove the excess of gelatine that will not
drain off.

In the second case a different method is adopted in that the sheets
of paper are carried by travelling felts through a bath of heated
size, the excess gelatine being removed by the action of rubber or
wooden rollers through which the papers are passed before leaving the
apparatus. The papers are quickly and evenly sized by this method,
which is now most generally used.

_Glazing._--When the sheets of paper are quite dry they are ready for
glazing, a process which turns the dull rough surface of the sized
sheet into a highly polished smooth surface fit for use. The sheets are
placed singly between copper or zinc plates, and a pile of these passed
several times through heavy iron rollers, great pressure being applied
to the latter during the operation.

[Illustration: FIG. 16.--A Supercalender.]

The amount of polish imparted by this plate-glazing process, as it
is termed, can be varied considerably. With a light pressure and
few rollings, the sheet of paper can be turned out having a fairly
smooth surface, and without a conspicuously shiny appearance. By
employing a great pressure and repeated rolling a much higher surface
is attainable. If the plates are hot a still higher finish is
possible. Machine-made rag papers are glazed usually by means of the
supercalender, which is a stack of alternate steel and paper rolls
placed one above the other in a vertical position. The reel of paper
passes between these rolls and becomes highly surfaced.

This operation effects many changes in the paper, besides imparting
a good finish. The thickness of the sheet is reduced by about 40 per
cent., the fibres being compressed much closer together. The tensile
strength of the paper is also materially increased, and in every
way the paper is improved. Moderation is essential in this as in
everything, because excess of glazing weakens a paper, rendering it
brittle and liable to crack when folded.

_Laid and Wove Papers._--When certain papers are held up to the light
and carefully examined it will be noticed that they appear to contain
delicate transparent lines running parallel with one another at equal
distances of about an inch, and that these are intersected by similar
transparent lines running at right angles, which are much closer
together. Such papers are known as _Laid_ Papers, and the peculiar
formation of the transparent lines is due to the construction of the
mould used in the making. The wire surface of this mould consists of a
number of somewhat stout wires placed about one inch apart, interwoven
with finer wires running across and at right angles, which are threaded
much closer together. When the mould is dipped into the vat and
withdrawn, the water drains away from the under surface of the wire,
and the moist pulp settles down on the upper surface; but since the
coarser wires project a little from the finer threads, the paper is
slightly thinner along those wires, though to an almost infinitesimal
extent, with the result that on drying the sheet appears to contain
transparent lines.

_Wove_ papers are so called from the nature of the mould used. The
surface of the mould in this case consists of fine wires equally
distributed, being woven in such a manner that the wires are
equidistant from one another, as in ordinary wire gauze. A wove
paper, on being examined in the light, simply shows a number of small
diamond-shaped spaces, which in the majority of instances are difficult
to detect.

_The Watermark._--The transparent device observed in many papers when
held up to the light is known as the watermark, a term probably derived
from the conditions existing at the time the sheet of paper is made on
the mould. The effect is produced by means of a raised design sewn or
soldered to the surface of the mould, the design being fashioned out of
fine wire.

[Illustration: FIG. 17.--The First Watermark in Paper.]

When a mould thus fitted with the design is dipped into a vat of pulp
and lifted out, the water falls through the wire, and the pulp sinks
down on to the surface of the mould, forming a replica, so to speak,
of the design, which is easily seen when the dry paper is held up to
the light, because the paper is thinner just at those points where the
wires forming the design come into contact with the wet pulp.

Some of the watermarks are very elaborate and interesting. A familiar
illustration of a beautiful design of this description is to be found
in the Bank of England notes. As a general rule the ordinary watermark
consists of a mere trade term such as "Vellum," "Zenobia," or of the
name of the manufacturer, such as "J. Whatman," "R. Batchelor," and
so on. In the earlier days of paper-making many highly interesting
designs were used, and some of these are still extant. In fact many of
the names by which certain standard sizes of paper are known owe their
origin to the watermarks employed.

The earliest known watermark bears the date A.D. 1301, being in the
form of a globe and cross, as shown. Of equal interest are those
designs from which certain papers are called foolscap, crown, pott,
post, royal, columbier, and so on. The watermarks are now little used,
but the terms are still retained, as indicating the size of the sheet.


MICROSCOPIC FEATURES OF COTTON AND LINEN FIBRES.

The _cotton_ fibre is about 30 mm. long, with an average diameter of
·025 mm. of tube-like shape, and having a prominent central canal.
There are no cross markings on the cell walls, and the ends of the
fibre are rounded off into a somewhat blunt point. It exhibits a marked
tendency to twist itself, especially if dry, and this peculiarity is
readily observed with the raw material.

The process of paper-making alters the characteristic structure of the
fibre very greatly. The ends of the fibre are seldom to be seen; the
curious twist is less prominent, and the fibres are torn and destroyed.
The effect of the beating process, for example, on cotton is easily
to be noticed by comparing the fibres of a blotting paper under the
microscope with the fibres of a _bank_ or _loan_ paper.

The distortions produced by prolonged beating renders the
determination of the exact percentage of cotton in a rag paper rather
difficult, but the features to be looked for are the absence of pores,
cross markings, the existence of a central canal, striations produced
in many cases on the cell walls parallel to the length of the fibre.
The structural features are more readily observed when the fibres are
stained with a suitable reagent. (See page 71.)

[Illustration: FIG. 18.--Cotton.]

The _linen_ fibre has an average length of 27 mm. with a diameter of
·02 mm. The raw flax is very different from raw cotton and is easily
distinguished. The fibre is slender in shape, having thickened knots
at regular intervals throughout its length, the general appearance of
which may be compared to a stick of bamboo. The central canal of the
fibre is extremely narrow, running like a small thread through the
length of the fibre. The cell walls are further marked by numerous
pores, which appear as small dark lines running from side to side, but
not meeting in the centre.

[Illustration: FIG. 19.--Linen.]

In the treatment necessary for making paper these characteristics are
largely destroyed, and while it is quite easy to ascertain that a paper
is of linen, or of cotton, or that a paper is mainly cotton with a
small percentage of linen, yet there are conditions under which it is
difficult to determine the exact percentage of cotton or linen in a
rag paper. If, for example, a paper contains nearly equal quantities
of cotton and linen, the exact proportions cannot be determined closer
than 10 per cent., especially in well-beaten papers.


REAGENT FOR STAINING FIBRES.

_Preparation._--Dissolve 2·1 grams potassium iodide and 0·1 grams
iodine in 5 c.c. of water. Mix this solution with a solution containing
20 grams of dry zinc chloride in 10 c.c. of water. Allow the mixture to
stand; pour off the clear liquid into suitable bottles.


COLORATION PRODUCED.

  Cotton, linen, hemp.--Wine red.
  Esparto, straw and wood cellulose.--Bluish violet.
  Mechanical wood, unbleached jute.--Yellow.
  Manila hemp.--Blue, bluish grey to yellow.




CHAPTER IV

ESPARTO AND STRAW


ESPARTO PAPERS.

The value of Esparto for the manufacture of high-class printing and
medium quality writing paper is well known. This material has qualities
which cannot readily be obtained from other fibres, such as rag and
wood pulp. It is chiefly used in papers required for lithographic
printing, books, and art illustration, since it gives a sheet having a
good surface and one which is soft and flexible.

The grass is obtained from Spain, Morocco, Algeria, Tunis, and Tripoli,
in which countries it grows wild, requiring very little cultivation.
The condition of the crop is improved by proper treatment, and in
districts where the grass is cut for export as a paper-making material
attention is given to cultivation.

The plant grows to a height of three or four feet, and when mature the
long blades of grass curl up into the form of a cylinder resembling a
piece of wire. The leaf consists of two parts, the stalk and a sheath,
which are easily separated when harvested. The grass is pulled up by
hand and stacked into heaps in order that it may be dried by the heat
of the sun, after which process it is carefully picked over for the
removal of all extraneous matter and impurities. It is then graded,
the best sorts being kept for weaving, and the remainder being sold
for paper-making. It is packed up into large bales of about 4 cwt.
capacity, compressed into small bulk by powerful presses, and shipped
to England.

_Esparto Pulp._--The first process in the manufacture of the paper
is cleaning. The bundles of grass are opened up, shaken out, and put
through a willowing machine. This consists of a hollow conical drum,
the outer surface of which is a coarse wire cloth. Inside the drum is
fitted a shaft provided with wooden teeth, and as the grass passes
through it is tossed about and the dust removed. The clean grass is
conveyed by travelling belts to the digester house. For the production
of a high-class paper the grass is often examined by girls, who stand
on either side of the travelling conveyer and take out any coarse root
ends and foreign material not removed by the willowing machine.

_Boiling._--The object of submitting esparto to chemical treatment is
to obtain a pure paper-making fibre known as cellulose. The composition
of this raw material is shown by the following analysis:--

_Spanish Esparto._

      Cellulose                          48·25
      Water                               9·38
      Aqueous extract                    10·19
      Pectous matter                     26·39
      Fatty matter                        2·07
      Ash                                 3·72
                                        ------
                                        100·0
                                        ------

      Yield of dry cellulose obtained in actual practice
        from good raw material 45 to 48%

By boiling the esparto with caustic soda under pressure for a stated
time, the non-fibrous constituents are removed, leaving the cellulose
in a more or less pure form according to the severity of the chemical
treatment.

[Illustration: FIG. 20.--An Esparto Duster.]

In practice the grass is packed tightly into upright stationary
digesters and a definite quantity of caustic soda solution added,
the amount of chemical used being equal to 15-18 per cent. of the
weight of grass packed into the digester. The form of digester almost
universally employed is that known as the Sinclair's "vomiting" boiler,
which is constructed so that a continuous circulation of the liquid
is maintained by means of what are called "vomit" pipes. These are
fitted to the sides of the digester in such a manner that the caustic
soda solution circulates from the bottom of the digester, up through
the "vomit" pipes, and is discharged downwards upon the contents of
the boiler through a perforated plate fixed in the upper part of the
digester. The requisite quantity of caustic soda solution is placed in
the digester, and steam admitted into the bottom of the vessel while
the grass is being thrown in. In this way a much larger weight of grass
can be boiled at one operation, since the bulk is greatly reduced when
the grass has become thoroughly soft and wet.

[Illustration: FIG. 21.--Sinclair's "Vomiting" Esparto Boiler.]

When the boiler is loaded the inlet is closed up and steam turned on
to the full pressure of about 40 or 50 lbs., this being maintained
for a period of about four hours. The non-fibrous constituents of the
esparto are gradually dissolved out by the caustic soda, and when the
operation is completed the black liquor is run off from the digester
into large store tanks, and the esparto grass which remains in the
digester is then completely washed until the soda is almost entirely
washed out.

[Illustration: FIG. 22.--A Porion Evaporator.]

The conditions for boiling and bleaching esparto are varied by the
paper-maker as circumstances require. A maximum yield of fibre is
obtained when the least possible quantity of caustic soda is used, but
a larger percentage of bleaching powder may be necessary to ensure a
well bleached pulp. The use of an excess of caustic soda is probably
the general practice for several reasons, amongst which may be noted
the advisability of guarding against irregularities in the quality
of the esparto, and consequent insufficient boiling, as well as the
advantage of having some free caustic in the spent liquors to prevent
the furring up of the tubes of the evaporating apparatus in the soda
recovery department.

The following experiments, given by a contributor to the _Paper Trade
Review_ some years ago, are interesting as showing the effect of
varying proportions of caustic soda used per unit of grass:--

EXPERIMENTS _RE_ YIELD OF AIR-DRY BLEACHED PULP FROM ORAN ESPARTO.

  Air-dry Pulp containing 10 per cent. water.

  ---+--------+----------------+------------------+-------+--------+-------
     |Esparto.|  Soda Liquor.  |   Conditions of  |       |  Dry   |
     |        |                |     Boiling.     |Weight | Pulp   |Bleach-
  ---+--------+-------+--------+------+-----+-----+  of   |on Dry  | ing
  No.|   Wt.  |Volume,|   Per  |Time. |Temp.|Pres-|Air-dry|Esparto.|Powder.
     | taken. | C.C.  |  cent. |Hours.|° C. |sure.|Pulp.  |  Per   |  Per
     | Grams. |       |Na_{2}O.|      |     | Lbs.|Grams. | cent.  | cent.
  ---+--------+-------+--------+------+-----+-----+-------+--------+-------
   1 |   200  |  800  |  1·58  |  3   | 142 |  55 | 87·30 |  43·65 |  29·5
   2 |   200  |  800  |  2·13  |  3   | 142 |  55 | 80·67 |  40·33 |  18·5
   3 |   200  |  800  |  2·69  |  3   | 142 |  55 | 72·00 |  36·00 |  10·5
  ---+--------+-------+--------+------+-----+-----+-------+--------+-------

  No. = No. of Experiment.

PRACTICAL DATA CALCULATED FROM EXPERIMENTS.

  ---+------------+----------+------------+-------------+----------------
     |   Boiling. |Weight of |60 per cent.| Bleaching   |For One Ton of
  No.+------+-----+Esparto to|Caustic Soda|  Powder     |Esparto used.
     |Time. |Pres-|give 1 ton|required to |required to  +----------------
     |Hours.|sure.|  Pulp.   |  Digest    |Bleach 1 ton | 60 per |Bleach-
     |      |Lbs. |  Cwts.   | Esparto.   |Air-dry Pulp.| cent.  |ing
     |      |     |          |  Cwts.     |   Cwts.     |Caustic.|Powder.
     |      |     |          |            |             |  Lbs.  | Lbs.
  ---+------+-----+----------+------------+-------------+--------+-------
   1 |   3  |  55 |   45·8   |     4·30   |     5·26    |   210  |   260
   2 |   3  |  55 |   49·5   |     6·27   |     3·39    |   282  |   156
   3 |   3  |  55 |   55·5   |     8·90   |     1·96    |   358  |    79
  ---+------+-----+----------+------------+-------------+--------+-------

  No. = No. of Experiment.

_Recovery of Spent Liquor._--As it is possible to recover 75 to 80 per
cent. of the soda originally used in digesting the esparto, the washing
of the boiled grass is conducted on scientific principles in order to
ensure a maximum recovery of soda at a minimum cost.

The recovery is effected by evaporating down the black liquor, together
with the washing waters, to a thick syrupy mass, which can be burnt.
The organic and resinous constituents of the esparto which have been
dissolved out by the caustic soda, forming the soluble soda compounds,
ignite readily, and during combustion the organic soda compounds are
converted more or less completely into crude carbonate of soda.

It is obvious, then, that the cost of recovery depends mainly on the
quantity of weak washing water which has to be evaporated. Consequently
methods are devised by means of which the grass is thoroughly washed
with as little water as possible, and some of the methods are very
ingenious.

The spent liquors and washing waters are evaporated to a small bulk in
a vacuum multiple effect apparatus, and the thick liquid mass obtained
by evaporation is burnt either in a rotary furnace or on an ordinary
hearth. Every precaution is taken to effect this operation with a
minimum quantity of coal. The burning off of this mass results in the
formation of a black substance which is taken away from the furnace
and allowed to char or slowly burn until the impure white soda ash, or
carbonate of soda, is obtained.

Two systems of recovery are in general use, which deserve a brief
notice:--

_Direct Evaporation._--The liquors may be evaporated to a small bulk
ready for incineration by treatment in long shallow pans or furnaces,
the heat necessary for the process being obtained mainly from the
combustion of the thick concentrated liquor. The most familiar type of
this form of apparatus is the Porion evaporator.

[Illustration: FIG. 23.--Scott's Multiple Effect Evaporator.]

The combustion of the concentrated liquor is started by a coal furnace
at one end of the apparatus. The thick viscous mass catches fire and
burns with a fierce flame, and the heat is utilised in evaporating the
weaker liquors which flow continuously through shallow brick troughs,
the surface of which is freely exposed to the heat and flames from the
hearth where the organic soda compounds produced in the boiling of
esparto are being incinerated and converted into soda ash.

Under suitable conditions this evaporator is most economical in its
results. It can be erected cheaply, and when all the heat is fully used
in every possible direction it can be worked at a low cost compared
with the more modern multiple effect evaporators.

_Vacuum Multiple Effect Evaporation._--Advantage is taken of the
fact that water boils at a lower temperature in a vacuum than at the
ordinary pressure of the atmosphere. There are many forms of apparatus
based on this principle, amongst which the most recent is Scott's
evaporator. The black liquor from the boilers is pumped through tubes
heated externally by high-pressure steam. The liquor is passed into a
chamber in which a slight vacuum is maintained, so that immediately on
entering, the liquor parts with a good deal of water in the shape of
steam. The steam liberated is utilised in producing further evaporation
of the partially concentrated liquor, and this operation is repeated
several times until the concentration is effected to the desired point.

In most cases the actual incineration of the thick liquor is carried
out in a rotary furnace when such an apparatus as this is used.

EVAPORATION TABLE.

Showing the volume of liquor obtained by evaporating 1,000 gallons of
weak black lye of density _d_ to a higher density D.

  -------------+-----------------------------------------------------
  Lower        |  Higher Density D (Twaddell) at 100° F.
  Density _d_  +-----------------------------------------------------
  (at 100° F.).| 20. | 25. | 30. | 35. | 40. | 45. | 50. | 55. | 60.
  -------------+-----+-----+-----+-----+-----+-----+-----+-----+-----
        2      |100  | 80  | 66·6| 57·1| 50  | 44·4| 40  | 36·3| 33·3
        3      |150  |120  |100  |85·7 | 75  | 66·6| 60  | 54·5| 50
        4      |200  |160  |133·3|114·3|100  | 88·8| 80  | 72·7| 66·6
        5      |250  |200  |166·6|143  |125  |111·0|100  | 90·9| 83·3
        6      |300  |240  |200  |171·4|150  |133·3|120  |109  |100
        7      |350  |280  |233·3|200  |175  |155·5|140  |127  |116·6
        8      |400  |320  |266·6|228·6|200  |177·6|160  |145·5|133·3
        9      |450  |360  |300  |257  |225  |200  |180  |163·5|150
       10      |500  |400  |333·3|286  |250  |222  |200  |181·8|166·6
  -------------+-----+-----+-----+-----+-----+-----+-----+-----+-----

  EXAMPLE:--1,000 gallons of weak liquor at a density of 7° Twaddell
      are reduced to a volume of 200 gallons having a density of 35°
      Twaddell, or to a volume of 140 gallons with a density of 50°
      Twaddell, by evaporation.

_Preparation of Caustic Soda._--The crude soda ash recovered from
previous boiling operations is dissolved in large lixiviating tanks
and extracted with hot water. The clear solution obtained after
all impurities have been allowed to settle is pumped up into the
causticising tanks, where it is converted into caustic soda, the loss
due to the amount of soda not recovered being made up by the addition
of ordinary soda ash. The causticising pans are large circular iron
vessels usually 9 feet diameter and 8 or 9 feet deep, into which a
known volume of the recovered carbonate of soda solution is placed.

A weighed quantity of ordinary quicklime is then put into a perforated
iron cage which is fixed inside the causticising pan at such a level
that the whole of the lime is immersed in the solution. The liquor is
kept in constant circulation by means of an agitator and heated to
boiling point, with the result that the chemical reaction sets in,
the carbonate of soda being converted into caustic soda and the lime
being thrown out as chalk. When the operation is completed, the steam
is turned off and the chalk allowed to settle. The clear liquor is
carefully strained off and pumped up into store tanks from which the
required quantities are drawn off into the digesters as circumstances
demand.

_Washing._--The grass which has been partially washed in the digester
is dug out by the workmen and discharged through a manhole fitted on
one side of the digester near the bottom. It is then conveyed in any
convenient manner to the breaking engine, in which the grass is more
completely washed. This important machine has already been described
on page 53. The floor of the vessel slopes slightly upward towards
the front of the roll and falls suddenly behind the roll, in order to
promote a circulation of the contents of the engine round and round the
vessel.

A definite weight of boiled grass is thrown into the engine together
with a large quantity of fresh water. The circulation of the roll draws
the mixture of pulp and water between the knives, breaking it up and
at the same time discharging it behind the beater roll, and producing
a continuous circulation of the mixture in the two sections of the
vessels.

The dirty water is continuously removed from the vessel by means of a
"drum-washer." This is a large hollow drum, the outer surface of which
consists of a fine wire cloth, the interior of the washer being fitted
with specially curved scoops. The drum-washer is lowered until it is
half immersed in the mixture of pulp and water, and as it rotates the
dirty water finds its way through the wire cloth, being caught up by
the internal scoops and discharged through a pipe to a drain outside
the breaking engine. At the same time fresh water is run into the
vessel at one end, and the continuous washing of the pulp thus effected.

_Bleaching._--The clean boiled grass is bleached by means of a solution
of chloride of lime.

There are several methods used for this purpose, each of which has
special advantages of its own, though this is largely a question of
local conditions:--

(A) The pulp can be bleached in the washing engine directly the grass
has been sufficiently cleaned. In this case the flow of fresh water
is stopped and as much water as possible removed by means of the
drum-washer. The drum-washer is then raised out of the pulp and a
known volume of bleaching powder solution corresponding to a definite
weight of dry powder is added to the contents of the breaking engine.
The amount used depends on the quantity of dry grass in the breaking
engine, the usual proportion being 8 to 10 per cent. on the calculated
air-dry weight of raw grass. As the stuff circulates round the engine
the colour gradually changes from dark yellow to white.

The process is sometimes hastened by blowing a small quantity of steam
into the mixture and thereby raising its temperature. Considerable care
must be exercised in using heat, because pulp bleached quickly by this
means is liable to lose colour at the later stages of manufacture.

When the pulp has been bleached to the required extent, the drum-washer
is again lowered into contact with the bleached pulp, and the latter
is thoroughly washed so as to be quite free from traces of bleach and
other soluble impurities.

(B) Esparto is often bleached in a "Tower" bleaching engine which
consists of a tall cylindrical vessel of 9 feet diameter, and 15 or 16
feet deep, at the bottom of which is fixed a small centrifugal pump.

The boiled grass together with sufficient water and clear bleaching
powder solution is placed in the engine; the centrifugal pump draws
the mixture from the bottom of the vessel and discharges it, by means
of a large external pipe, direct into the top of the vessel, where, as
it falls, it comes into contact with a circular baffle-plate, which
distributes the pulp evenly over the surface of the mixture in the
vessel. A continuous and rapid circulation is thus maintained, and the
process is said to be very effective. The bleached pulp is subsequently
washed free from any traces of bleach.

(C) Esparto is frequently bleached by the "steeping" process. In this
case the pulp is washed in the breaking engine, mixed with the required
quantity of bleach, and at once discharged through the outlet pipes
of the engine into large brick tanks, where the bleach is allowed to
act quietly upon the boiled grass. This method produces a pulp of good
colour and is economical.

Whichever process of bleaching is adopted, it is necessary to remove
all the by-products formed during the process, as these soluble
by-products if left in the mixture produce a lowering of colour.

The presence of small traces of bleaching powder solution can be
detected by the use of starch and potassium iodide test papers. If a
handful of the pulp after bleaching, when squeezed out, does not turn
the test paper violet or blue, then the absence of any free bleach is
taken for granted. The slightest trace of bleach will turn such test
papers blue or violet according to the amount present. This is the test
usually applied by the men in charge of the bleaching operations.

_Making Sheets of Esparto Pulp._--For convenience in handling, it is
usual to work up the washed and bleached pulp into the form of moist
sheets. This is effected on a machine known as a "presse-pâte," an
apparatus which closely resembles the wet end of a paper machine. It
consists of a set of flat strainers or screens, a horizontal wire
similar to the paper machine wire, provided with deckles, the usual
couch rolls, and press rolls.

[Illustration: FIG. 24.--A Presse-pâte for Esparto Pulp.]

The pulp diluted with water is passed through the screens and on to
the horizontal wire, where it is formed into a moist sheet, the water
draining away from the wire, and also being removed by vacuum pumps.
The thick sheet of pulp is carried through the couch rolls and press
rolls, being finally wound up on a wooden roller at the end of the
machine. In this moist condition it is ready for use in the mill.

_Dry Esparto Pulp._--When the bleached pulp is intended for export
a more elaborate machine is used--to all intents and purposes a
paper-making machine--by means of which the continuous sheet of moist
pulp is dried and cut up into smaller sheets of suitable size. These
dried sheets are packed up in bales containing 2 cwt. or 4 cwt. of
dried pulp, then wrapped in hessian and bound with iron wires.

_Other Methods._--Since the yield of esparto pulp from the raw material
is less than 50 per cent. and it requires 45 cwt. of grass to make
one ton of finished pulp, methods have been devised for treating the
grass in the green state in the districts where it is grown, but so far
nothing has been done on a large scale.

_The isolation of the cellulose by alkaline treatment in the cold_ has
been suggested, but the method never passed beyond the experimental
stage. This process was indeed first mentioned by Trabut, who many
years ago considered that the removal of non-fibrous constituents from
fresh grass could be readily accomplished by the less drastic treatment
of the esparto with alkaline carbonates of soda and potash at ordinary
temperatures.

_The production of esparto pulp by bacteriological fermentation_ is an
idea of later date. According to the inventor, the grass is crushed
mechanically by means of rollers and then immersed in sea water
inoculated with special bacillus obtained from esparto, and gradually
resolved into cellulose and soluble by-products by fermentation which
is complete in about eleven days. The commercial value of this idea has
not yet been demonstrated.


ESPARTO PULP: MICROSCOPICAL FEATURES.

The pulp of esparto when examined under the microscope is easily
recognised, first by the characteristic appearance of the long slender
cylindrical-shaped fibres, and secondly by the numerous cells always
present. These cells consist of cuticular vessels with serrated edges,
and also of small pear-shaped seed hairs, the shape of which is a ready
means of identifying esparto. An examination of the transverse section
of the raw material indicates the source of these pear-shaped vessels.

_Test for Esparto in Papers._--Paper containing esparto fibre may be
tested by means of a weak solution of aniline sulphate. The suspected
paper is gently heated in the test reagent, and if esparto is present
the paper turns a rose-red or pink colour, the depth of colour being
a measure of the amount of esparto. Most of the modern book papers
are prepared from chemical wood pulp and esparto mixed in varying
proportions, and while this test can be used as a means of detecting a
small or a large proportion of esparto, a microscopical examination is
required for a more accurate estimation.

The proportions used by the paper-maker depend upon the weighing
out of the wood pulp and esparto more or less accurately, while
the microscopical test is based upon the relative proportions as
represented by the volume of fibres of each class on the glass slip
placed under the microscope. Since the wood pulp consists of a number
of broad flat ribbon-like fibres, and the esparto of small cylindrical
fibres, considerable practice is necessary in making a proper analysis
of the two constituents in paper.

[Illustration: FIG. 25.--Esparto Pulp.]


STRAW.

The use of straw for the manufacture of paper was first brought
prominently into notice about the year 1800 by Matthias Koops, who
published a book printed on paper made from straw, but it was not until
1860 that this material was used in any large quantity.

[Illustration: FIG. 26.--A Cylindrical Digester for Boiling Fibre.]

Straw is now converted into a bleached paper pulp for news and
printings, and is also utilised for the manufacture of straw boards.

The production of a white paper pulp from straw is carried out in a
manner similar to that used in the case of esparto fibre, viz., by
digestion with caustic soda under pressure and subsequent bleaching.
As the straw contains considerable quantities of siliceous matter, the
chemical treatment necessary to reduce the material to paper pulp is
more severe, a stronger solution of caustic soda being used, and the
process of digestion being carried out at a higher temperature.

For the best quality of straw cellulose, the material is cut up into
small pieces by machines which resemble an ordinary chaff-cutter, and
the knots taken out by a separating machine. In most cases, however,
the whole straw is simply cut up into small lengths of about one to
two inches long, and placed at once in the digester. When the straw is
contaminated with foreign weeds, sand, husks, and similar substances,
as is usually the case, it is carefully hand-picked by girls, who
remove these impurities, which tend to produce particles of unbleached
matter in the finished pulp. The expense of this preliminary cleaning
process is more than compensated for by the enhanced value of the
bleached straw pulp.

_Digesting._--The cut straw is boiled in rotary cylindrical or
spherical vessels, stationary upright boilers of the vomiting type
being seldom employed because the circulation of the caustic soda
liquor does not take place freely with straw packed in the latter.

As the material is very bulky, some of the liquor is first put into the
boiler and the steam admitted while the straw is being thrown in. By
this means the straw is softened and reduced in bulk, so that a larger
quantity can be added before the digester is quite full. The full
amount of caustic soda is then made up by further additions of liquor,
and the contents of the digester heated by high-pressure steam for four
to six hours.

The conditions of treatment are shown by the following trial:--

      Amount of straw                   5,600 lbs.
      Caustic soda, 20 per cent.        1,120 lbs.

The caustic soda was added in the form of a liquor, having a volume of
2,012 gallons and a specific gravity of 1·055.

      Time of boiling                 5 hours.
      Pressure                        60 lbs.

_Washing._--The boiled straw is discharged into large tanks placed
below the digester and washed with hot water, the smallest possible
quantity being used consistent with complete washing in order to
prevent the accumulation of large volumes of weak lye. The spent liquor
and washing waters are drained off into store tanks and evaporated in a
multiple effect apparatus by the same process as that used for esparto
pulp. The last washings are usually run away because the percentage of
soda in them is too small to pay for the cost of recovery.

The final washing of the straw pulp is completed by the use of a
breaking engine or potcher. As straw pulp contains a large proportion
of cellular matter which cannot be regarded as true fibres, there
is always a danger of considerable loss in yield if the use of the
breaking engine is extensively adopted, because the short cells escape
through the meshes of the drum-washer. The washing is most economically
effected in the tanks if a good yield of pulp is required.

_Separating out Knots._--The broken pulp from the breaking engines is
diluted with large quantities of water and pumped over sand traps in
order to remove knots and weeds which have resisted the action of the
caustic soda. These traps consist of long shallow trays, perhaps sixty
to eighty yards long, one yard wide, and nine inches deep, containing
boards which stretch from side to side, sloping at an angle, and nailed
to the bottom of the trays. The dilute pulp flows through the trays,
leaving the heavy particles, knots, and foreign matter behind the
sloping boards, and finally passes over the strainers, which retain
any large coarse pieces still remaining.

_Making Sheets of Pulp._--The mixture from the strainers contains a
large excess of water which has to be removed before the pulp can be
bleached. For this purpose a wet press machine (see page 103) or a
presse-pâte (see page 85) is employed, and the wet sheets of pulp are
then ready for bleaching.

_Bleaching._--The process by which the pulp is bleached is exactly
similar to that used for treating esparto.

From 1870 to 1890 large quantities of straw were used for the
manufacture of newspaper in conjunction with esparto and wood pulp, but
the price of the material was gradually advanced so that it could not
be used with advantage, especially as the production of wood pulp gave
a material which was much cheaper, and which could be utilised at once
without chemical treatment.

In the manufacture of newspaper the tendency during recent years has
been to make the paper mill operations as mechanical as possible and to
dispense with the preliminary operations which are essential for the
manufacture of half-stuff, the chemical processes being left in the
hands of the pulp manufacturers.

The manufacture of straw cellulose is now practically confined to
Germany, but small quantities of the bleached straw cellulose are
imported because the pulp imparts certain qualities to paper which
improve it, notably in making cheap printing papers harder and more
opaque.


MICROSCOPICAL FEATURES OF STRAW.

The paper pulp obtained from straw consists of a mixture of short
fibres together with a large proportion of oval-shaped cells. The
fibres are short and somewhat resemble esparto, but the presence of
the smaller cells is a sure indication of the straw pulp. The fibres
themselves closely resemble the fibres of esparto, but as a rule the
latter are long slender fibres, while the straw fibre is very often
bent and twisted or slightly kinked.

[Illustration: FIG. 27.--Straw.]

The only method of distinguishing between straw and esparto is by
examination with the microscope. There is no chemical reagent known
which will produce a colour reaction on a paper containing straw that
will serve to distinguish it from a paper containing esparto. If such
papers are gently heated in a weak solution of aniline sulphate a pink
colour is slowly developed, the intensity of which is to some extent a
measure of the amount of straw or esparto present.

Straw and esparto are usually described in text-books under one
heading, partly because the fibres possess strong resemblances in
physical and chemical constitution, and partly because the methods of
manufacture are identical. At the same time the qualities of the two
pulps are so different that they cannot be used indiscriminately, the
one for the other. Straw cellulose cannot be utilised in the place
of esparto, particularly for light bulky papers. Hence in magazine
and book papers containing a fibre which gives a pink coloration with
aniline sulphate it is fairly safe to assume that esparto pulp is
present.




CHAPTER V

WOOD PULP AND WOOD PULP PAPERS


THE MANUFACTURE OF MECHANICAL WOOD PULP.

Wood is converted into pulp suitable for the manufacture of paper by
methods which produce two distinct varieties. The first is _mechanical
wood pulp_, so called because it is made by a purely mechanical
process. The second is termed _chemical wood pulp_ from the fact that
the material is submitted to chemical treatment.

_Ground Wood and Cellulose._--The two varieties of pulp are sometimes
distinguished by the use of the terms ground wood and cellulose. In
the former case the description implies a product consisting of pulp
obtained by grinding wood into a fibrous condition, while in the second
the word suggests a purified chemical product freed from the resinous
and non-fibrous constituents found in wood. This is, in fact, the
essential difference, for mechanical wood pulp consists of fibres which
have been torn away from wood by means of a grindstone; it differs
but slightly in chemical composition from the original raw material
and contains most of the complex substances natural to wood. Chemical
wood pulp, on the other hand, consists of fibre isolated from wood in
such a manner that the complex non-fibrous substances are more or less
entirely removed. The difference between these two pulps is shown in
the following approximate analysis of spruce wood, and of the pulp
derived from it. The composition of the mechanical pulp is practically
identical with that of the wood itself.

COMPOSITION OF SPRUCE WOOD, AND OF CHEMICAL WOOD PULP (SPRUCE).

      ----------------+---------+----------
             --       |  Wood   | Chemical
                      |(Spruce).|Wood Pulp.
      ----------------+---------+----------
      Cellulose       |  53·0   |  88·0
      Resin           |   1·5   |   0·5
      Aqueous Extract |   2·5   |   0·5
      Water           |  12·0   |   8·0
      Lignin          |  30·5   |   2·5
      Ash             |   0·5   |   0·5
                      +---------+----------
                      | 100·0   | 100·0
      ----------------+---------+----------

The use of mechanical wood pulp is generally confined to the
manufacture of news, common printings and packing papers, cardboards,
and boxboards. It possesses very little strength, quickly discolours
when exposed to light and air, and gradually loses its fibrous
character. The chemical wood pulp is a strong fibre, from which
high-class papers can be manufactured, the colour and strength of which
leave little to be desired.

_Species of Wood._--The woods most commonly used for the manufacture
of wood pulp belong to the order Coniferæ, or cone-bearing trees.
In Europe the spruce and silver fir are the chief species, while in
America spruce, balsam, pine, and fir are employed. The harder woods,
such as hemlock, beech, larch and others, are not converted into pulp
by the mechanical process.

_Timber Operations._--The trees are cut down in the early part of
winter by gangs of men specially trained to the work. The organisation
of a lumber camp when the operations are of an extensive character is
very complete and carefully arranged, every detail being attended to
in order to get out the wood as cheaply and expeditiously as possible.
The branches and small tops are removed from the trees when they are
fallen, and the trunks cut into logs of 12, 14, or 16 feet in length,
and afterwards piled up on the banks of the nearest river, or on the
ice, ready for the breaking up of the winter.

As soon as the ice breaks up and the rivers become navigable the logs
are floated down to their destination, in some cases hundreds of miles
from the scene of operations. Where rivers are not available the timber
is brought out by horses or bullocks, or by means of a light railway.

_Log Cutting._--As the timber arrives at the mill it is carefully
measured, both as to its diameter and length, in order that a record
may be kept of the quantity used. Some of the logs are piled up in
the storeyard for use in the winter, and the remainder converted into
pulp day by day. The logs are first cut into short pieces about 2 feet
long by means of a powerful circular saw, the arrangements for this
work being devised so as to keep down the cost of labour as much as
possible. All waste pieces are thrown aside to be utilised as fuel.

_Barking._--The bark on the logs is removed in one or two ways. Much
of it is knocked off during the transfer from the forest to the mill,
but even then the wood requires to be cleaned. In Norway and Sweden
the wood is treated in a _tumbler_ or a _barker_, while in America and
Canada the use of the tumbler is practically unknown.

The barker consists of a heavy iron disc fitted with knives, usually
three in number, which project from the surface of the disc about
half or three-quarters of an inch. The barker rotates in a vertical
position, and the short pieces of wood are brought one by one into
contact with the disc in such a manner that the bark is shaved off by
the knives. The machine is provided with conveniences for pressing the
wood against the disc and for turning the logs as they are barked.

[Illustration: FIG. 28.--A Pair of Barkers for removing Bark from Logs
of Wood.]

The machine is encased in a strong cast-iron cover, and all the bark
shaved off is carried away by the strong current of air set up by the
rapid motion of the disc, and subsequently burnt.

The tumbler system is quite different. In this case the short pieces
are thrown into a large circular drum with hot water, and the bark
taken off by the friction of the pieces as the drum rotates. The loss
of material is of course less in this process, but the wood is not
cleaned quite so effectively.

[Illustration: FIG. 29.--View of Horizontal Grinder (A), with Section
(B).]

The wood at this stage can be used either for the manufacture of
mechanical or chemical pulp. As a general rule the pieces are taken
indiscriminately for either process, but sometimes the wood is sorted
out, the clean stuff free from knots and blemishes being reserved for
high quality chemical pulp.

_Grinding._--The main feature of the grinding process is the attrition
of the wood when held against the surface of a rapidly revolving
grindstone, the fibres as they are rubbed off being instantly carried
away from the stone by a current of water. A complete description of
the machines used and the modifications of the process practised by
manufacturers is impossible in this book, but the following points will
be sufficient.

The machine consists of a large grindstone about 54 inches in diameter,
and 27 inches thick. It rotates in a vertical or in a horizontal
position at a high speed. The stone revolves inside a casing which is
provided with a number of _pockets_, so called, into which the pieces
of wood are thrown at regular intervals, as fast as the wood is ground
by the friction of the stone.

A continual stream of water playing upon the surface of the stone
washes away the pulp into a tank or pit below the machine.

The quality of the pulp may be varied by the conditions under which it
is made. By limiting the proportion of water so that the wood remains
in contact with the stone for a longer time the temperature of the mass
in the pockets rises. Such _hot ground pulp_, as it is termed, is tough
and strong.

When the fibres are washed away from the stone as fast as they are
produced the temperature does not rise, and _cold ground_ pulp is made,
which is not characterised by the somewhat leathery feel of the pulp
made at the higher temperature.

The surface of the stone plays an important part also. If the stone
is smooth the wood is rubbed away slowly, but if the surface has been
roughened and grooved by means of a special tool the fibres are torn
away quickly. In the first case the pulp comes from the stone in a
finely-ground state and in a uniform condition, while in the second
the pulp is coarse and chippy.

The output of the machine is, however, much increased by the use of
sharp stones and by the application of considerable pressure to the
blocks of wood.

[Illustration: FIG. 30.--A Vertical Grinder for making Hot Ground
Mechanical Wood Pulp.]

_Screening._--The mixture of water and pulp leaving the grinder falls
into a tank below the stone, all large chips being retained by means
of a perforated plate. The finer pulp, still too coarse for use, is
then pumped to the screens, which serve to remove all chippy and coarse
fibres and produce a uniform material. The _shaking sieve_ consists
of a shallow tray, the bottom of which is a brass plate or series of
plates perforated with small holes or slits. The pulp flows on to the
tray, which is kept in a state of violent agitation, the fine pulp
passing through the holes and the coarser pieces working down to the
lower edge of the tray into a trough which carries them away. The _flat
screen_ is somewhat different in construction, but the principle of
separation is the same. It consists of brass perforated plates forming
the bottom of a shallow cast-iron tray, continually agitated by means
of cams fixed to the under surface of the trays.

[Illustration: FIG. 31.--Centrifugal Screen for Wood Pulp.]

The _centrifugal screen_ is a cage made of finely perforated brass
sheeting which revolves at a very high rate of speed inside a circular
cast-iron vessel. The pulp flows into the interior of the cage, the
fine fibres being forced through the screen by the centrifugal action
of the machine, and the coarse material is retained.

[Illustration: FIG. 32.--Section of Centrifugal Screen for Wood Pulp.]

_Wet Pressing._--The pulp leaving the screens is mixed with such a
large quantity of water that it is necessary to concentrate it. This
is effected by means of the wet press machine (Fig. 41). The pulp and
water are pumped into a wooden box in which revolves a large hollow
drum, the surface of this drum consisting of a fine wire cloth of about
60 or 70 mesh. The drum is not entirely immersed in the mixture, so
that as it rotates the pulp forms a skin or thin sheet on the surface,
and the water passes away through the wire into the interior of the
hollow drum. The drum carries the thin sheet out of the box and above
the level of the mixture until it comes into contact with an endless
blanket or felt, which is pressed against that part of the drum not
immersed in the liquid.

By this means the thin sheet is transferred to the felt and carried
between squeezing rolls to the finishing rolls. The felt, carrying on
its upper surface the thin sheet of pulp, passes between two rolls,
usually 16 to 20 inches in diameter, the upper being made of wood and
the lower one of cast iron. The pulp adheres to the upper drum and the
felt passes round the lower drum back to the box containing the mixture
of pulp and water; the thin sheet is continuously wound on the upper
roll until a certain thickness is reached.

When this occurs the attendant removes the thick sheet by a dexterous
movement of a sharp stick across the face of the roll. The wet pulp at
this stage consists of 30 per cent. air-dry pulp and 70 per cent. of
water.

_Hydraulic Pressing._--The sheets taken from the wet press machine are
folded into a convenient shape and piled up, coarse pieces of sacking
being placed between the sheets. At stated intervals the piles are
submitted to pressure in hydraulic presses in order to remove further
quantities of water, which slowly drains away through the sacking. In
this way a mass of pulp in the form of thick folded sheets containing
50 per cent. of dry wood pulp is produced.

The pieces of sacking are taken out and the sheets put up in bales of
any required weight, usually 2 cwt. or 4 cwt.


THE MANUFACTURE OF CHEMICAL WOOD PULP.

Most vegetable fibres are converted into pulp by alkaline processes,
that is by digesting the raw material with caustic soda and similar
alkaline substances. Wood may be treated in two ways, one of which is
the ordinary soda process, and the other an acid treatment requiring
the use of sulphurous acid.

_Preparation of the Wood._--The logs of wood are cut up and barked
exactly as in the case of mechanical pulp. The short two-foot pieces
are then cut up into small flakes about one inch square and half an
inch thick by means of a machine known as a _chipper_. This is similar
in construction to a barker, consisting of a heavy iron disc rotating
at a high speed inside a stout cover. The disc revolves in a vertical
position, and three projecting knives slice up the logs into flakes.
For this purpose the disc is provided with three slots which radiate
from the centre towards the circumference for about 12 inches. The
knives can be adjusted so that they stand up through the slots and
above the surface of the disc to any required distance.

In order to ensure uniformity in the size of the chips, the practice
is frequently adopted of sifting the wood leaving the chipper. The
sieve is a large skeleton drum, the outer surface of which is made of a
coarse wire cloth capable of passing all pieces of the size mentioned.
Larger chips and pieces are retained in the drum as it revolves in a
horizontal position and only fall out on reaching the extreme end of
the machine.

_The Digesters._--The object of boiling the wood under pressure with
chemicals is to dissociate the valuable fibrous portion of the plant
from the resinous and non-fibrous portion. In this process the wood
loses half its weight, the yield of pulp being about 50 per cent., and
the remainder is dissolved out by the chemical solution. The conditions
of treatment are extremely varied in character, the quality of the pulp
produced varying in proportion.

The digesters are either spherical, cylindrical, or egg-shaped, being
constructed to revolve at a slow rate of speed, or fixed permanently
in an upright position. Spherical boilers are usually 9 or 10 feet in
diameter, the cylindrical digesters being 40 or 50 feet high and 12 or
15 feet diameter, the larger ones being capable of taking 20 tons of
wood for each operation.

[Illustration: FIG. 33.--Wood Pulp Digester, partly in elevation,
partly in section.]

For the alkaline process the interior of the digester does not require
any special treatment, but with the acid process the internal portion
of the boiler is carefully lined with a thick layer of acid-resisting
brick and cement.

The contents of the digester are heated by means of high-pressure
steam, which is blown direct into the mass or passed through a coil
lying at the bottom of the vessel. In the former case the steam is
condensed by the liquor, the volume of which is consequently increased,
while in the latter case the condensed steam is drawn off continuously
from the pipes. Each system has its own particular advantages.

_Different Kinds of Chemical Wood Pulp._--According to the method of
treatment so the quality of the pulp varies. The chemicals used, the
system of boiling, the temperature of digestion, the strength of the
solutions, the duration of the cooking period, and, last but not least,
the species of wood, are all determining factors in the value of the
ultimate product.

_Soda Pulp._--This is prepared by digesting wood with caustic soda in
revolving boilers for eight or ten hours at a pressure of 60 to 80 lbs.

_Sulphate Pulp._--Prepared by digesting the wood with a mixture of
caustic soda, sulphide of soda, and sulphate of soda.

_Sulphite Pulp._--The process most generally adopted for the
manufacture of wood pulp is the treatment of the material in
brick-lined digesters with bisulphite of lime for eight to nine hours
at a pressure of 80 lbs.

_Mitscherlich Pulp._--This is sulphite pulp prepared by digesting the
wood at a much lower temperature and for a longer period than the
ordinary sulphite. The steam is not blown direct into the mass of wood,
and the pressure seldom exceeds 45 or 50 lbs., the time of boiling
occupying 45 to 50 hours. So called from the name of the inventor.

_Sulphite Wood Pulp._--This name is given to pulp prepared by digesting
wood with solutions containing sulphurous acid, or salts of sulphurous
acid. The acid is produced by burning sulphur or certain ores
containing sulphur, such as copper or iron pyrites, in special ovens.
The most modern form of oven consists of a cylindrical cast-iron drum
revolving slowly in a horizontal position on suitable bearings. The
sulphur is thrown at intervals, or fed automatically, into the oven,
the amount of air being carefully regulated to avoid the formation of
sulphuric acid in the later stages of preparation. The sulphur is also
burnt in stationary ovens which consist of flat shallow closed trays.

[Illustration: FIG. 34.--View of ordinary Sulphur-burning Ovens.]

The hot sulphurous acid gas passes through pipes and is cooled, after
which it is brought into contact with water and lime for the production
of the bisulphite of lime. This is accomplished by one of two methods
as follows.

_Tower System._--The cool gas is drawn into high towers usually
built of wood, 7 or 8 feet diameter, which are filled with masses of
limestone. From tanks at the top of each tower a carefully regulated
quantity of water flows down upon the limestone and absorbs the
ascending column of gas, this being drawn into the tower from the
bottom. The limestone is simultaneously dissolved, and the liquid
which flows out from the pipes at the bottom of the tower consists of
lime dissolved in sulphurous acid, together with a certain proportion
of free sulphurous acid. This is generally known as a solution of
bisulphite of lime.

_Tank System._--The somewhat costly tower system has in many cases been
superseded by the use of a number of huge wooden vats, 10 to 12 feet
diameter and 8 to 10 feet high. These tanks are filled with water and
a known quantity of slaked lime. The gas is forced into the tanks by
pressure or drawn through by suction, and the conversion of the milk of
lime into bisulphite of lime proceeds automatically. In order to ensure
complete absorption the gas passes through the tanks in series, so that
the spent gases leaving the vats do not contain any appreciable amount
of sulphurous acid.

In order to obtain pulp of uniform quality it is necessary that the
liquor should be of constant composition. The formula differs in the
various mills according to the conditions which are found most suitable.

_Sulphite Digesters._--The almost universal form of boiler employed in
cooking wood by the sulphite process is a tall cylindrical vessel of
about 50 feet in height, and 14 to 15 feet internal diameter, lined
with acid-resisting brick.

This form of digester is capable of holding 20 tons of wood at one
charge, yielding 10 tons of finished pulp.

The chipped wood is discharged into the digesters from huge bins
erected just above the openings to the digesters, so that the latter
can be filled without any delay and the requisite quantity of sulphite
liquor added.

The manhole or cover is at once put on, securely fastened, and steam
turned on gradually until the pressure reaches 70 or 80 lbs., at which
pressure the cooking is steadily maintained. The progress of the
operation is watched and samples of the liquor drawn from the boiler
at intervals to be tested, so that the boiling may be stopped when the
results of the testing show the wood is sufficiently cooked.

There is no special difficulty in this operation, provided the
necessary conditions are observed. It is important that the wood should
be dry, and that the proportion of sulphite liquor per ton of dry wood
should be constant. If the wood happens to be wet, due allowance must
be made for the excess water and a somewhat stronger liquor used in
order to compensate for this. Other precautions of a similar character
are observed in order to minimise the danger of an insufficiently
cooked pulp.

_Washing._--When the pulp has been boiled, a process which generally
occupies seven or eight hours, the steam is shut off and the contents
of the boiler blown out into large vats known as blow-out tanks, the
pressure of steam remaining in the digester being sufficient to empty
the softened pulp in a few minutes. Much of the spent sulphite liquor,
now containing the dissolved resinous and non-fibrous portions of the
original wood, drains away from the mass in the tank, and then copious
supplies of clean water are added in order to wash out the residual
liquors which it is essential to remove.

Numerous other devices are employed to ensure the complete washing of
the boiled pulp.

_Screening._--The production of a high-class pulp necessitates proper
screening to eliminate coarse pieces of unboiled wood and the knots,
the latter not being softened completely. The methods adopted vary
according to requirements.

For uniform clean pulp that can be bleached easily the material from
the blow-out tanks is, after washing, mixed with large quantities of
water and run through sand traps, which consist of long shallow wide
boxes provided with slanting baffle-boards to retain knots and large
pieces of unsoftened wood, the pulp thus partially screened being
subsequently treated in the proper screening apparatus.

Sometimes the washed pulp is sent direct to the screens and the
well-boiled fibres sorted out by a system of graded screens, which
separate the completely isolated fibres from the bulk and retain the
larger pieces, these being broken down in a suitable engine and put
back on the screens.

The machinery employed for screening chemical pulp is identical with
that used for the treatment of mechanical wood pulp.

_Finishing._--The ordinary sulphite pulp is worked up into the form
of dry sheets for the market and not sent out in a wet state as the
mechanical wood. There are several practical disadvantages in preparing
the latter in a dry condition which do not, however, occur with
chemical pulp.

Hence the pulp after being screened is not pressed but submitted to a
different process. From the screens the mixture of pulp and water, the
latter being present in large quantity, is pumped into a concentrator,
or slusher, as it is termed, by means of which some of the water is
taken out.

The slusher consists of a wooden box divided into two compartments by
a vertical partition. In the larger compartment a hollow drum covered
with a fine wire cloth revolves, the construction and purpose of which
are precisely the same as that of the wet press machine used for
mechanical pulp.

As the drum revolves the pulp adheres to the outer surface, while
the water passes through the wire cloth. The drum is not completely
immersed in the mixture, so that the skin of pulp is brought out of the
water by the rotation of the drum. When this takes place the contact of
a wooden or felt covered roll which revolves on the top of the drum
causes the pulp to be transferred from the drum to the roll. The wet
pulp is continuously scraped off by an iron bar or _doctor_, as it is
called, resting on the surface of the roll, and it finally drops into
the second compartment of the slusher in a more concentrated form ready
for the drying machine.

_Drying._--The mass of wet pulp from the slusher is conveyed into a
circular reservoir or _stuff chest_, which serves to supply the machine
used for converting the pulp into dry sheets.

The machine is to all intents and purposes a Fourdrinier paper machine,
and the process is similar to that used for the manufacture of paper.
The pulp flows in a continuous stream on to a horizontal endless wire,
which carries it forward as a thin layer; the water drains through
the meshes of the wire, further quantities being removed by _suction
boxes_, which draw away the water by virtue of the vacuum produced by
special pumps. The wet sheet then passes between the _couch rolls_
which compress the pulp, squeezing out more water, and then through
_press rolls_, which finally give a firm adherent sheet of pulp
containing 70 per cent. of water. The sheet is dried by passing over
a number of steam heated cylinders, which cause all the moisture to
evaporate from the pulp. At the end of the machine the dry pulp is cut
up into sheets of any convenient size, and packed up in bales of two or
four cwts.

_Mitscherlich Sulphite Pulp._--This term is applied to sulphite wood
prepared by submitting the chipped wood to a comparatively low pressure
for a long period. The wood is placed in the stationary upright form of
digester with the requisite amount of liquor, and the heating produced
by the passage of steam through a leaden coil lying at the bottom of
the digester, so that the steam does not condense in the liquor but
in the coil, from which it is drawn off. The pressure seldom exceeds
45 lbs. but the duration of the cooking is thirty-six to forty-eight
hours. The boiler is not emptied under pressure, but the pulp is
discharged from the digester after the pressure has been lowered, and
the manhole taken off. The contents are usually shovelled out by the
workmen.

The pulp is carefully washed, screened and made up into wet sheets
on the ordinary wet press machine. This pulp is never dried on the
Fourdrinier like the common sulphite, as its special qualities can only
be preserved by the treatment described. This pulp is particularly
suitable for parchment papers, grease proofs and transparent papers.

_Soda Wood Pulp._--The chipped wood is boiled in stationary or
revolving digesters for eight or nine hours at a pressure of 70 or 80
lbs. A solution of caustic soda is employed, about 16 to 20 per cent.
of the weight of the wood being added to the contents of the digester.
Live steam is blown direct into the mass, and after the operation the
spent liquor is carefully kept for subsequent treatment. The pulp is
washed in such a manner that the amount of water actually used is kept
down to the smallest possible volume consistent with a complete removal
of soluble matters. This is done in order that the spent liquors may be
treated for the recovery of the soda.

_Recovery of Spent Liquors._--When wood is cooked by the soda and
sulphate processes the solutions containing the dissolved organic
matter from the wood can be evaporated, and the original chemical
recovered. In the case of soda pulp the method of treatment is as
follows: the spent liquors and the washings are evaporated by means of
a multiple effect vacuum apparatus to a thick syrup. The concentrated
liquor produced is then burnt in special furnaces, all the organic
matter being consumed, leaving a black mass which consists mainly
of carbonate of soda. The mass is washed with water to remove the
carbonate which is afterwards converted into caustic soda by being
boiled with lime.

[Illustration: FIG. 35.--Spruce Wood Pulp.]

The spent liquors from the sulphite process have no value, for they
cannot be recovered by this method. At present the whole of the sulphur
used and the organic matter dissolved from the wood is lost. This means
the loss of about 250 to 350 lbs. of sulphur and nearly 50 per cent. of
the weight of wood for every ton of pulp produced.


WOOD PULP; MICROSCOPIC FEATURES.

[Illustration: FIG. 36.--Mechanical Wood Pulp.]

Mechanical and chemical pulps are readily distinguished under the
microscope. The former consists of fibres of irregular shape and size,
mixed with a large proportion of structureless particles, all bearing
evidence of having been torn apart and separated by mechanical methods.
The chemical pulp, on the other hand, consists of fibres isolated by a
process which preserves them in perfect condition and form. The pulp
from the various woods can be differentiated by minute details in fibre
structure, some of the woods being determined from the presence of
characteristic cells.

The use of aniline sulphate can also be resorted to, and for
microscopic work the most useful reagent is a mixture of zinc chloride
and iodine. This produces an intense yellow colour with mechanical pulp
and a bluish colour with sulphite and other chemical wood pulps.


THE DAILY NEWSPAPER.

The newspapers of the present day are made almost exclusively of wood
pulp. The use of the latter material for paper-making has steadily
increased from the date of its introduction about A.D. 1870, when wood
pulp was imported into England in considerable quantities.

News and cheap printings consist of mechanical and chemical wood pulps
mixed in varying proportions determined chiefly by the price paid
for the finished paper. In some cases the proportion of mechanical
wood pulp is as much as 85 per cent., though the average composition
of a cheap wood paper is represented by the following proportions:
Mechanical pulp, 70 per cent.; sulphite pulp, 20 per cent.; loading, 10
per cent.

Some idea of the enormous quantity of material used for the daily
press may be judged from one or two examples. A certain popular weekly
newspaper having a circulation of one and a quarter million copies per
week requires every week 137 tons of paper produced from 170 tons of
wood. A popular halfpenny newspaper boasting a circulation of about
one-half million copies per day consumes 185 tons of paper manufactured
from 230 tons of wood, every week.

It is easy also from these facts to estimate the amount of timber
which must be cut down to supply the demand for newspapers and cheap
printings.

The manufacture of news calls for considerable skill and able
management, owing to the keen competition amongst the paper mills
devoted to this class of paper. The process as carried on in England is
as follows:--

The mechanical pulp, reaching the mill in the form of thick sheets
suitably packed up into bales, is first broken up again into moist
pulp. Various machines are used for this, such as Wurster's kneading
engine, Cornett's breaker, or some similar contrivance. An old potcher,
such as is used for the breaking and washing of rags, makes a good pulp
disintegrator. The broken pulp is discharged into beating engines in
any suitable or convenient manner and the right proportion of chemical
wood pulp added in the form of dry sheets. The beating process only
occupies thirty to forty minutes in the case of the common news, a
marked contrast to the eight or nine hours required by rags. China clay
is added to the contents of the beater, ten to twelve per cent. being
the general practice. This is followed by a measured quantity of rosin
size, and after thorough incorporation the size is precipitated upon
the fibres by means of alum.

In the commoner qualities of these papers the materials are added in
the dry state, but for finer grades of newspaper the china clay is
mixed with water, and carefully drained through a fine sieve before
use. The alum cake is also dissolved and treated in a similar manner in
order to keep out dirt and coarse particles likely to produce holes in
the paper.

The paper machine used for the manufacture of cheap printings is
constructed to produce as much as 100 to 180 tons of finished paper per
week, every detail being arranged for a large output at a very high
speed. In the modern machine it is possible to produce paper at the
rate of 450 to 550 feet per minute, the width of the sheet being from
120 to 160 inches.

Careful attention is paid to economy of every kind with regard to the
power required for driving the machine, the amount of steam consumed
in drying the paper, recovery of excess of fibre and china clay which
escapes from the machine wire, and similar details of a mechanical
order.

[Illustration: FIG. 37.--The Screens for removing Coarse Fibres from
Beaten Pulp.]

The beaten pulp, after being sized and coloured, is discharged into
huge circular brick tanks, or stuff chests, two of which are found
with each paper machine. The supply of pulp and water for the machine
is taken from one stuff chest while the second is being filled up
from the beating engines, in order to secure a mixture of constant
composition.

[Illustration: FIG. 38.--The Paper Machine (wet end showing wire).]

The pulp is pumped from the stuff chest into a small regulating box
placed above the machine wire, and this box is kept full of beaten
pulp so that the supply of pulp and water to the machine is perfectly
constant. The pulp, diluted with the proper quantity of _back-water_,
is carefully strained through rotary screens and allowed to flow
through a distributing box on to the machine wire, where it rapidly
forms a sheet of paper.

The excess of water, together with a certain proportion of fine
fibre and china clay, falls through the wire, and is caught below
in a shallow box, called the save-all. This _back-water_, as it is
called, is used over again for diluting the beaten pulp to the right
consistency, as already described.

The whole of the water obtained in this way is not all utilised in the
regulating box, and any surplus is pumped up continually into large
store tanks and used in the beating engines for breaking down the dry
pulp.

In many cases, where a large quantity of water is used on the machine,
special methods have to be adopted for the recovery of all the fibre
and clay, which would otherwise be lost, and there are many ingenious
systems in use whereby this saving is effected.

The most usual practice is to allow the excess of water, which contains
from 8 to 15 lbs. of suspended matter per thousand gallons, to flow
through a series of brick tanks at a slow rate of speed. The clay and
fibre settle to the bottom of the tanks, and the water passes away from
the last tank almost clear and free from fibre and loading.

The drying of the moist paper leaving the press rolls of the machine is
effected in the usual manner by means of drying cylinders. On account
of the great increase of speed at which the paper is produced, the
number of drying cylinders has also been increased, and at the present
time a machine of this description is provided with 28 or 32 cylinders,
the object being to dry the paper economically.


MECHANICAL WOOD PULP IN PAPER.

The presence of mechanical wood pulp in paper is detected by means of
several reagents, which produce a definite colour when applied to a
sheet of paper containing mechanical wood. The depth of colour obtained
indicates approximately the percentage present, but considerable
practice and experience is necessary to interpret the colour exactly. A
more reliable method of estimating the percentage of mechanical wood in
a paper is by microscopic examination.

The reagents which can be used are--

(1) _Nitric Acid._--This produces a brown stain on the paper, but it is
not a desirable reagent for ordinary office purposes.

(2) _Aniline Sulphate._--A solution of this is prepared by dissolving 5
parts of aniline sulphate in 100 parts of distilled water. When applied
to the surface of news a yellow coloration is produced, more or less
intense according to the amount of mechanical wood present. It can only
be used with white papers, or papers very slightly toned.

(3) _Phloroglucine._--This sensitive reagent, which gives a rose-pink
colour when brushed on to the surface of the paper, is prepared by
dissolving 4 grammes of phloroglucine in 100 c.c. of rectified spirits,
and adding to the mixture 50 c.c. of pure concentrated hydrochloric
acid.

There are several other aniline compounds which give colour reactions
of a similar character, but they are not often used. The phloroglucine
reagent fails as a test for mechanical wood in papers which have
been dyed with certain aniline colours, for example, metanil yellow.
Paper which has been coloured with this dye will, when moistened with
the phloroglucine reagent, give an intense pink colour, even if no
mechanical wood is present. This is due to the fact that the dye itself
is acted upon by the hydrochloric acid in the test reagent. The same
colour is produced on the paper with hydrochloric acid _per se_.

There is little difficulty in distinguishing between the colour arising
from the presence of such a dye, because the effect is instantaneous,
whereas the coloration due to mechanical wood develops gradually.
Moreover, the reaction due to the presence of metanil yellow gives a
perfectly even coloured surface, whereas with mechanical wood pulp the
fibres appear to be more deeply stained than the body of the paper.

_Output of a Paper Machine._--The quantity of paper which can be
produced on the paper machine is readily calculated from the following
data:--

        Speed of machine in feet per minute   _F_
        Nett deckle width in inches           _D_
        Width of sheet of paper in inches     _W_
        Length of sheet of paper in inches    _L_
        Number of sheets in ream              _S_
        Weight of paper per ream              _R_

The general formula for the output of paper per hour is

                                720 × _F_ × _D_ × _R_
      Output in lbs. per hour = -----------------------.
                                   _S_ × _L_ × _W_

When the number of sheets in the ream is 480, this formula simplifies to

                                1½ × _R_ × _F_ × _D_
      Output in lbs. per hour = --------------------.
                                     _L_ × _W_

The term "nett deckle width" applies to the width of the trimmed
finished paper at the end of the machine. The formula takes no account
of the allowance required for trimming edges. In most cases the deckle
width of the machine is arranged so that the paper is cut into strips
of equal width when leaving the calenders, _e.g._, a deckle of 80
inches will give 4 sheets, each 20 inches wide.

[Illustration: FIG. 39.--Paper Machine showing Wire, Press Rolls, and
Drying Cylinders.]

The method by which the general formula is obtained may be explained by
an example.

What is the output of a machine having a speed of 100 feet per minute,
with an 80-inch deckle, producing a sheet of paper 20 inches by 30
inches, weighing 30 lbs. per ream of 480 sheets?

The machine produces every minute a sheet of paper 100 feet long and 80
inches wide.

Hence output per minute in square inches

              = 12 × 100 × 80.
        Output per hour in square inches
              = 60 × 12 × 100 × 80.

Now each (20 × 30 × 480) square inches is area of one ream.

Output of paper per hour in reams

                60 × 12 × 100 × 80
              = ------------------.
                   480 × 30 × 20

Output of paper per hour in lbs.

                720 × 100 × 80 × 30
              = -------------------
                   480 × 30 × 20

              = 600 lbs.

The general formula may be applied for the purpose of calculating the
speed at which the machine must be driven.

_Example._--A machine with 75-inch deckle is required to produce
6 cwts. per hour of a paper 25 inches by 18 inches (500 sheets),
weighing 19 lbs. to the ream. At what speed is the machine to be driven?

Output in lbs. per hour

                720 × _F_ × _D_ × _R_
              = ---------------------
                   _S_ × _L_ × _W_

                720 × F × 75 × 19
          672 = -----------------
                  500 × 18 × 25

          _F_ = 148 feet per minute.




CHAPTER VI

BROWN PAPERS AND BOARDS


_Common Browns._--The raw material used in the manufacture of common
brown papers is chiefly jute and waste fibres of every description,
such as waste cuttings from boxboard factories, old papers, wood pulp
refuse, and other substances of a like nature. The jute, in the form
of sacking or old gunny bags, and the hemp refuse, in the shape of old
rope and string, are subjected to a slight chemical treatment just
sufficient to isolate the fibres to a condition in which it is possible
to work them up into paper. The bagging and string are cut up in a rag
chopper and boiled in revolving boilers with lime or caustic soda for
several hours at a pressure of 20-30 lbs., the lime being used when it
is desired to manufacture a harsh paper, and the caustic soda being
employed for the production of paper having a softer feel. The pulp is
not always washed very completely after the process of digestion, as is
the case with white papers, and it is often possible to extract from
brown papers of this class a considerable proportion of the alkaline
matter which has not been thoroughly removed from the boiled pulp.
The presence of this alkaline residue does not affect the quality of
ordinary brown paper, but is frequently a serious defect in the case
of middles or straw boards, which are afterwards utilised for boxes
and covered with coloured papers. The colour of the paper pasted on to
such incompletely washed boards is frequently spoilt by the action of
the alkali when moistened with the paste used, many aniline dyes being
susceptible to the small proportion of alkali present.

The stronger materials, such as jute or old rope and string, are either
used by themselves or blended with inferior raw material according
to the quality of the paper being made. The jute and hemp fibres are
generally beaten by themselves in the engine before the other materials
are added. The pulp is mixed with the required amount of loading, while
the sizing and colouring operations are carried out in the usual way.

The common brown papers are known by a variety of trade names which
at one time indicated the nature of the fibrous constituent, but at
the present day the name is no guide or indication of the material
used for the manufacture of the paper. The common heavy brown used for
wrapping sugar and sundry groceries made in heavy grey and blue shades
is a coarse paper made from cheap materials and containing a large
proportion of mineral matter. It is usually supplied under the trade
name of _royal_.

A somewhat lighter and stronger wrapping paper of a white or buff
colour, used for wrapping groceries, tea, and cotton goods, is that
known as _casings_, a name probably derived from the application of
this paper originally to the lining of cases.

_Manila papers_ so called were originally made from rope, but the term
is now applied to papers which may be made entirely of wood pulp.

_Rope browns_ are common papers made of fairly strong material of a
miscellaneous character, this name having been derived from the fact
that rope and similar fibre were at one time used exclusively.

_Wood Pulp Wrappers._--Most of the papers of the present day are made
from wood pulp, this material giving a thin, light, tough paper, which
is pleasant to handle and forms a great contrast to the dense, opaque,
heavily loaded, and inartistic specimens produced some years ago. Paper
of this kind, though apparently more expensive than common browns, is
really more economical in use. The paper is not only stronger, but it
is possible to obtain a larger number of sheets for a given weight.
The great advantage in the improvement of brown papers dates from
the introduction of the now well-known kraft papers, which are of
comparatively recent origin.

_Kraft Paper._--The term Kraft, meaning "strength," is applied to
a remarkably strong cellulose paper prepared from spruce and other
coniferous woods by the soda treatment, the special feature of the
process being an incomplete digestion of the wood.

The wood previously chipped into pieces 1 inch to 1½ inches in length,
is boiled with caustic soda, the digestion being stopped before the
wood pulp has been quite softened, and while the pulp is still too
hard to be broken up into isolated fibres by simple agitation in
water. The pulp after thorough washing is disintegrated by means of
an edge-runner, or some form of breaking engine, the first mentioned
probably giving the most satisfactory results, and converted into paper
by the usual methods.

The wood can also be reduced by the sulphate process, in which case the
chipped wood is boiled in a liquor to which about 25 per cent. of spent
lye from a previous cooking is added.

The best results are obtained by attention to the cooking process to
ensure an under-cooked pulp, by careful isolation of the fibres in a
kollergang, or edge-runner, which machine is capable of separating the
fibres without shortening them, and by proper manipulation on the paper
machine.

The paper produced under favourable conditions in this direction is
wonderfully tough and strong and may be quoted as the most recent
example of the fact that the latent possibilities of wood pulp have by
no means been exhausted or even thoroughly investigated.

_Imitation Kraft Paper._--If wood is boiled in water at high
temperatures the fibre is softened and much of the resinous matter is
removed. Such wood, if ground in the same way and by the same methods
as ordinary mechanical wood pulp, is readily disintegrated, and a
long-fibred pulp may be obtained. The process of boiling short 2 feet
logs of wood in a digester under a pressure of 20-50 lbs. has long
been known. The wood after boiling is partly washed and then worked
up into pulp by the usual mechanical process. The wood is easily
ground and yields pulp containing long fibres which in their physical
properties closely resemble those of pure wood cellulose, but the
original constituents of the wood are present almost unchanged, just
as in mechanical pulp. The product obtained by grinding is a very
tough flexible material of a brownish yellow colour, and the paper is
known as _Nature brown_. It is chiefly used for the preparation of
tough packing papers, for the covers of cheap pocket-books, and other
miscellaneous purposes. When this brown mechanical wood pulp paper is
glazed on both sides it is then known as _ochre glazed_, the word ochre
referring to the colour. When made up into light weight papers it is
sold as _imitation kraft paper_.

A great variety of wrapping papers are now made from wood pulp, such
as _sealings_, _sulphite browns_, _manilas_, _sulphite caps_, but the
distinctions between these papers relate chiefly to the amount of
finish, the colour and size of the sheet. The methods of manufacture
only differ in small details as indicated by these distinctions.

_Fine Wrappings._--The papers used for packing small goods such as
silver ware and other delicate articles are generally tissues, the
better qualities of which are made from rag, and the cheaper qualities
from wood pulp. These papers are known as tissue, crêpe, crinkled
tissue, manila tissue, and by a variety of trade terms.

[Illustration: FIG. 40.--Single Cylinder or Yankee Machine.]

Many of the fine wrappings of the tissue class and the somewhat heavier
papers known as M. G. Caps are manufactured on the single cylinder
machine, which produces a paper having a highly polished surface on one
side and a rough unglazed surface on the other side.

In the single cylinder machine the beaten pulp passes from the
stuff-chest on to the wire of the ordinary Fourdrinier machine and
through the press rolls, but instead of being dried over a number of
cylinders the paper is led over one single cylinder of very large
diameter which is heated internally with steam. The paper is usually
pressed against the surface of the cylinder by means of a heavy felt,
which is, however, sometimes omitted. The side of the paper coming
into contact with the cylinder becomes highly polished, the surface in
contact with the felt remaining in an unfinished rough condition. This
paper is said to be machine glazed and is known as an M. G. paper.

[Illustration: FIG. 41.--Section of Wet Press, or Board Machine.]

_Boards._--Cards, millboards, middles, boxboards, carriage panels,
and similar paper products are manufactured either on a _single board
machine_, by means of which single sheets of any required thickness can
be obtained, or on a _continuous board machine_, which is capable of
producing cards and plain or duplex boards of moderate thickness.

The raw material used consists, as in the case of browns and wrappers,
of every conceivable fibrous substance mixed with mineral matter and
then suitably coloured. The preliminary processes for the treatment of
the pulp are exactly the same as those employed in the case of brown
papers up to the point at which the beating has been effected.


SINGLE BOARD MACHINE.

The beaten pulp, diluted with large quantities of water, is pumped
continuously into a large wooden vat of rectangular shape. Inside
this vat revolves slowly a hollow cylindrical drum, the circumference
of which is covered with wire gauze of fine mesh. The drum is not
completely immersed in the mixture of pulp and water, so that as it
revolves the water passes through the wire, while the pulp adheres to
the surface. The water flows regularly into the interior of the drum
and runs away through pipes fitted at each side of the vat near the
axis of the drum, and the pulp is brought up out of the water until it
comes into contact with a travelling felt. The thin moist sheet of pulp
adheres to this felt, passes through squeezing rolls which remove part
of the water, and is finally carried between two wooden or iron rollers
of large diameter. The pulp adheres to, and is wound up on the upper
roller, the felt being carried back by the lower roller to the vat.
When the sheet on the upper roller has attained the desired thickness,
it is immediately cut off and transferred to a pile of similar sheets,
a piece of coarse sacking or canvas being interposed between every wet
board. The dimensions of the full-sized board are determined by the
diameter of the upper roller and its length. A roll 74 inches wide and
14 inches diameter will give a board 74 inches by 44 inches.

As soon as a sufficient number of wet boards has been obtained they are
submitted to pressure in order to remove the excess of water and at the
same time compress the material into dense heavy boards. The pieces of
sacking are then taken out and the boards dried by exposure to air at
the ordinary temperature or in a heated chamber.

[Illustration: FIG. 42.--Double Cylinder Board Machine.]

The dried boards are finished off by glazing rolls. These rolls
compress the boards still further and impart a polished surface. The
amount of "finish" may be varied by the pressure, number of rollings,
temperature of the rolls, and by damping the surface of the dry boards
just before they are glazed. The boards are cut to standard sizes
before or after glazing.

_Duplex Boards._--If the single board machine is fitted with two vats
instead of one, it is possible to manufacture a board with different
coloured surfaces. A board coloured red on one side and white on the
other is manufactured by having one vat full of pulp coloured red and
the second vat full of white pulp. The thin moist sheets from the two
vats are brought together and passed through the glazing rolls, which
cause the moist sheets to adhere closely to one another, the double
sheet of pulp so formed being wound up on the rollers at the end of the
machine. The board is then dried, glazed, and finished in the usual way.

The same principle is occasionally adopted on the Fourdrinier
machine for duplex wrappers. Thus a common brown pulp is worked up
in conjunction with a dyed pulp to produce a brown paper having one
surface of good paper suitably coloured. The brown pulp flows on to the
wire of the paper machine, and after it has been deprived of part of
the water at the suction boxes, a thin stream of coloured pulp, diluted
to a proper consistency, flows from a shallow trough, placed across and
above the wire, on to the wet brown web of paper in such a manner as to
completely cover it as a thin even sheet of coloured pulp. The adhesion
of the latter to the surface of the brown paper is practically perfect,
and the weight of the couch and press rolls ensures uniform felting of
the fibres.

_Middles._--This term is applied to a thin or thick cardboard made
of common material, the colour and appearance of which is of little
importance for inferior goods. Boards of this kind are covered
subsequently with papers of all colours and qualities, and the origin
of the word "middle" is easily seen. The manufacture of a board
consisting of two outside papers of good material and a middle produced
from common stuff is effected by the continuous boxboard machine,
unless the board is too thick to be passed over drying cylinders,
calendered, and reeled, in which case the boards are produced on an
ordinary wet machine and the paper pasted on the surface of the dry
board.

The term is, however, now also applied to a common paper made of
mechanical wood pulp with perhaps a little chemical pulp, used for
tram tickets, cheap advertising circulars, common calendar cards, and
similar purposes, to which no outer surface of a special character is
added.


CONTINUOUS BOARD MACHINE.

This machine differs from the single board machine in that the finished
board can be produced from the pulp at one operation. It is used
principally for cards and boards of moderate thickness which can be
wound up in the form of a reel at the end of the machine.

The mixture of pulp and water is pumped into two or more vats and
formed into a number of thin sheets, which are all brought together
between squeezing rolls and passed through heavy press rolls which
compress the several layers into a compact mass. The thick sheet
obtained is dried over steam-heated cylinders which are placed at the
end of the press rolls, and calendered. The whole process, indeed,
resembles that of ordinary paper-making, the main difference being the
method of producing the wet sheet or card.

Some machines are constructed with six or seven vats and forty to fifty
drying cylinders, and are capable of turning out a large quantity of
finished material.

The board can be made of uniform quality and texture throughout, or be
finished off with high-grade paper on one or both sides. In the latter
case the constituents of the "middle" part are waste papers and raw
material of inferior quality, the outer surface of wood pulp, white or
coloured according to circumstances. The variety of papers and boards
which can be produced is due to the fact that the several vats of pulp
are independent of one another and can be filled with any kind of paper
stock. The combined sheets forming the ultimate board are dried on
the ordinary cylinders, calendered, and reeled up at the end of the
machine.




CHAPTER VII

SPECIAL KINDS OF PAPER


There are many varieties of paper products obtained by submitting
finished paper to a number of special processes. Of these only a few of
the more important will be described.

These products can be divided approximately into three classes:--

(1) Papers coated on one side or both sides with various substances,
such as "art," photographic papers, etc.

(2) Papers impregnated with chemicals, such as blue print, medicated,
and cheque papers.

(3) Paper pulp converted into modified products by chemical treatment,
such as vulcanised board, viscoid, etc.

Of the first class, the coated papers used for art and chromo
illustrations are the most important.

Of the second class, the blue prints and papers impregnated with
chemicals, chiefly employed for the production of engineers' drawings,
may be regarded as typical.

In the third class, vegetable parchment and vulcanised board are the
most familiar.

       *       *       *       *       *

_Parchment Paper._--This is produced by the action of sulphuric acid
upon ordinary paper, the most suitable for this purpose being made
from unsized cotton rag, free from such additions as mechanical wood
pulp. The presence of the latter substance should be avoided, as it
is liable to char or burn, so that in the finished product it shows
itself in the form of small holes. The process depends upon the power
of sulphuric acid to change the surface of the paper into a gelatinous
mass, which has been shown to consist of a substance called amyloid.

The best parchment is made from pure cellulose such as rag or chemical
wood pulp. The quality of the parchment depends upon attention to the
strength of the acid, the temperature of the acid bath, the period of
immersion, the complete removal of the acid, and the careful drying of
the wet parchment.

[Illustration: FIG. 43.--Apparatus for making Parchment Paper.]

The acid is employed at a strength of 1·71 specific gravity, being
prepared by diluting the commercial concentrated acid in a leaden
vessel, with a sufficient quantity of water.

The parchment is generally prepared by passing a continuous sheet of
paper through a bath of acid of the proper strength at a speed which
ensures the correct period of immersion. As the treated paper leaves
the bath it passes through squeezing rolls which remove the excess of
acid, and the paper is then led through a series of tanks containing
fresh water, the last traces of acid being neutralised by small
additions of ammonia, or some alkali, to the last washing tank. The wet
parchment is then passed through suitable rollers and carefully dried
over cylinders heated internally by steam. The paper is kept perfectly
stretched as it dries, because it shrinks enormously, and would
otherwise become cockled and uneven.

Thick sheets of parchment paper are frequently made by passing three
sheets of paper through the acid bath and bringing them together
between the rollers before washing. The sheets unite when pressed
together; the remainder of the process being the same as that employed
for single sheets.

The parchment exhibits remarkable differences to the original paper,
the strength being increased three or four times, the density about 30
per cent., the latter being shown by the shrinkage, which amounts to at
least 30 per cent.

_Vulcanised Paper._--Zinc chloride has the property of parchmentising
paper in a manner similar to sulphuric acid. The product obtained when
this reagent is used is generally termed vulcanised fibre. The paper
is passed as a continuous sheet into a bath of strong zinc chloride,
having a density of 160-170 Twaddell, which causes the cellulose to
swell up and partly gelatinise. A very large excess of strong zinc
chloride is necessary, and the process is only rendered commercially
possible by careful recovery of the zinc from the washing waters, which
are submitted to chemical treatment.

The _vulcanised_ product is subsequently treated with nitric acid or
with a mixture of nitric and sulphuric acids to render them waterproof.
Dextrin is frequently employed to retard the chemical action to permit
of the necessary manipulation of the material before it is finally
washed. The complete removal of the excess of zinc and acid is a
necessary feature of the whole operation.

_Willesden Paper._--When paper is passed through an ammoniacal solution
of copper oxide, a superficial gelatinisation of the surface takes
place, so that the paper when washed and dried is impregnated with
copper oxide, which helps to preserve it, and it becomes waterproof.
Such material is well known as Willesden paper.

_Blue Print or Cyanotype Papers._--This name is usually given
to the process by means of which blue prints of engineers' and
architects' plans can be reproduced. It was discovered in 1842 by Sir
John Herschel. It is a useful method of reproducing drawings, and
incidentally is of great value to the amateur photographer because
of the facility with which it can be applied for getting proofs from
negatives quickly and easily without special baths and chemicals. The
process is based upon the reduction of a ferric salt to the ferrous
condition by light, and the formation of Prussian blue by the action of
potassium ferricyanide. The _negative cyanotype_ gives white lines on a
blue ground. Various formulæ are in common use.

  ----------------------------+---------+--------+--------+---------
                --            |Herschel.| Clark. | Watt.  |Rockwood.
  ----------------------------+---------+--------+--------+---------
                              |         |        |        |
  Solution 1.                 |         |        |        |
      Potassium ferricyanide  |    16   |   27   |   48   |    10
      Water                   |   100   |  100   |  100   |   100
      Ammonia                 |    --   |  2·3   |   --   |    --
      Saturated solution of   |         |        |        |
        oxalic acid           |    --   |   20   |   --   |    --
  ----------------------------+---------+--------+--------+---------
                              |         |        |        |
  Solution 2.                 |         |        |        |
      Ammonia-citrate of iron |    20   |   30   |   50   |    30
      Water                   |   100   |  100   |  100   |   100
      Boric acid              |    --   |   --   |  0·5   |    --
      Dextrin                 |    --   |   --   |   --   |     5
  ----------------------------+---------+--------+--------+---------

Equal parts of the two prepared solutions are mixed when required and
spread evenly over well-sized paper. The paper is hung up, dried, and
preserved in a dark dry place.

The _positive cyanotype_ gives blue lines on a white ground, being the
reverse of the ordinary blue print. That is, no image is formed where
the light acts, and the reaction is the formation of blue due to the
union of a ferrous salt with ferrocyanide of potassium.

Pizzighelli in 1881 gave the following formula:--

  -----------------------+-----------+-----------+-----------+-----------
             --          |Solution 1.|Solution 2.|Solution 3.|Solution 4.
  -----------------------+-----------+-----------+-----------+-----------
  Water                  |    100    |    100    |    100    |    100
  Gum arabic             |     20    |     --    |     --    |     --
  Ammonia-citrate of iron|     --    |     50    |     --    |     --
  Ferric chloride        |     --    |     --    |     50    |     --
  Potassium ferrocyanide |     --    |     --    |     --    |     20
  -----------------------+-----------+-----------+-----------+-----------

Mix the first three solutions in the following order in the proportions
stated:--

                  Solution 1.   20 parts.
                  Solution 2.    8   "
                  Solution 3.    5   "

As soon as the solution, which at first gets thick and cloudy, is clear
and thin, it is spread over the surface of well-sized paper, which is
then dried in a warm room.

The print, which appears yellow on a dark yellow ground, is treated
with the developer (solution 4) by means of a brush dipped in the
solution. When the image is deep blue in colour, the print is washed in
water and then placed in dilute hydrochloric acid (1 part of acid to 10
parts of water) till the ground is quite white. A final washing with
water is then necessary.

Waterhouse gives the following formula:--

  ---------------------+-----------+-----------+-----------+-----------
            --         |Solution 1.|Solution 2.|Solution 3.|Solution 4.
  ---------------------+-----------+-----------+-----------+-----------
  Water                |    650    |    150    |     --    |    100
  Gum arabic           |    170    |     --    |     --    |     --
  Tartaric acid        |     --    |     40    |     --    |     --
  Ferric chloride      |           |           |           |
    solution 45° Baumé |     --    |     --    |    150    |     --
  Ferrocyanide of      |     --    |     --    |     --    |     20
    potassium          |           |           |           |
  ---------------------+-----------+-----------+-----------+-----------

Solutions 1 and 2 are mixed and No. 3 added gradually with constant
stirring. The mixture is left twenty-four hours, and diluted with water
to a specific gravity of 1·100.

The paper is coated with the solution and used as already directed,
being developed in ferrocyanide of potassium solution and washed with
water, treated with weak hydrochloric acid, and then finally cleaned
from all traces of acid.

_Black Lines on a White Ground._--This modification of the ordinary
blue print is arrived at with the following formula:--

  Water                                          96·0 parts.
  Gelatine                                        1·5   "
  Perchloride of iron (in syrupy condition)       6·0   "
  Tartaric acid                                   6·0   "
  Sulphate of iron                                1·5   "

The paper is coated with the solution. After printing, the image is
developed with a solution containing

            Gallic acid                     1 part.
            Alcohol                        10 parts.
            Water                          50   "

A final washing of the print with water completes the operation.


COATED PAPERS.

This term should properly include all the varieties of special papers
which are coated with extraneous matter for particular purposes, such
as art, chromo, tinfoil, gilt, emery, carbon, photographic, marble, and
sand papers. In practice however, the term is almost entirely limited
to "art" papers used for illustration work and half-tone printing.

An "art" paper, using the definition given above, consists of an
ordinary sheet of paper, one or both sides of which have been coated
by the application of a mixture of a mineral matter, such as china clay
or satin white, and some adhesive, like casein or glue. The object
of the coating is to impart to the paper a perfectly smooth surface,
rendered necessary because of the conditions under which the printing
of the illustrations is carried out.

[Illustration: FIG. 44.--General arrangement of Plant for making "Art"
Paper.]

The machine used for coating the paper consists of a large hollow drum
about 40 inches diameter and 48 inches wide. The paper is brought over
upon the drum in a continuous sheet, and the coating mixture applied
to the surface by means of a revolving brush or an endless felt which
rotates in a copper trough containing a coating mixture which is
usually maintained at a temperature of 120° Fahr.

The amount of material put on to the surface of the paper is varied by
altering the proportion of water in the trough. As the wet coated paper
is drawn over the drum it comes into contact with a number of flat
brushes which move from side to side and brush the coating well into
the paper.

[Illustration: FIG. 45.--Sectional Elevation of "Coating" Plant.]

The last two or three brushes on the drum are made of very fine
bristles, so that when the coated paper leaves the machine the surface
is perfectly even and free from brush marks. The wet paper is then
drawn up an inclined ladder by an ingenious device, which causes the
paper to fall into festoons or loops, and these are carried bodily
forward by means of travelling chains. The process, somewhat difficult
to describe, is more easily understood by a study of the illustrations
given.

The paper is dried by a current of warm air which can be obtained by
means of steam pipes placed below the festoons or with a special air
blower. The dry paper is then led through guide rolls and wound up in
the form of a reel.

The paper at this stage has a dull coated surface, which is somewhat
rough and unfinished, and a high polish is imparted to it by a machine
known as a supercalender.

The supercalender consists of a number of alternate steel and cotton or
paper rolls placed vertically in a stack one above the other. When the
coated paper is led through this machine the friction of the alternate
steel and cotton rolls produces a high finish on its surface.

An art paper coated on both sides is manufactured by passing the paper
through the coating machine twice. Machines have been devised for
coating both sides of the paper at one operation, but these are not in
very general use.

Tinted art papers are prepared in the same manner, the desired colour
being obtained by the addition of pigments or aniline dyes to the
mixture in the trough containing the coating materials. When the two
sides of such tinted papers are coloured differently, they are often
described as duplex coated papers.

_Imitation Art Papers_ are prepared by quite a different process,
although they have the appearance, more or less, of the coated paper.
They are merely esparto papers very heavily loaded, containing
frequently as much as 25 to 30 per cent. of mineral matter prepared as
follows:--

Bleached esparto half-stuff is beaten together with any suitable
proportion of chemical wood pulp in an ordinary beating engine, and a
large quantity of china clay is added at the same time. The beating
is carried out under conditions which favour the retention of as much
china clay as the pulp will hold while being converted into paper on
the Fourdrinier machine.

After the paper passes over the drying cylinders of the machine it is
passed through the calenders in the usual way, but the surface of the
paper is damped by means of a fine water spray just before it enters
the calender rolls. The result is that a "water-finish," so called, is
imparted to the paper, and a close imitation of the genuine art paper
is obtained, the effect of this peculiar treatment being to compress
the fibres and bring the clay up, as it were, to the surface.

A paper containing such a large proportion of mineral matter intimately
mixed with the fibre is naturally very weak. It easily tears, and if
moistened with water goes all to pieces. At the same time it is a cheap
substitute for high-class art paper, being suitable for circulars,
temporary catalogues, and similar printed matter.

In an "art" paper the nature of the fibrous constituents is too often
regarded as a matter of secondary importance, because in the process
of printing the ink does not come into contact at all with the paper,
and an impression is produced merely on a layer of clay which is bound
together by the glue.

The illustrations are not absolutely permanent, and it is perfectly
easy to remove the whole of the impression and the coating itself by
immersing a sheet of the paper in warm water and rubbing the surface
gently with the fingers, or with a camel-hair brush.

In fact the amount of coating matter which has been brushed on to
a paper can be determined approximately by weighing a piece of the
coated paper, removing the mineral matter and glue from both sides as
indicated, allowing the paper to dry again, and then re-weighing, the
loss in weight representing the amount of coating.

It is not surprising to find that the true paper is merely regarded as
a convenient means of producing, so to speak, a smooth surface of clay,
and an examination of the material between the two clay surfaces often
reveals a paper of very low quality.

There are one or two empirical methods for testing the condition of
coating on an art paper. If the coating is firm and adherent, then on
pressing the moistened thumb on to the surface none of the coating
matter is removed, but in a badly-made art paper some of the coating
adheres to the thumb.

Another method is to crumple a sheet of paper between the fingers, and
if any of the coating comes away easily the paper is considered of poor
quality.

The complete examination of an art paper, apart from the practical test
of printing, involves the determination of the amount of coating matter
added to the paper, the proportion of glue in the coating, and the
usual analysis of the paper itself.


PACKING PAPERS.

This term may be applied to wrappings specially treated with substances
which render the paper air and water proof. They are principally used
for preserving food, or such articles as tobacco, which require to be
kept slightly moist.

_Waxed Paper._--The paper in the form of a continuous sheet is passed
through a bath of melted wax at a high temperature, any excess being
removed by squeezing rolls through which the hot waxed paper is passed.
The paper is led over skeleton drums and thoroughly cooled before being
cut into sheets.

_Butter Paper._--Ordinary parchment paper is generally used, but
for special purposes a solution containing albumen and saltpetre is
utilised for impregnating paper.

_Hardware Paper._--Needles and silver goods are frequently wrapped
in paper impregnated or mixed with substances which are supposed to
prevent deleterious fumes from coming into contact with them. The use
of black papers heavily loaded with pigment, sized with glue and an
excess of alum, is commonly resorted to. For silver ware, paper dipped
in a solution of caustic soda containing zinc oxide is used. A recent
patent suggests the impregnation of paper with heavy hydrocarbon oils,
which being slightly volatile cover the goods, such as needles, with a
thin film.

_Paraffin Paper._--Large quantities of this paper are consumed for
packing food and other articles which need protection from air and
moisture.

The paper is either passed through a bath of paraffin or passed over a
roller which rotates in a trough of paraffin.

If the paper is to be coated on both sides it is passed through the
bath containing the paraffin in a melted condition, the excess of which
is scraped from the paper as it leaves the bath. The paper is cooled by
exposure to air, and when the paraffin has solidified upon the sheet
the paper is wound up on a roller at the end of the machine.

If the paper is to be coated on one side only it is passed over a
heated roller which revolves in a bath of melted paraffin, the other
operations of drying and finishing being the same as in the case of a
paper coated on both sides.

_Tinfoil Papers_, required for packing tea, coffee, and similar
foodstuffs, are prepared by coating cheap paper with a solution of
gum and finely powdered tin. The manufacture of the fine powder
is accomplished by melting tin at a low temperature and shaking
it continually as it cools down, whereby a mixture of fine powder
and large particles is produced, the latter being separated out by
agitation of water.

Tin in a fine state of division can also be obtained by a chemical
process. Granulated tin is dissolved in strong hydrochloric acid, the
solution diluted with water, and a stick of zinc introduced into the
solution. The tin is gradually precipitated.

The dried powder is coated on to the paper with gum, and when the
paper is dry the necessary degree of brilliancy produced by suitable
calendering.

_Transfer Papers._--A number of important operations require the use
of what are known as _transfer_ papers, so that a design written or
printed upon a specially prepared surface can be _transferred_ to
another surface from which duplicate copies may be obtained. The
principle upon which all such operations are based is the coating of
suitable paper with starch, flour, and gum, singly or mixed, so as to
give a surface firm enough to take the design, but which readily breaks
up when the printed side is pressed against the wood, stone, or metal
object intended to receive the design.

Thus a paper may first be dusted over with dry starch, or coated with
starch paste and then dried. A layer of dextrine may then be put over
the starch coating, and the design printed upon the dextrine surface.
When the paper is turned face downward on a sticky metal plate the
design adheres to the metal, and the paper is easily pulled off, owing
to the dry starch layer between it and the dextrine being non-adhesive.

This principle is utilised in producing designs upon tins used for
packing, metal advertisement plates, domestic articles of every kind,
stoneware and earthenware goods.

It is further applied in the preparation of lithographic stones
required for printing.

Each class of work demands paper of a suitable character, but the
principle of an easily detached surface-coating is the same for all.
The main difficulty experienced is the liability of paper to stretch
when damped, and various methods are devised to obviate this, either by
employing paper which stretches very little when damp, or by making the
paper partially waterproof before use.

_Papier-mâché._--This name indicates a preparation of paper or paper
pulp mixed with various mineral substances firmly cemented together by
animal or vegetable adhesives.

The _paper pulp_ used for high-class goods consists of pure wood
cellulose, while for the commoner qualities mechanical wood pulp, waste
papers, and any similar fibrous material are employed.

The _mineral_ substances used are china clay, chalk, gypsum, barytes,
ochre, sienna, and other mineral pigments.

The _adhesive_ materials are glue, casein, gum, starch, paste,
dextrine, Iceland moss, or wax.

For experimental purposes, small quantities of papier-mâché may be
prepared in the following manner:--

When old newspapers or brown papers are used as the fibrous basis of
the papier-mâché, they are first torn up into small pieces, moistened
with hot water, tied up in a small cloth bag or sack, which must
only be half filled, and then immersed in a basin of warm water and
thoroughly kneaded by hand, so that the paper is gradually reduced
to the condition of pulp. If the kneading process is carried out
thoroughly the paper is entirely reduced to pulp. The excess of water
can be removed by pressure and the preparation of the final mixture
completed by the incorporation of clay, pigment, and adhesive.

In the preparation of papier-mâché for goods on a large scale a beating
engine is used in order to break up the old paper or wood pulp into a
fibrous condition.

The following formulæ can be used for making papier-mâché:--

  -----------+-----------+---------------+-----------
      (1)    |    (2)    |     (3)       |    (4)
  -----------+-----------+---------------+-----------
  Pulp    22 | Pulp   22 | Pulp       12 | Pulp    33
  Clay    37 | Chalk  30 | Rosin size 22 | Starch   9
  Casein  37 | Glue    4 | Flour      11 | Clay     9
  Water    4 | Water  44 | China clay 11 | Water   49
             |           | Water      44 |
         --- |       --- |           --- |        ---
         100 |       100 |           100 |        100
  -----------+-----------+---------------+-----------

_Plaster Moulds._--Plaster of Paris or gypsum is the main article used
for moulds and pattern. The preparation of gypsum for casting is made
as follows:--The gypsum is gradually worked up into a creamy paste with
water, the mixing being done quickly yet thoroughly.

The pattern of which it is desired to form a mould must be coated with
oil. Around the pattern placed on a table a wall of wood or pasteboard
is fixed, so that a basin will be formed of suitable depth, preventing
the gypsum from flowing away. Patterns of figures or of curved articles
have to be made in two or more parts. For that purpose the pattern is
usually cut into two pieces. Two moulds are now readily obtainable by
first oiling the pattern and by pouring the gypsum in a thin state
gradually over the surface, to avoid the forming of air bubbles.

The rapid drying of the soaked gypsum is sometimes inconvenient, but
the addition of a saturated solution of borax in water to the gypsum
mixture can be resorted to as a check.

Various means are employed for hardening and strengthening the plaster
cast, such as the addition of coarse paper fibres, shreds of canvas,
iron filings, or wire.

_Colouring._--Usually a cheap water colour only is required; a light
coating of a cheap varnish may be sufficient. In other cases a water
colour serving as a filler for smoothing the surface may receive a
finish of one or more coats of resinous solutions in alcohol or of
copal varnish. Many goods are coated with asphaltum or Japan varnish
and dried in cold or hot air.

Some of the articles may be decorated with scrolls or arabesques in oil
colours or enamels, or the lines may be covered with bronze powder, or
with metal, gold, or aluminium leaf.

_Varnishing._--The following varnish recipes are suitable:--

  --------------+---------------+--------------+-------------
       (1)      |     (2)       |     (3)      |     (4)
  --------------+---------------+--------------+-------------
  Shellac    20 | Shellac    10 | Shellac    6 | Sandarac  15
  Alcohol    70 | Rosin      10 | Sandarac   3 | Mastic     5
  Lamp black 10 | Alcohol    60 | Mastic    18 | Turpentine 5
                | Lamp black 20 | Alcohol   73 | Alcohol   75
            --- |           --- |          --- |          ---
            100 |           100 |          100 |          100
  --------------+---------------+--------------+-------------




CHAPTER VIII

CHEMICALS USED IN PAPER-MAKING


The manufacture of paper is a highly technical industry, which requires
a practical knowledge of mechanical engineering, as well as an intimate
acquaintance with the many important chemical problems connected with
the art.

The following brief description of the various chemicals used in the
manufacture of paper is divided into certain classes, based upon the
order of the operations through which the raw material passes before
its final conversion into paper:--

(1) The alkaline processes used for treating raw fibre: soda ash;
caustic soda; lime; recovered ash.

(2) The conversion of wood into sulphite pulp: sulphur; limestone.

(3) The operation of bleaching: bleaching powder; antichlors; acids.

(4) The sizing and loading of paper: casein; gelatine; rosin size;
alum; starch; silicate of soda; pigments and soluble dyes; mordants.

Mineral substances for loading: clay, blanc fixe, etc.

_Carbonate of Soda._--This substance, also known under the trade names
of alkali and soda ash, is used in the paper mill for the manufacture
of caustic soda. It is purchased by the paper-maker from the chemical
works, and used together with the recovered ash (see page 78) for the
production of caustic soda solution, which is required in the treatment
of raw fibres.

It is also used for the preparation of rosin size (see "Rosin Size")
and in softening hard waters for steam-raising purposes.


SODIUM CARBONATE TABLE.

Showing percentage by weight and pounds per 100 gallons in solutions of
various densities.

  ---------+-----------------------+-----------------------------------
           | Percentage by Weight. |   100 gallons contain pounds of
  Twaddell.+-----------------------+---------+-------------+-----------
           | Na_{2}O.|Na_{2}CO_{3}.| Na_{2}O.|Na_{2}CO_{3}.| 48 per
           |         |             |         |             |cent. Ash.
  ---------+---------+-------------+---------+-------------+-----------
      1    |   0·28  |      0·47   |   2·76  |      4·72   |    5·74
      2    |   0·56  |      0·95   |   5·61  |      9·60   |   11·68
      3    |   0·84  |      1·42   |   8·42  |     14·41   |   17·56
      4    |   1·11  |      1·90   |  11·34  |     19·38   |   23·64
      5    |   1·39  |      2·38   |  14·26  |     24·40   |   29·73
      6    |   1·67  |      2·85   |  17·10  |     29·36   |   35·77
      7    |   1·95  |      3·33   |  20·16  |     34·46   |   42·00
      8    |   2·22  |      3·80   |  23·12  |     39·52   |   48·15
      9    |   2·50  |      4·28   |  26·17  |     44·72   |   54·50
     10    |   2·78  |      4·76   |  29·71  |     50·00   |   60·90
     11    |   3·06  |      5·23   |  32·27  |     55·18   |   67·22
     12    |   3·34  |      5·71   |  35·36  |     60·50   |   73·72
     13    |   3·61  |      6·17   |  38·43  |     65·72   |   80·07
     14    |   3·88  |      6·64   |  41·57  |     71·06   |   86·58
     15    |   4·16  |      7·10   |  44·65  |     76·33   |   93·03
     16    |   4·42  |      7·57   |  47·80  |     81·77   |   99·61
     17    |   4·70  |      8·04   |  51·02  |     87·24   |  106·31
     18    |   4·97  |      8·51   |  54·25  |     92·74   |  113·10
     19    |   5·24  |      8·97   |  57·45  |     98·26   |  119·70
     20    |   5·52  |      9·43   |  60·67  |    103·70   |  126·42
     21    |   5·79  |      9·90   |  63·98  |    109·40   |  133·45
     22    |   6·06  |     10·37   |  67·32  |    115·10   |  140·12
     23    |   6·33  |     10·83   |  70·63  |    120·81   |  147·10
     24    |   6·61  |     11·30   |  74·00  |    126·62   |  154·20
     25    |   6·88  |     11·76   |  77·38  |    132·30   |  161·12
     26    |   7·15  |     12·23   |  80·83  |    138·20   |  168·51
     27    |   7·42  |     12·70   |  84·31  |    144·12   |  175·70
     28    |   7·70  |     13·16   |  87·67  |    150·20   |  182·70
     29    |   7·97  |     13·63   |  91·28  |    156·15   |  190·14
     30    |   8·24  |     14·09   |  94·77  |    162·00   |  197·40
  ---------+---------+-------------+---------+-------------+-----------

_Analysis._--The value of soda ash, carbonate of soda, and recovered
ash depends on the amount of available alkali (Na_{2}O) present.

A weighed quantity (15·5 grammes conveniently) is dissolved in a
measured volume of distilled water (500 c.c.), and titrated with
standard normal hydrochloric acid, methyl orange indicator being used.

_Caustic Soda._--Raw vegetable fibres may be reduced to the condition
of paper pulp by treatment with caustic soda. In practice this process
is largely resorted to for the manufacture of pulp from esparto, straw,
and wood, the spent caustic soda being recovered and used again.

The paper-maker prepares the caustic required for digesting the raw
material from recovered ash and carbonate of soda.

A convenient volume of clear liquor obtained by lixiviating the
recovered ash is boiled with lime in suitable causticising pans, the
reaction being represented as follows:--

  Na_{2}CO_{3} + CaO  + H_{2}O = 2 NaOH       + CaCO_{3}.
  Soda ash     + Lime + Water  = Caustic soda + Chalk.

According to this equation, 100 lbs. of soda ash require 53 lbs. of
quicklime, but a slight excess is generally added, 58 or 60 lbs. being
the usual amount actually employed. Several precautions should be
observed in the process of causticising.

(1) The liquor from the recovered soda should be bright and clear,
indicating complete incineration of the ash.

(2) The liquor is best causticised at a density between 1·050 and 1·100
(10-20, Twaddell). With stronger solutions the reaction is complicated
and the yield of caustic soda reduced. Lunge has shown that if the
density of the solution is 1·025 the proportion of soda causticised is
99·5 per cent., whereas at a density of 1·150 it is only 94·5 per cent.
In the latter case the caustic soda formed acts upon the chalk produced
and is reconverted into carbonate.

(3) The large quantities of chalk residue resulting from the reaction
must be thoroughly and carefully washed. The economy of the whole
process depends in no small measure upon this seemingly small detail.


CAUSTIC SODA TABLES.

  Showing quantity of liquor obtained from 1 cwt. of caustic soda and
      the amount of caustic soda in 100 gallons of liquor (adapted from
      Lunge and others).

  ---------+--------------------------++---------+-------------------------
           |  Gallons obtained per    ||         | Pounds of Caustic Soda
           |      hundredweight       ||         | per 100 gallons Liquor.
           |        of Caustic.       ||         |
  Twaddell.+------------+-------------++Twaddell.+------------+------------
           |60 per cent.|77 per cent. ||         |60 per cent.|77 per cent.
           |Caustic.    |Caustic      ||         |Caustic.    |Caustic
           |            |Pure.        ||         |            |Pure.
  ---------+------------+-------------++---------+------------+------------
       1   |    1,777   |    2,358    ||    1    |    6·3     |    4·75
       2   |      896   |    1,179    ||    2    |   12·5     |    9·5
       3   |      596   |      767    ||    3    |   18·8     |   14·6
       4   |      448   |      574    ||    4    |   25·0     |   19·5
       5   |      359   |      457    ||    5    |   31·2     |   24·5
       6   |      298   |      384    ||    6    |   37·6     |   29·2
       7   |      256   |      330    ||    7    |   43·8     |   34·0
       8   |      223   |      287    ||    8    |   50·1     |   39·0
       9   |      199   |      256    ||    9    |   56·2     |   43·7
      10   |      178   |      229    ||   10    |   62·9     |   48·9
      11   |      162   |      208    ||   11    |   69·1     |   53·7
      12   |      148   |      190    ||   12    |   75·7     |   58·7
      13   |      136   |      176    ||   13    |   82·1     |   63·7
      14   |      126   |      166    ||   14    |   88·5     |   67·5
      15   |      117·5 |      152    ||   15    |   95·0     |   73·5
      16   |      110   |      141·5  ||   16    |  101·5     |   79·0
      17   |      103·5 |      135    ||   17    |  107·8     |   83·0
      18   |       98   |      125·5  ||   18    |  114·4     |   89·0
      19   |       92·8 |      119·5  ||   19    |  120·8     |   93·8
      20   |       88   |      114    ||   20    |  127·2     |   98·0
      25   |       70   |       90·3  ||   25    |  159·5     |  124·0
      30   |       56·5 |       73    ||   30    |  197·3     |  153·0
      35   |       48   |       61·5  ||   35    |  234·9     |  182·2
      40   |       41   |       53    ||   40    |  272·6     |  211·6
      45   |       35·3 |       45·5  ||   45    |  317·4     |  246·3
      50   |       31   |       40    ||   50    |  362·1     |  281·0
  ---------+------------+-------------++---------+------------+------------


DILUTION TABLE FOR STRONG LIQUORS.

  Showing number of gallons of water required to reduce the density
      of 100 gallons of liquor from a higher density, D, to a lower
      density, _d._ (See page 163).

  -----------+---------------------------------------------------------
  Higher     |     Lower Density, _d._
  Density, D +-----+-----+-----+-----+---+-----+---+-----+-----+---+---
  (Twaddell).| 14. | 13. | 12. | 11. |10.|  9. | 8.|  7. |  6. | 5.| 4.
  -----------+-----+-----+-----+-----+---+-----+---+-----+-----+---+---
       42    |200  |223  |250  |281·8|320|367  |425|500  |600  |740|950
       40    |185  |207  |233·3|263·6|300|344·4|400|471·4|566·6|700|900
       38    |171  |192  |216·6|245·5|280|322·2|375|442·8|533·3|660|850
       36    |157  |177  |200  |227·3|260|300  |350|414·3|500  |620|800
       34    |143  |161·5|183·3|209·1|240|277·7|325|385·7|466·6|580|750
       32    |128·6|146  |166·6|191  |220|255·5|300|357·1|433·3|540|700
       30    |114·3|130·6|150  |172·8|200|233·3|275|328·5|400  |500|650
       28    |100  |115·3|133·3|154·6|180|211·1|250|300  |366·6|460|600
       26    | 85·7|100  |116·6|136·4|160|188·8|225|271·4|333·3|420|550
       24    | 71·4| 84·6|100  |118·2|140|166·6|200|243  |300  |380|500
       22    | 57·1| 69·2| 83·3|100  |120|144·4|175|214·4|266·6|340|450
       20    | 43  | 53·6| 66·6| 81·8|100|122·2|150|185·7|233·3|300|400
       18    | 28·6| 38·4| 50  | 63·7| 80|100  |125|157  |200  |260|350
       16    | 14·3| 23  | 33·3| 45·5| 60| 77·7|100|128·5|166·6|220|300
  -----------+-----+-----+-----+-----+---+-----+---+-----+-----+---+---

_Lime and Limestone._--Carbonate of soda and recovered ash are
converted into caustic soda by means of lime. About sixty parts of
lime are necessary for the conversion of 100 parts of carbonate of
soda. Large quantities of insoluble carbonate of lime are produced
in this operation, and great care is necessary to prevent a loss of
caustic soda which occurs if the residue is not thoroughly washed. In
some cases the residual chalk is drained by vacuum filters in order to
remove all traces of soluble alkali. Processes have been devised for
calcining the residue so as to convert the carbonate into caustic lime
to be used over again, but no economical and practical method has yet
been found. The treatment of the residual chalk with sulphuric acid for
the production of calcium sulphate appears feasible, but the substance
obtained is very impure, and therefore has little commercial value.

Limestone is required in considerable quantity for the preparation of
sulphite of lime for the manufacture of wood pulp.

_Recovered Ash._--The black liquor obtained during the process of the
boiling of straw, esparto, and other paper-making fibres contains a
large proportion of non-fibrous organic constituents derived from the
fibres, the quantity of which may be gauged from the fact that these
fibres generally lose 50 per cent. of their weight when being boiled.
The black liquor on evaporation yields a thick resinous mass, which is
converted into carbonate of soda when burnt.

Advantage is taken of this fact to carry out a process of incineration
on a large scale, so that heat derived from the burning off of the
resinous mass is utilised for evaporation of weaker liquors. The ash is
drawn from special furnaces, put aside, and allowed to char quietly, so
that the carbonaceous matter is more or less completely burnt away. The
ash in this form contains about 40 per cent. of soda, its composition
being determined by the nature of the fibre which has been treated. In
the case of straw, the amount of silicate is considerable, as shown by
the following typical analysis:--

    Sodium carbonate                     70·2
    Sodium hydrate                        2·3
    Sodium sulphate                       4·1
    Sodium chloride                       7·5
    Silica                                7·5
    Oxides of iron and alumina            0·75
    Unburnt carbon, etc.                  7·65
                                        ------
                                        100·00
                                        ------

At the present time there is no process in general use for the recovery
of the liquors used in the treatment of wood by the sulphite process.
Many schemes have been proposed, the most promising of which is that of
Drewsen.

_Sulphur and Sulphites._--The pale yellow brittle substance known as
sulphur is too familiar to require any detailed description. It unites
with oxygen in various proportions, and these in contact with water
form the various sulphur acids known to commerce. Sulphur burned with a
limited quantity of air forms sulphurous acid gas, and this substance
is the chief product of oxidation, which by further treatment can be
converted into sulphites.

In the manufacture of the sulphur compounds required in the preparation
of wood pulp, the furnace for burning the sulphur consists of a
flat-bottomed cast iron retort which is very shallow, and provided with
a curved top, to which a pipe is fixed, so that the sulphurous acid may
be conveyed away from the furnace. In the most recent form of sulphur
oven a small conical-shaped revolving furnace is employed, which
produces a satisfactory gas of constant composition very economically.

_Bisulphite of Lime._--This compound is obtained when the sulphurous
acid gas is brought into contact with moistened limestone. In the
manufacture of bisulphite of lime on a large scale the sulphurous acid
gas is drawn or pumped up tall circular towers filled with blocks of
limestone, kept moistened by a carefully regulated stream of water
flowing from the top of the tower.

In another system known as the acid tank process, the gas is forced
into large circular vats containing milk of lime.

In either case a solution is prepared containing bisulphite of lime,
together with a certain proportion of free sulphurous acid, the object
of the pulp manufacturer being to obtain a solution containing as large
a proportion of free sulphurous acid as possible. The composition of a
solution will vary on this account, and the following may be quoted as
being an example of such a liquor:--

    Free sulphurous acid                 3·23 per cent.
    Combined sulphurous acid             0·77  "    "
                                         ----
                                         4·00  "    "
                                         ----

For experimental purposes the bisulphite of lime solution may be
prepared by passing sulphurous acid gas into a mixture of water and
sulphite of lime. The latter compound is insoluble in water, but
gradually dissolves when the gas is absorbed. A known weight of
sulphite of lime is added to a measured volume of water, and the
sulphurous acid gas discharged into the mixture from a siphon of
compressed sulphurous acid. The amount of gas absorbed is determined
by weighing the siphon before and after use, the loss of weight
representing the gas discharged.

The following figures may be quoted as an example:--

                                  Quantities used.
    Calcium sulphite                     536 grammes.
    Water                               7100 c.c.
    Gas absorbed                         534 grammes.
    Density of solution                  18° Twaddell.

The composition of the solution prepared is--

    Combined sulphurous acid                   3·50
    Free sulphurous acid                       6·54
    Lime                                       3·06
    Water                                     86·90
                                             ------
                                             100·00
                                             ------

_Analysis._--The examination of sulphite liquors for free and combined
sulphurous acid is made by means of standard iodine solution and normal
caustic soda solution.

A known volume of the sulphite liquor is first titrated with standard
iodine solution, the number of cubic centimetres required being a
measure of the total sulphurous acid.

Each cubic centimetre standard iodine solution = ·0032 grammes SO_{2}.
The titrated liquor is then treated with standard caustic soda in
quantity sufficient to exactly neutralise the acid. The volume of
caustic soda solution used minus the number of cubic centimetres of
iodine first added is a measure of the free sulphurous acid.

_Bleaching Powder._--This substance is prepared on a large scale by
allowing chlorine gas to act upon dry slaked lime. The lime absorbs
nearly one-half its weight of chlorine and forms a dry white powder,
having a very pungent odour. The best bleaching powder contains about
37 per cent. of what is termed "available chlorine." The substance,
on being treated with water, gives a greenish-coloured solution known
as bleach liquor, and when raw paper-making material, after having
been digested with caustic soda, is treated with this solution, it is
gradually bleached to a white colour. The composition of the powder may
be represented approximately as follows:--

    Available chlorine (combined with lime)      36·00
    Chlorine in the form of chloride              0·32
    Chlorine in the form of chlorate              0·26
    Lime                                         44·66
    Magnesia                                      0·43
    Silica, iron oxides, etc.                     1·33
    Insoluble matter                             17·00
                                                ------
                                                100·00
                                                ------

Since the amount of bleach used for wood pulps varies from 8 per cent.
to 25 per cent. of powder on the dry wood pulp, the cost of bleaching
in some cases is considerable. The economy of the process depends in
some measure upon the care exercised in the purchase of bleaching
powder of standard quality, the storage of same in a dark, cool place,
and the efficient treatment or exhaustion of the powder when the bleach
liquor is prepared.

The powder is usually agitated for about an hour with water sufficient
to produce a liquor of 13°-15° Twaddell. The undissolved powder is
allowed to settle and the clear solution siphoned off, after which
the sediment is washed once or twice to remove all the soluble matter
completely.


BLEACH LIQUOR TABLE.

  Showing for bleaching powder solutions of known density the quantity
      of powder necessary to produce 100 gallons of liquor and the
      number of gallons obtained from 1 cwt. of powder (adapted from
      Lunge and Beichofen).

  ---------+----------+--------------------------+-------------------------
           |Available |Number of Gallons obtained|Pounds of Powder per 100
           |Chlorine  |from 112 lbs. of Powder.  |gallons of Liquor.
  Twaddell.|Pounds    +------------+-------------+------------+------------
           |per 100   |34 per cent.|35 per cent. |34 per cent.|35 per cent.
           |gallons.  |  Powder.   |  Powder.    |  Powder.   |  Powder.
  ---------+----------+------------+-------------+------------+------------
     0·25  |    0·70  |    5,464   |    5,600    |    2·05    |    2·00
     0·50  |    1·40  |    2,725   |    2,800    |    4·11    |    4·00
     1     |    2·71  |    1,405   |    1,445    |    7·97    |    7·74
     2     |    5·58  |      681   |      702    |   16·41    |   15·94
     3     |    8·48  |      448   |      462    |   24·95    |   24·23
     4     |   11·41  |      334   |      340    |   33·55    |   32·60
     5     |   14·47  |      264   |      270    |   42·58    |   41·34
     6     |   17·36  |      219·5 |      225    |   51·06    |   49·60
     7     |   20·44  |      186   |      191    |   60·11    |   58·40
     8     |   23·75  |      160   |      165    |   69·85    |   67·85
     9     |   26·62  |      141   |      147    |   78·30    |   76·57
    10     |   29·60  |      129   |      132·5  |   87·06    |   84·54
    11     |   32·68  |      116·5 |      120    |   96·11    |   93·37
    12     |   35·81  |      106·5 |      109·5  |  105·32    |  102·31
    13     |   39·10  |       98   |      100    |  115·00    |  111·70
    14     |   42·31  |       90   |       92·5  |  124·45    |  120·90
    15     |   45·70  |       84   |       86    |  134·41    |  130·56
    16     |   48·96  |       78   |       80    |  143·80    |  139·71
    17     |   52·27  |       73·5 |       75    |  153·53    |  149·34
    18     |   55·18  |       69   |       71    |  162·30    |  157·65
    19     |   58·40  |       65·5 |       67    |  171·00    |  166·86
    20     |   61·50  |       61·5 |       64    |  180·88    |  175·71
  ---------+----------+------------+-------------+------------+------------

The best method for extracting powder is to agitate the material with
water for a short period, and to stop the mixing process directly the
maximum density has been obtained, which usually takes place in 15
minutes. Prolonged agitating prevents the powder from settling readily.

The maximum quantities of liquor which can be obtained from bleaching
powder are shown on page 162. The following table is useful as showing
the amount of water required for diluting strong liquors, the figures
being applicable to any solution independent of the nature of the
dissolved substance.


DILUTION TABLE FOR WEAK LIQUORS.

  Showing number of gallons of water required to reduce the density
      of 100 gallons of liquor from a higher density, D, to a lower
      density, _d_. (See page 157.)

  -----------+------------------------------------------------------------
    Higher   |                     Lower Density, _d._
  Density, D +----+----+---+----+-----+-----+-----+---+---+-----+---+-----
  (Twaddell).| 12.| 11.|10.| 9. |  8. |  7. |  6. | 5.| 4.|  3. | 2.|  1.
  -----------+----+----+---+----+-----+-----+-----+---+---+-----+---+-----
       16    |33·3|45·4| 60|77·7|100  |128·5|166·6|220|300|433·3|700|1,500
       15    |25·0|36·4| 50|66·6| 87·5|114·3|150  |200|275|400  |650|1,400
       14    |16·6|27·3| 40|55·5| 75  |100  |133·3|180|250|366·6|600|1,300
       13    | 8·3|18·2| 30|44·4| 62·5| 85·7|116·6|160|225|333·3|550|1,200
       12    |    | 9·1| 20|33·3| 50  | 71·4|100  |140|200|300  |500|1,100
       11    |    |    | 10|22·2| 37·5| 57·1| 83·3|120|175|266·6|450|1,000
       10    |    |    |   |11·1| 25  | 42·8| 66·6|100|150|233·3|400|  900
        9    |    |    |   |    | 12·5| 28·5| 50  | 80|125|200  |350|  800
        8    |    |    |   |    |     | 14·2| 33·3| 60|100|166·6|300|  700
        7    |    |    |   |    |     |     | 16·6| 40| 75|133·3|250|  600
        6    |    |    |   |    |     |     |     | 20| 50|100  |200|  500
        5    |    |    |   |    |     |     |     |   | 25| 66·6|150|  400
        4    |    |    |   |    |     |     |     |   |   | 33·3|100|  300
  -----------+----+----+---+----+-----+-----+-----+---+---+-----+---+-----

_Antichlors._--The residues of chlorine which may be left in pulp after
bleaching are frequently neutralised by the use of substances termed
antichlors, which react with the calcium hypochlorite, converting it
into chlorides.

The sodium hyposulphite is the most frequently used antichlor, the
reaction between this and hypochlorite resulting in the formation of
calcium sulphate and sodium chloride; 100 lbs. of commercial bleaching
powder will require 30 lbs. of crystallised sodium hyposulphite.

The sulphites of soda and lime also act as antichlors, reducing the
hypochlorite of calcium into sulphate of lime or soda. The chief
advantage of the use of sulphites is to be found in the fact that the
substances obtained by the reaction are neutral.

The best practice in bleaching is to avoid the necessity for using any
forms of antichlors by careful regulation of the bleaching process. It
has already been suggested in previous references to bleaching that
the desired results are obtained when the pulp and bleach are left
in contact with one another in tanks or drainers until the bleach is
completely exhausted, the residual salts in solution being removed by
thorough washing.

_Gelatine._--For animal-sized or tub-sized papers gelatine is used. It
can be prepared by the paper-maker from hide clippings, sheep skins,
bone, etc., or can be purchased ready made.

Beadle gives the following interesting details as to the amount of
gelatine which can be obtained from wet hide pieces:--

WEIGHT OF WET HIDE PIECES, 2,128 LBS.

        -------------+--------+-----------+----------
                     |        | Per cent. |Weight of
        Draught.     |Gallons.|Gelatine in|Gelatine.
                     |        | Solution. |   Lbs.
        -------------+--------+-----------+----------
              1      | 126·48 |   6·775   |  85·64
              2      | 128·96 |   6·052   |  78·04
        3 and 4 mixed| 135·20 |   9·446   | 127·63
                     +--------+           +----------
              Total  | 390·64 |           | 291·31
        -------------+--------+-----------+----------

Percentage of gelatine on weight of wet skins = 13·69.

A similar trial on the same class of wet hide pieces gave a yield of
13·23 per cent.

Two trials, of a somewhat different class of wet hide pieces, gave
respectively 13·11 and 12·8 per cent.

The temperature of the draught water should be approximately as
follows:--

          --------+-------------+----------
          Draught.|At Beginning.|  At End.
          --------+-------------+----------
             1    |   120° F.   |   150° F.
             2    |   130° F.   |   160° F.
          3 and 4 |   140° F.   |   180° F.
          --------+-------------+----------

In the final draught it is often necessary to use live steam at the
finish, but this should be avoided if possible.

The water contained in wet hide pieces varies from 77 to 90 per cent.
in the different pieces, but in the bulk the average may be taken at 85
per cent.

_Casein._--Casein is the nitrogenous principle of milk, and belongs
to the class of proteids which are definite compounds of oxygen,
hydrogen, carbon, and nitrogen, forming the basis of the most important
constituents of all animal fibres, albumen, casein, and gluten. A very
pure form of casein is cheese made from skimmed milk. Casein belongs to
that class of albumens which are soluble in water, _e.g._, egg albumen,
blood albumen or serum, and lactalbumen, or milk albumen; these are
mostly precipitated from solution by saturation with sodium chloride
(common salt) or magnesium sulphate; but they are all coagulated by
heat.

By the action of rennet on milk the proteid or albumen principle is
converted into a curd (casein). This curd, when freed from fats, is
insoluble in water, but is soluble in dilute acids, or alkalies,
or alkaline carbonates, from which substances, however, it is
reprecipitated by acidulation. Instead of the above method, casein may
be precipitated from milk by saturation with sulphate of magnesia, and
washing the precipitate with a solution of that salt until the washings
contain no albumen, and then redissolving the prepared casein by
adding water. The salt still adhering to the precipitate enables it to
dissolve. On a large scale the casein is usually prepared by treating
the milk with acid.

Casein is readily dissolved by alkalies and alkaline carbonates, borax,
boracic acid solution, caustic soda, and bicarbonate of soda.

_Starch._--This substance is used in many classes of paper for
improving the surface and finish. It is added to the pulp in the
beating engine in the dry form as powder, or in the form of starch
paste, produced by boiling the starch in water.

The viscosity of the starch paste is somewhat increased by the addition
of a small quantity of alkali, but due care must be exercised in
boiling, which should only be carried out sufficiently to cause the
starch granules to burst, as any excessive boiling causes the starch
paste to lose some of its viscosity.

The presence of starch in paper is detected by the blue coloration
produced when the paper is dipped into a weak solution of iodine. The
determination of the exact percentage of starch in a paper is a matter
of some difficulty.

_Silicate of Soda._--The precipitation of gelatinous silica upon the
pulp in the beating engine is generally regarded as favourable to the
production of a sheet of paper having what is known as a harder finish.
The precipitation is effected by adding a solution of silicate of soda
to the beating engine, with the subsequent addition of sufficient
sulphate of alumina to react with the silicate of soda.


ANALYSIS OF COMMERCIAL ALUMS.

(Griffin and Little.)

  ---------------------------------+------+------+------+------
                                   | (1)  | (2)  | (3)  | (4)
  ---------------------------------+------+------+------+------
  Insoluble in water               |  0·05| 10·61|  0·11|  0·56
  Alumina (Al_{2}O_{3})            | 15·47| 14·96| 11·64| 16·58
  Iron protoxide (FeO)             |  0·02|  0·13|  0·06|   --
  Iron sesquioxide (Fe_{2}O_{3})   |  0·00|  1·08|  1·17|  0·04
  Zinc oxide (ZnO)                 |   -- |   -- |   -- |   --
  Soda (Na_{2}O)                   |  1·72|  0·57|  4·75|  0·56
  Magnesia (MgO)                   |   -- |   -- |  0·45|   --
  Sulphuric acid (SO_{3}) combined | 37·26| 37·36| 35·98| 39·17
  Sulphuric acid (SO_{3}) free     |   -- |  1·08|  5·13|   --
  Water by difference              | 45·48| 34·21| 40·71| 43·09
  ---------------------------------+------+------+------+------
                                   |100·00|100·00|100·00|100·00
  ------------------------------- -+------+------+------+------
  Sizing test (parts of dry neutral|      |      |      |
    rosin size precipitated by one |      |      |      |
    part of the alum)              |  3·32|  3·47|  3·19|  3·71
  ------------------------------- -+------+------+------+------


TABLE SHOWING VALUE OF SOLUTIONS OF ALUMINIUM SULPHATE.

  ---------+------------------------------------------
           |        Pounds per 100 gallons.
           +------------------------------------------
  Twaddell.|Al_{2}O_{3}. | SO_{3}. |Sulphate of
           |                       |Alumina
           |                       |containing 15 per
           |                       |cent. Al_{2}O_{3}.
  ---------+-------------+---------+------------------
       1   |      1·4    |    3·3  |        9·0
       2   |      2·8    |    6·5  |       19·0
       3   |      4·2    |    9·8  |       28·0
       4   |      5·6    |   13·0  |       37·0
       5   |      7·0    |   16·3  |       47·0
       6   |      8·4    |   19·6  |       56·0
       7   |      9·8    |   22·8  |       65·0
       8   |     11·2    |   26·1  |       75·0
       9   |     12·6    |   29·4  |       84·0
      10   |     14·0    |   32·6  |       93·0
      11   |     15·4    |   35·9  |      103·0
      12   |     16·8    |   39·1  |      112·0
      14   |     20·3    |   47·3  |      135·0
      16   |     23·1    |   53·8  |      155·0
      18   |     26·2    |   60·3  |      172·0
      20   |     29·4    |   68·5  |      196·0
      25   |     37·1    |   86·5  |      247·0
      30   |     44·8    |  104·4  |      299·0
      35   |     53·2    |  124·0  |      355·0
      40   |     60·9    |  142·0  |      405·0
      45   |     68·6    |  159·9  |      456·0
      50   |     77·7    |  181·0  |      578·0
      55   |     86·1    |  200·6  |      575·0
      60   |     95·2    |  221·8  |      635·0
  ---------+-------------+---------+------------------

_Alum._--Alum is one of the most important substances required in the
manufacture of paper, its chief function relating to the sizing of
paper. Various forms are utilised for this purpose, the purest being
sulphate of alumina, required for high grade papers, and the cheaper
form known as alum cake, for news and common printing.

The alum is manufactured on a large scale by heating china clay or
bauxite with sulphuric acid. This reaction gives sulphate of alumina
together with silica. If the mass is heated to dryness, it is sold
under the name of _alum cake_. If the mass is extracted with hot water
and the insoluble silica filtered off, the solution can be evaporated
down for the production of _sulphate of alumina_, which is sold in the
form of large cakes or in the form of crystals.

By careful selection of raw material a sulphate of alumina can be
prepared almost entirely free from iron. The presence of the latter is
undesirable, since on exposure to air the sulphate of iron produced
during the manufacture of the alum is slowly oxidised and turns brown.
Ultimately this affects the colour of the finished paper.

Alum is added to solutions of animal size or gelatine in order to
thicken the solution and render it more viscous. It also acts as a
preservative, and is used for regulating the absorption of the gelatine
by the paper, the penetration effects being materially varied by the
extent to which the alum is utilised.

In the process of engine sizing, a term applied to the application of
rosin size on account of the fact that the process is completed in
the beating engine, alum plays an important part. The mere addition
of the prepared rosin soap to the mixture of pulp and water in the
beating engine does not size the paper, but the alum precipitates the
rosin from its solution, producing a complex mixture said to consist
of resinate of alumina and free rosin particles, and subsequently the
heat of the paper machine drying cylinders renders the paper more or
less impermeable to moisture.

The appearance and tone of paper, more particularly of coloured papers,
are brightened by the use of an excess of alum over and above that
necessary to precipitate the rosin soap.

_Rosin Size._--This substance is used chiefly for the sizing of news
and cheap printing papers, and is also employed together with gelatine
for the commoner writing papers. It is prepared by boiling rosin with
carbonate of soda under various conditions.

Rosin, sometimes called colophony, is obtained from the sap of certain
firs and pine trees. This on distillation yields spirits of turpentine,
leaving behind as a residue the mixture of substances to which is given
the name rosin. It behaves as an acid, and therefore will combine with
certain alkaline oxides, producing soluble resinates.

The nature of the rosin soap used in the paper mill varies according to
the conditions under which the size is prepared. If a large proportion
of rosin is used, then the size obtained consists of a mixture of
resinate of soda together with free rosin dissolved in the solution. If
the proportion of rosin is small compared with the amount of carbonate
of soda, the composition of the final mixture is quite different. The
difference in treatment results in the formation of--

(_A_) _Neutral Size_, prepared by boiling a known weight of rosin with
sufficient alkali to combine with it and form a neutral resinate of
soda. Theoretically this may be obtained by using 630 parts of rosin to
100 parts of soda ash. It is doubtful how far the reaction is completed
so as to produce an exactly neutral solution containing only resinate
of soda.

(_B_) _Acid Size._--When the proportion of rosin is largely increased
the soda becomes converted into the alkaline resinate, and the excess
of rosin is gradually dissolved in the resinate formed.

The practical operations necessary for the preparation of the size are
comparatively simple. In the case of size containing relatively small
percentages of free rosin, the boiling is conducted in open vessels,
but for the manufacture of rosin size containing large proportions of
free rosin boiling under pressure in closed vessels must be resorted to.

With the open pan process a steam jacketed pan is used, and the
required quantity of alkali, dissolved in water, is placed therein and
heated to boiling point. The rosin well powdered is added in small
quantities from time to time, this being effected cautiously in order
that the carbonic acid gas set free during the process may readily
escape. The rosin is generally completely saponified after four or five
hours' boiling. It is then passed through strainers into store tanks,
from which it is drawn into the beating engines as required.

In the case of rosin boiled under pressure a cylindrical vessel
provided with a manhole at the top is used. The correct amounts of
alkali and water are put into the digester, and also the rosin in a
powdered form, the digester being fitted with a perforated plate placed
about two feet above the bottom of the vessel in order to prevent the
rosin forming into a hard mass at the bottom of the digester.

It is possible in this way to manufacture a thick size containing 30
or 40 per cent. of free rosin and a comparatively small proportion of
water. Many paper mill firms prefer to purchase such size ready made.

The most recent modification of the ordinary rosin size is a compound
prepared by treating rosin with silicate of soda. This alkali dissolves
rosin readily, and the soap obtained when suitably diluted with
water decomposes in the beating engine on the addition of aluminium
sulphate, with the precipitation of a gelatinous silica which assists
in hardening the paper.

Bacon has patented a process in which powdered rosin is melted down
with dry crystalline silicate of soda. The resultant product is ground
to a fine powder, which is then ready for use. It dissolves easily in
water, and when decomposed with the proper proportion of alum gives a
gelatinous viscous mass said to have excellent sizing properties.

The advantages of a dry powdered rosin size readily soluble in water
are obvious.

_Loading._--The term "loading" is applied to the various substances
which are employed for the purpose, as it is commonly supposed, of
making paper heavy. But china clay and similar materials are not added
simply in order to give weight to the paper, since they serve to
produce opacity and to improve the surface of papers which could not be
satisfactorily made unless such materials were used.

_Examination of Paper for Loading._--If a piece of paper is crumpled
up, placed in a small crucible, and then ignited until all the
carbonaceous matter has been burnt off, a residue is left in the
crucible which may be white or coloured. This is usually termed the
_ash_ of the paper. The amount of ash present is determined by taking
a weighed quantity of paper and weighing the residue obtained. Special
appliances can be obtained for making rapid determinations of the ash
in paper, but for occasional analyses they are not required.

_China Clay._--This is the best known and most commonly used loading.
The purest form of this material is kaolin, a natural substance formed
by the gradual decomposition of felspathic rocks arising from exposure
to the long-continued action of air and water. The clay occurs in great
abundance in Dorset, Cornwall, and Devon, the southern counties in
England, where the most famous deposits are found.

The natural mineral is levigated with water, and the mixture allowed
to flow through a series of settling ponds, so that the clay gradually
settles in the form of a fine deposit. The clay is dried and packed
in bags. Its value is controlled largely by the purity of its colour
and its freedom from grit and sand. It is essentially a silicate of
alumina, having the approximate composition--

        Silica (SiO_{2})          43·00
        Alumina (Al_{2}O_{3})     35·00
        Combined water            10·00
        Moisture and impurities   12·00
                                 ------
                                 100·00

The specific gravity of the dry substance is 2·50.

It is utilised as a loading in all kinds of paper, and forms also the
main ingredient in the coating found on ordinary art and chromo papers.

_Ash containing China Clay._--In news, cheap printings, and common art
papers the ash almost invariably contains china clay. This substance is
insoluble in dilute acids, but is acted upon by concentrated sulphuric
acid when digested for some time. A simple test for the presence of
china clay in ash is the blue coloration which is obtained when the ash
after being ignited is gradually heated with a few drops of solution of
cobalt nitrate. China clay can be decomposed by fusion with carbonate
of soda in a crucible. By this means silicate of alumina is decomposed,
and the alumina goes into solution, the silica remaining as an
insoluble residue. The filtered solution is boiled with an excess of
ammonia which gives a gelatinous precipitate of aluminium hydrate.

_Sulphate of Lime._--This compound is valued chiefly for its brilliancy
of colour, being used in high-class papers. It is slightly soluble in
water, to the extent of about 23 lbs. in 1,000 gallons, and this fact
must be taken into account when the material is added to the pulp in
the beating engine.

It occurs naturally in a variety of forms, such as gypsum, alabaster,
selenite, the first of which when finely powdered is sold to the
paper-maker as gypsum, powdered plaster, and under other fancy names.

It can be prepared artificially by adding sulphuric acid to solutions
of calcium salts; and the precipitated product so obtained is sold as
terra alba, pearl hardening, satinite, mineral white, etc.

The tests for sulphate of lime in paper ash are based upon the
following reactions:--

Calcium sulphate is soluble in dilute hydrochloric acid. The addition
of a few drops of barium chloride to the solution produces a dense
heavy precipitate, indicating the sulphate. A small quantity of
ammonium oxalate solution added to another portion of the dissolved
calcium salt previously neutralised with ammonia produces a precipitate
and indicates calcium.

A microscopic test of paper for the presence of sulphate of lime is
based upon the slight solubility of the salt in water. The paper is
boiled with some distilled water. The water is evaporated to a small
bulk and transferred to a glass slip, and the gradual formation of
characteristic sulphate of lime crystals can be seen by means of the
microscope as the water cools down.

_French Chalk._--This material is prepared by grinding talc into a
fine powder, and possesses a good colour and a somewhat soapy feel. It
is a silicate of magnesia, having the approximate composition--

    Silica (SiO_{2})          62·00
    Magnesia (MgO)            33·00
    Water                      4·30
    Traces of oxides, etc.     0·70
                             ------
                             100·00

Other silicates of magnesia used for paper-making are agalite and
asbestine, the latter being a finely ground asbestos.

The composition of asbestos is approximately--

    ---------------------------+----------+-----------
             --                | Italian. | Canadian.
    ---------------------------+----------+-----------
    Lime and magnesia          |   38·0   |   33·0
    Silica                     |   42·0   |   41·0
    Oxides of iron and alumina |    5·0   |   12·0
    Total water                |   13·0   |   12·0
    Traces of soda, etc        |    2·0   |    3·0
                               +----------+-----------
                               |  100·00  |  100·00
    ---------------------------+----------+-----------




CHAPTER IX

THE PROCESS OF BEATING


_Introduction._--The process of beating has for its object the complete
breaking down of the bleached pulp to the condition of single fibres,
and the further reduction of the fibres, when necessary, into smaller
pieces. The disintegration of the material is essential for the
production of a close even sheet of paper, and the amount of beating
required varies greatly according to the nature of the raw material,
and the class of paper to be produced.

The textile trade, on the other hand, depends on a raw material
composed of strong fibres, or of filaments characterised by great
length, and any processes of treatment which tend to reduce the length
of such fibres are carefully avoided, and it is therefore obvious that
fibres which are of no value for textile purposes can be appropriated
for paper-making.

_Condition of Fibres._--The great differences in the physical
characteristics and structure of the fibres employed for paper-making
suggest that the possible variations in the final product obtained by
beating are very numerous. This is a well-known fact, and it is further
to be noted that this mechanical operation brings about not merely
alterations of a physical order, but introduces some interesting and
important chemical changes.

Of the better-known materials linen, with an average fibre length of 28
mm., the structure of which lends itself to considerable alteration by
beating, is in marked contrast to esparto, the fibre length of which
is only 1·5 mm. If the process of beating a linen rag merely resulted
in the cutting of all the fibres of 28 mm. long into short fragments of
1·5 mm., there would be nothing remarkable in it, but the changes which
occur in reducing the long linen fibre to 1·5 or 2·0 mm. are of a far
more important character than this.

_Early Methods._--In the early days of paper-making the disintegration
of the half-stuff was effected by a true "beating" process, the rags
being subjected to the action of heavy stampers, which broke up the
mass of tangled fibre into a uniform pulp. The fibres for the most part
retained their maximum length in this operation, which was exceedingly
slow and tedious, though at the same time giving a sheet of paper of
remarkable strength.

The nearest imitation of these old-time rag papers is to be seen in
the well-known Japanese papers, which are extraordinarily strong. Some
of these the writer has examined in order to determine the length of
the fibre. The sheets when held up to the light appear "cloudy" and
"wild" owing to the presence of the long fibres, which have only been
separated or teased out by the primitive methods of beating used, and
not completely disintegrated.

_Conditions of Beating._--About A.D. 1700 there began a great epoch
in the history of paper-making. With the invention of the Hollander
engine about A.D. 1670, the process of disintegration was greatly
hastened, because it was possible to reduce the half-stuff much more
readily. The substitution of the idea of plain "beating" by a principle
which combined the gradual isolation of the individual fibres with a
splitting up of those fibres lengthwise and crosswise was not only an
advantage in point of economy of time and cost, but also a material
advance in the possibilities of greater variations in the finished
paper.

The conditions of the process of beating carried out with a Hollander
permit of considerable alteration, so that these changes in the fibre
are not surprising when properly understood. In fact, it is now
conceded that a close study of the theory and practice of beating
is likely to bring about still more remarkable improvements in this
important department of the paper-maker's work. The quality and
character of the paper made may be varied with--

(1) The origin of the raw material, _e.g._, rags, esparto, or wood;

(2) The condition of the material, _e.g._, old or new rags, green or
mature esparto, mechanical or chemical wood pulp;

(3) The time occupied in beating, _e.g._, four hours for an ordinary
rag printing and twelve hours for a rag parchment;

(4) The state of the beater knives, _e.g._, sharp tackle for blottings
and dull tackle for cartridge papers;

(5) The speed of the beater roll, also its weight;

(6) The rate at which the beater roll is lowered on to the bedplate;

(7) The temperature of the contents of the engine.

_The Beater Roll._--If the beater roll is fitted with sharp knives, and
this is put down close to the bedplate quickly, the fibres are cut up
short, and they do not assimilate the water. If the roll is fitted with
dull knives, or "tackle," as it is sometimes called, and it is lowered
gradually, the fibres are drawn and bruised out without being greatly
shortened. In this condition the stuff becomes very "wet," or "greasy,"
as it is termed. The cellulose enters into association with water when
beaten for many hours, and the pulp in the beating engine changes into
a curious greasy-like mass of a semi-transparent character. Rag pulp
beaten for a long time produces a hard, translucent, dense sheet of
paper. Flax thread beaten 48 to 60 hours is used in practice for the
manufacture of gramophone horns and similar purposes.

Soft porous papers like blottings, filtering papers, heavy chromos,
litho papers, antiques, light printings, are made from pulps which are
beaten quickly with the roll put down close to the bedplate soon after
the stuff has been filled in.

With strong, dense, hard papers, such as parchments, banks,
greaseproofs and the like, the pulp is beaten slowly and the roll
lowered gradually.

The nature of the pulp and the time occupied in beating are also
important factors in producing these different papers, three to four
hours being ample for an ordinary wood pulp printing, whereas a wood
pulp parchment requires seven to eight hours.

_Beating Pulps Separately._--The use of esparto and wood pulp in
conjunction with one another, or blended with rag, has introduced new
problems into the question of beating. Perhaps the most important
of these is the advisability of beating the pulps separately and
eventually passing them through a mixer of some kind before discharging
into a stuff chest. The necessity for differentiating the amount of
beating is already partly recognised when very dissimilar pulps, such
as strong rag and esparto, are blended, but the whole subject ought to
be carefully studied by the paper-maker and investigated on its merits
from the standpoint of "beating effects," apart from questions of cost
and expediency. The former fully understood and exhaustively examined
by practical tests would of course only be developed if proved to be
advantageous.

The field of research in this direction has not yet been seriously
explored. With the enormous consumption of wood pulps of varying
quality made from many different species of wood by several processes,
there is ample room for interesting and profitable enquiry,
particularly as the types of beating engine are so numerous. The
effects produced by the Hollander, the refiner, the edge runner, the
stone beater roll, and other mechanisms, are all of varying kinds.


EFFECT OF PROLONGED BEATING.

The importance of a knowledge of the precise effects produced by the
beating of pulp cannot be emphasised too much, and any contributions to
the subject along the lines of special research will be welcomed by all
students of cellulose.

[Illustration: FIG. 46.--Cotton Pulp beaten 8 hours.]

Some experiments were conducted by the writer in 1906 with cotton rags,
in order to determine the results obtained by beating the pulp for a
prolonged period under exact and specific conditions.

[Illustration: FIG. 47.--Cotton Pulp beaten 37 hours.]

The cotton rags, of good quality, were boiled with caustic soda in
the usual way for six or seven hours, at a pressure of 15 to 20 lbs.,
washed and partially broken down in the rag breaker, and finally
bleached, made into half-stuff, and then transferred to a Hollander
beating engine.

The particular conditions specified for the beating operation were that
the beaterman should manipulate the pulp according to his usual routine
for the manufacture of the paper which he was accustomed to make from
these rags. In this case the routine process meant beating for eight
hours, by which time the pulp was ready for the paper machine. In the
ordinary course the pulp would be discharged into the stuff chest, and
converted into a strong, thin, bank paper.

During the prolonged beating the pulp became very soft and "greasy,"
and when made up into sheets the paper as it dried exhibited remarkable
differences in shrinkage, the dry sheets obtained from pulp beaten
thirty-seven hours being much smaller than those obtained from pulp
beaten only four or six hours. The actual shrinkage is shown in the
following table:--

    ------+---------------+----------------+--------------+----------
          |               |                |   Relative   |
    Hours.| Area of Sheet.|  Loss of Area. |    Areas.    |Shrinkage
          |    Sq. mm.    |    Sq. mm.     |  Deckle 100  |per cent.
    ------+---------------+----------------+--------------+----------
      0   |   26,384·0    |         --     |    100·0     |   --
      4   |   26,076·0    |       308·0    |     98·9     |   1·1
      6   |   25,520·1    |       863·9    |     96·7     |   3·3
      8   |   25,160·0    |     1,224·0    |     95·4     |   4·6
     10   |   24,794·8    |     1,589·2    |     93·9     |   6·1
     13   |   24,467·4    |     1,916·6    |     92·8     |   7·2
     15   |   24,215·2    |     2,168·8    |     91·8     |   8·2
     17   |   24,024·0    |     2,360·0    |     90·9     |   9·1
     19   |   23,616·2    |     2,767·8    |     89·6     |  10·4
     21   |   23,616·0    |     2,768·0    |     89·6     |  10·4
     23   |   23,535·7    |     2,848·3    |     89·3     |  10·7
     25   |   23,329·9    |     3,054·1    |     88·5     |  11·5
     27   |   22,920·5    |     3,463·5    |     86·9     |  13·1
     29   |   22,831·2    |     3,552·8    |     86·5     |  13·5
     31   |   22,492·9    |     3,891·1    |     85·3     |  14·7
     33   |   21,917·2    |     4,466·8    |     83·1     |  16·9
     35   |   21,226·1    |     5,157·9    |     80·5     |  19·5
     37   |   20,778·8    |     5,605·2    |     78·8     |  21·2
    ------+---------------+----------------+--------------+----------

If these results are plotted in the form of a curve the relation
between the period of beating and the shrinkage in area is clearly
shown. For the first twenty hours the shrinkage is proportional to the
period of beating, after which the curve assumes an irregular shape,
showing a tendency for shrinkage to proceed at a faster rate.

_Weight and Substance of the Paper._--The shrinkage of the paper after
prolonged beating indicates a closer and denser sheet, so that for
papers of equal thickness the weight per unit area was much greater in
the case of the pulp beaten for the full period. The results obtained
are very interesting, and the following summary for a few of the
readings obtained will serve to show the alteration effected.

  ----------+--------------+--------------+------------+---------------
            |  Weight of   | Thickness of | Grams per  | Lbs. per ream
  Hours.    |20,000 sq. mm.|    Sheet.    | sq. metre. | 480 sheets,
            |  Grams.      |     mm.      |            |   20" × 30".
  ----------+--------------+--------------+------------+---------------
   Class A  |              |              |            |
  8-10 hrs. |    1·875     |     ·183     |    93·75   |   38·23
            |              |              |            |
   Class B  |              |              |            |
  19-21 hrs.|    2·043     |     ·189     |   102·15   |   41·65
            |              |              |            |
   Class C  |              |              |            |
  33-35 hrs.|    2·203     |     ·189     |   110·15   |   44·93
  ----------+--------------+--------------+------------+--------------

_Sizing and Glazing Effects._--The behaviour of the waterleaf paper
after sizing and glazing gave some interesting results. In the first
place, the effect of the altered density of the paper is strikingly
shown by the amount of the size absorbed. Certain selected sheets
were passed through a solution of ordinary gelatine in the usual way,
and subsequently dried. The amount of gelatine absorbed differs in a
remarkable degree, as shown in table.

_Tensile Strength of the Paper._--It is interesting to note that the
tensile strength of the waterleaf papers appears to remain fairly
constant throughout the whole period of beating. But this uniformity is
greatly altered by the operations of sizing and glazing.


PERCENTAGE OF AIR-DRY GELATINE ABSORBED BY THE WATERLEAF SHEETS.

    ----------+-----------------------------------+---------
              |   Percentage of Size absorbed.    |
      Hours.  +-----------+-----------+-----------+  Mean.
              | 1st Trial.| 2nd Trial.| 3rd Trial.|
    ----------+-----------+-----------+-----------+---------
        8     |    5·5    |    6·0    |    6·2    |   5·9
       10     |    5·4    |    6·8    |    6·5    |   6·2
       19     |    3·8    |    5·0    |    4·5    |   4·4
       21     |    4·8    |    3·9    |    4·6    |   4·4
       33     |    2·7    |    1·7    |    2·4    |   2·3
       35     |    2·4    |    1·9    |    1·7    |   2·0
    ----------+-----------+-----------+-----------+---------

These results are rather remarkable. The prolonged beating does not
seem to have affected the tensile strength of the waterleaf, and the
practical loss of strength which actually occurs in the more completely
finished paper does not manifest itself until after the sizing process.
The importance of the gelatine as a factor in the ultimate strength is
thus clearly and strikingly demonstrated.


TESTS FOR STRENGTH ON ORIGINAL WATERLEAF PAPER.

        --------------+--------------+--------------
                      |Mean result of|Mean Strength
           Hours.     |  Readings.   |of the Paper.
                      |    Lbs.      |   Lbs.
        --------------+--------------+--------------
             8        |   a  14·1    |    12·1
                      |   b  10·1    |
            10        |   a  15·4    |    13·2
                      |   b  10·9    |
            19        |   a  16·5    |    14·0
                      |   b  11·4    |
            21        |   a  15·2    |    14·0
                      |   b  12·8    |
            33        |   a  13·4    |    12·4
                      |   b  11·4    |
            35        |   a  14·5    |    13·6
                      |   b  12·7    |
        --------------+--------------+--------------


TESTS FOR STRENGTH ON PAPERS, SIZED ONLY.

        --------------+--------------+--------------
                      |Mean result of|Mean Strength
           Hours.     |  Readings.   |of the Paper.
                      |    Lbs.      |   Lbs.
        --------------+--------------+--------------
             8        |   a  22·7    |    20·0
                      |   b  17·3    |
            10        |   a  28·5    |    23·2
                      |   b  18·0    |
            19        |   a  22·5    |    21·0
                      |   b  19·5    |
            21        |   a  26·0    |    21·7
                      |   b  17·5    |
            33        |   a  15·0    |    15·0
                      |   b  15·0    |
            35        |   a  14·2    |    15·3
                      |   b  16·5    |
        --------------+--------------+--------------


TESTS FOR STRENGTH ON PAPER SIZED AND GLAZED.

        --------------+--------------+--------------
                      |Mean result of|Mean Strength
           Hours.     |  Readings.   |of the Paper.
                      |    Lbs.      |   Lbs.
        --------------+--------------+--------------
             8        |  a  25·8     |    23·6
                      |  b  21·4     |
            10        |  a  28·4     |    23·6
                      |  b  18·9     |
            19        |  a  27·0     |    22·9
                      |  b  18·9     |
            21        |  a  24·9     |    22·7
                      |  b  20·6     |
            33        |  a  16·1     |    15·2
                      |  b  14·4     |
            35        |  a  17·5     |    16·2
                      |  b  15·0     |
        --------------+--------------+--------------

It may also be noticed that the strength of the finished paper after
twenty hours' beating, as in class B, is equal to that of the paper
after nine hours' beating, as in class A. This is curious, especially
in view of the fact that the percentage of gelatine in the papers of
class B. is only 4·4 per cent. as against 6·0 per cent. in class A.

The relation of the percentage of gelatine to the period of beating
thus becomes a matter of interest, and well worth investigation. The
figures are suggestive of further experimental research along definite
lines.

[Illustration: FIG. 48.--Plan and Sectional Elevation of a "Hollander."]

_Developments in Beating Engines._--Since the introduction of the
Hollander beating engine, about A.D. 1670, other types of beater almost
too numerous to mention have been devised to supersede it, but the fact
remains that the principle of the original Hollander and its general
design are still adhered to in the engines used by paper-makers for
high-class work.

The alterations and improvements which have taken place during the
last fifty years relate chiefly to the modifications naturally arising
from the introduction of fibres not requiring such drastic treatment as
rags.

The machines now in use for reducing half-stuff to beaten pulp ready
for the paper machine may be classified as follows:--

(1) Beaters of the Hollander type, in which the circulation of the pulp
in the engine and the actual beating process are both effected by the
beater roll.

(2) Beaters of the circulator type, in which the movement of the pulp
is maintained by a special contrivance, and the beater roll used only
for beating.

(3) Beaters of the stone roll type in which the roll and bedplate are
either or both composed of stone, granite, or similar non-metallic
substance.

(4) Refiners, containing conical shaped beater rolls working in a
conical shell fitted with stationary knives.

[Illustration: FIG. 49.--Beating Engine with Four Beater Rolls.]

_The Hollander._--This beating engine in its simplest form consists of
an oval shaped trough, divided into two channels by a "midfeather,"
which does not, however, reach completely from one end to the other.

In one of the channels the bed of the trough slopes up slightly to the
place where the "bedplate" is fixed. The bedplate consists of a number
of stout metal bars or knives firmly fastened into an iron frame, which
lies across this channel. The beater roll, a heavy cast-iron roll
provided with projecting knives or blades arranged in clumps of three
around the circumference, and supported on bearings at each side of the
engine, revolves above the bedplate with the knives adjusted to any
required distance from it, the raising or lowering of the beater roll
for this purpose being effected by the use of adjustable bearings.

The bed of the trough behind the beater roll rises sharply up from the
bedplate and then falls away suddenly, as shown in the diagram, forming
the "backfall."

When the engine is in operation the mixture of water and pulp is drawn
between the knives and circulated round the trough. The material is
disintegrated into fibres of the required condition, discharged over
the backfall, and kept in a state of continual circulation, and the
beating maintained until the stuff has been sufficiently treated.

The dimensions of the engine vary according to the capacity, which is
usually expressed in terms of the amount of dry pulp the beater will
hold, and the following figures may be taken as giving the average
sizes:--

        -----------------+----------------+----------------
                --       | 2 cwt. Engine. | 5 cwt. Engine.
        -----------------+----------------|----------------
        Length           |  11 ft. 0 in.  |  16 ft. 0 in.
        Width            |   5 ft. 6 in.  |   8 ft. 0 in.
        Depth (average)  |   2 ft. 3 in.  |   2 ft. 9 in.
        Diameter of roll |   3 ft. 6 in.  |   3 ft. 6 in.
        -----------------+----------------+----------------

Sundry modifications in the form and arrangement of the beater
have been tried from time to time. In 1869 Granville patented the
substitution of a second beater roll in place of the stationary
bedplate for the purpose of hastening the operation. Repeated attempts
have been made to construct a beating engine with two or more rolls,
but it is evident that such a device could hardly succeed, since it
would be impossible to ensure proper adjustment of the rolls, and in
that case one roll might be doing all the work.

The first machine of this type was patented in 1872 by Salt. Similar
beaters were devised by Forbes in 1880, Macfarlane in 1886, Pickles in
1894, who proposed to use three rolls, and Partington in 1901. Hoffman
describes a beating engine which was working in America containing four
rolls, as shown in the diagram.

_The Umpherston._--A notable modification of the Hollander, having
an arrangement by which the two channels of the engines are placed
under one another, and one which is largely used for fibres, is the
Umpherston. Several engines differing in detail, but embodying the same
principle, have been built in imitation of this one.

[Illustration: FIG. 50.--Umpherston Beater.]

Bedplates of large working surface were first tried in England by Cooke
and Hibbert, in 1878, but in practice it has been found that no serious
deviations from the narrow type of plate are of much value. As a matter
of fact it is held by some paper-makers that one or two knives would
be sufficient if they could be relied on to keep true and in proper
adjustment.

_The Circulating Type of Beater._--The addition of some device for
keeping the pulp in circulation apart from the action of the roll
has received considerable attention. The early experiments in this
direction with the Hollander led ultimately to the construction of the
engine of the circulator type mentioned in class 2.

[Illustration: FIG. 51.--Section of Umpherston Beating Engine.]

Thus, in 1872, Nugent patented a special paddle to be used in the
Hollander, by which the pulp in the trough of the beater was impelled
towards the roll. Many other plans were tried for this purpose, and
details can be seen in the List of Patents (see page 192).

The introduction of the beaters with special means of circulating the
pulp was found to be of the greatest service in the treatment of stuff
like esparto and wood pulp, since these materials did not require the
drastic measures necessary with rag pulp. In 1890 several engines of
this class were being adopted, amongst which may be mentioned Hemmer's,
Reed's and Taylor's. The pulp discharged from the beater roll was drawn
through an independent pipe or channel by means of an Archimedean
screw, or a centrifugal pump.

_Stone Beater Rolls._--The substitution of stone for metal in the roll
and bedplate of the engine brings about some remarkable changes in the
nature of the beaten stuff. The fibre is submitted to the action of
rough surfaces rather than that due to the contact of sharp edges, with
the result that the disintegration is much more rapid, and produces
a "wet" working pulp suitable for imitation parchments and similar
papers. The latest materials used for this purpose are basalt lava
stone in Germany, and carborundum in America.

[Illustration: FIG. 52.--Nugent's Beating Engine with Paddles for
Circulating the Pulp.]

Care is necessary in the manipulation of these beaters to prevent
fracture of the stone parts. In the Wagg Jordan engine this danger is
materially reduced by the construction of the working parts.

_Refiners._--In these engines the beater roll is a conical shaped drum
carrying the knives, which revolve inside a conical shell completely
lined with fixed knives. The fibres are thus cut up to the desired
length, but before discharge from the engine they pass between two
circular discs, one stationary and the other revolving in a vertical
position. The effect of the discs is to tear or bruise the fibres
rather than to cut them.

The refiner is best employed to clear or brush out the mass of pulp
after a certain amount of preliminary treatment in the beater, as the
refiner cannot produce the effects obtained by actual beating as in the
Hollander.

[Illustration: FIG. 53.--A "Tower" Beating Engine with Centrifugal Pump
for Circulating Pulp.]

_Power Consumption._--The long treatment required to thoroughly pulp
a strong material demands a great amount of power. Engines differ
considerably in their power consumption, and comparisons are frequently
made in terms of the power required to beat a given weight of pulp.
But this is not always a true criterion of efficient work. Some types
of beater are suitable for producing certain results, and the mere
substitution of a beater consuming less power is worse than useless
unless it can be shown that the same effects are being obtained. The
efficiency of the Hollander for the beating of rag pulp, in spite of
the high power consumption, is a case in point.

[Illustration: FIG. 54.--Working Parts of a Modern Refining Engine.]

With this factor properly considered, the power required for beating
becomes an interesting study. Many detailed experiments have been
published from time to time, the most recent being those described by
Beadle.


PATENTS TAKEN OUT IN CONNECTION WITH BEATING ENGINES.

1855. PARK (1170).--A small steam engine was attached to the shaft of
the beater roll, so that it could be driven direct.

1856. KINGSLAND (2828).--A form of refiner in which the pulp was beaten
by a vertical disc rotating in an enclosed case.

1860. JORDAN (792).--A machine devised for mixing size with pulp, made
like a conical refining engine, the rubbing surface being provided with
teeth or cutters.

1860. JORDAN (2019).--An engine of the refiner type, constructed with a
conical drum rotating in a conical casing. The knives at the larger end
of the drum are placed closer together than those on the smaller end.

1863. PARK (1138).--Two beaters placed side by side are driven by one
steam engine placed between them, the operations being so timed that
one rag engine is used for breaking while the other is finishing.

1864. IBOTSON (2913).--The pulp is passed continuously from one engine
roll to another, or from one part of a beater roll to another part of
the same roll through slotted plates.

1866. ROECKNER (140).--A beating engine of the refiner type with
conical drum and casing.

1866. BERHAM (3299).--A beating engine of the conical type with the
beater roll rotating vertically instead of horizontally.

1867. CROMPTON (482).--Device for raising the bars in the beater roll
as the edge of the plate wears away.

1867. WOOD (914).--Modification in the form of the beater bars (of
little importance).

1867. EDGE (3673).--The knives of the beater roll distributed at equal
distances apart all round the roll, alternated with strips of wood.

1869. GRANVILLE (1041).--Substitution of a second beater roll for the
stationary bed-plate, the knives being set spirally round the roller.

1869. NEWELL (2905).--Weight of the beater roll counterpoised to allow
of the exact regulation of the pressure on the stuff in the beating
engine.

1870. ROSE (997).--An intercepting plate fixed to the cover of the
beating engine which causes that part of the stuff which was usually
carried right round by the roll to fall back behind the backfall.

1870. BENTLEY AND JACKSON (1633).--A beater roll having the same width
as the engine, and provided with a cover fitted with a pipe which
conducted the material back to the front of the roll.

1871. PATTON (1336).--Bottom of beating engine curved in order to
prevent the stuff settling or accumulating at any portion of the
machine.

1872. SALT (1901).--A beating engine of usual type, but having two
beater rolls and two drum washers, one pair in each of the two channels.

1873. GOULD (769).--A curious engine with horizontal shaft having
a circular disc at the lower end, fitted with knives on the
under-surface, which are in contact with fixed knives lying at the
bottom of the vessel. The circulation of the pulp is effected by the
centrifugal force generated.

1873. MARTIN (3751).--A beating engine with two rolls in the same
trough, the first roll working in conjunction with a smooth surfaced
beating roll, the other being in contact with a bedplate of the usual
type, the object of the first roll being to partially disintegrate the
material without danger of choking.

1874. JOHNSTONE (3708).--A pulping engine in which the rubbing action
of two grindstones one upon the other is utilised as a means of beating.

1876. GARDNER (307).--A beating engine in which the beater roll is
conical in shape, working vertically in contact with the bottom of the
beating engine, which is also conical in shape, the engine itself being
circular.

1878. COOKE AND HIBBERT (4068).--The bedplate constructed in the form
of a circular segment with a much larger face than usual, and capable
of adjustment, the beater roll itself being fixed in the bearings.

1880. FORBES (692).--A long oval shaped beating engine divided into
three channels instead of two. In the two outer channels are placed
beater rolls and drum washers. The stuff discharged over the backfalls
from the two beating engines flows down the central channel and is
circulated by a special paddle constructed in such a manner as to
deliver the pulp in two equal streams into the outer channels to each
of the beater rolls.

1880. UMPHERSTON (1150).--An engine constructed with a passage below
the backfall so that the stuff circulates in a trough underneath the
beater roll, the object being to ensure more effective treatment and to
save floor space.

1883. AITCHISON (5381).--A beating engine of usual form, but with
the beater roll made conical in shape with the larger circumference
outwards, and the bedplate placed on an incline parallel with the
knives on the beater roll.

1884. MAYFIELD (2028).--The backfall of the beating engine is of
entirely different construction to the ordinary machine, for the
purpose of improving the circulation.

1884. HOYT (11177).--An engine resembling the Umpherston, but with a
larger roll, the diameter of which is equal to the full depth of the
engine, the backfall being in a line with the axis of the beater roll.

1885. JORDAN (7156).--Additions to the Jordan engine for admitting
water and steam to the engine as required.

1885. KORSCHILGEN (9433).--The beater roll made of stone or of metal
with a stone casing furnished with ribs or knives placed close together.

1886. HIBBERT (4237).--A beating engine fitted with an ordinary beater
roll, and having in addition a heavy disc rotating vertically, the
disc being fitted with knives on one surface which rotate in contact
with knives fixed on a stationary disc.

1886. KRON (9885).--A device for securing better circulation of the
pulp, the stuff leaving the beater roll being divided into two streams
which are brought together again in front of the roll.

1886. HORNE (10237).--A long rectangular vessel with a large beater
roll at one end, contrived so as to force the pulp leaving the beater
roll to pass down a partition separating it from the pulp going towards
the beater roll.

1886. MACFARLANE (11084).--An engine fitted with two beater rolls which
rotate in opposite directions, the stuff being mixed between them.

1887. NACKE (746).--A centrifugal circulating wheel rotating
horizontally in the centre of the beating engine is used in combination
with a parallel cutting disc.

1887. MARSHALL (1808).--A conical refiner having in addition at its
large end a pair of grinding discs fitted with knives and rotating
vertically.

1887. VOITH (6174).--An alteration to the covers of the beater rolls
which prevent stuff from being carried round the cylinder, and cause it
to pass over the backfall freely.

1890. HEMMER (17483).--A beating engine provided with a separate
return channel for the pulp, the circulation through the channel being
effected by a small centrifugal pump.

1890. A. E. REED (19107).--A beating engine in which the pulp
discharged over the backfall is delivered to the front of the beater
roll by a screw propeller.

1891. KARGER (11564).--A beater similar to the Umpherston, but provided
with a circulating roll fitted with radial projections which delivers
the stuff to the front of the beater roll.

1892. TAYLOR (7397).--A beating engine in which the beater roll
operates in a closed chamber above the vat full of pulp, the stuff
being continually circulated by a centrifugal pump which draws the
stock from the bottom of the vat and delivers it to the beater roll.

1892. ANNANDALE (9173).--A conical-shaped beating engine with the
beater roll rotating in a vertical position; the larger end of the cone
being downwards.

1892. UMPHERSTON (15766).--An addition to the beating engine arranged
so that two fixed bedplates are used instead of one.

1892. MILLER (15947).--A machine in which two fixed bedplates are used,
one below the beater roll and one above, the engine being fitted with
suitable baffle plates to ensure proper circulation.

1893. PEARSON AND BERTRAM (11956).--A special form of refining engine
in which the pulp is subjected to the action of discs rotating
vertically, the knives being arranged radially on the disc.

1893. CALDWELL (15332).--A rotary beating engine in which the beating
surfaces admit of accurate adjustment.

1894. CORNETT (945).--An outlet is fixed to the beater roll casing
close to the discharge from the bedplate, so that the roll is not
impeded by the weight of the pulp, which is subsequently pumped to the
front of the beater roll.

1894. SHAND AND BERTRAM (4136).--A beating engine similar to the
Umpherston beater in which the beater roll is raised up out of the pulp
and the circulation effected by means of a worm which delivers the pulp
to the front of the beater roll.

1894. PICKLES (20255).--A beating engine somewhat similar to an
Umpherston, but fitted with three beater rolls and bedplates.

1894. HIBBERT (25040).--A beating engine in which the pulp is beaten
between two discs rotating vertically, the pulp being brought between
the discs through the hollow shaft of one of the discs.

1895. BROWN (1615).--An engine in which the beater roll and bedplate
both revolve, but in opposite directions, and at different speeds in
order to draw out the fibres.

1895. SCHMIDT (24730).--A device by means of which the pulp discharged
from the beater roll is diverted into supplementary channels on either
side which come together again in front of the beater roll.

1900. HADFIELD (2468).--An adjustable baffle board passing through the
cover of the beater roll which prevents the pulp being carried round by
the roll, more or less.

1900. MASSON AND SCOTT (5367).--An improved form of Taylor beating
engine in which the chest of the engine is vertical instead of
horizontal.

1901. PARTINGTON (24654).--A continuous elliptical trough provided with
two beater rolls.

1902. PICARD (19635).--Improvements in the form of the propellers used
for circulating the material.

1902. POPE AND MULLEN (22089).--Improvements in propellers for
circulating the pulp.

1903. ANNANDALE (26012).--A new form of beating engine somewhat on the
principle of a steam turbine.

1905. BERTRAM (1727).--A beater similar to Masson's tower beater, but
in which a pair of reciprocating wheels fitted with projecting knives
are used instead of a centrifugal pump.

1907. WAGG'S JORDAN ENGINE (6788).--A conical refiner fitted with
specially arranged metal or stone knives.




CHAPTER X

THE DYEING AND COLOURING OF PAPER PULP


Nearly all papers, even those commonly regarded as white, are dyed
with some proportion of colouring matter. With the ordinary writing
and printing papers the process is usually confined to the addition of
small quantities of pigments or soluble colours sufficient to _tone_
the pulp and correct the yellow tint which the raw material possesses
even after bleaching. In the case of cover papers, tissues, and similar
coloured papers, the process is one of dyeing as it is generally
understood.

The colouring matters which have been employed by the paper-maker are--


PIGMENTS.

(A) Added to the pulp in the form of mineral in a finely divided state.

  _Yellow._--This colour is obtained by the use of _ochres_, which are
    natural earth colours of varying shades, from bright yellow to
    brown.

  _Red._--Ordinary red lead.

    Various oxides of iron, such as Indian red, Venetian red, red
      ochre, rouge.

  _Blue._--_Smalts_--An expensive pigment prepared by grinding cobalt
    glass.

    _Ultramarine_--A substance of complex composition prepared by
      heating a mixture of china clay, carbonate of soda, sulphate
      of soda, sulphur, charcoal, and sometimes quartz, rosin and
      infusorial earth.

    _Prussian Blue_--A compound prepared by adding potassium
      ferrocyanide to a solution of ferrous sulphate.

  _Brown._--Natural earth colours, such as sienna, umber, Vandyke brown.

  _Black._--Lamp-black, bone-black, Frankfort black.

(B) Produced by the reaction of soluble salts upon one another when
added to the pulp in the beating engine.

  _Yellow._--_Chrome Yellow_--The paper pulp is first impregnated with
    acetate of lead, and potassium or sodium bichromate added. This
    precipitates the chromate of lead as a yellow pigment.

    _Chrome Orange_--The addition of caustic alkali to the bichromate
      solution converts the chrome yellow into an orange.

  _Blue.--Prussian Blue_--The paper pulp impregnated with iron salts
    is treated with potassium ferrocyanide. The blue colour is at once
    obtained.

  _Brown.--Iron Buff_--A light yellow-brown colour due to the
    precipitation of ferrous sulphate by means of an alkali.

  _Bronze._--Manganese chloride followed by caustic soda.


SOLUBLE COLOURS.

(A) Natural Dyes. These colouring matters are now seldom used.

  _Yellow and Brown._--The vegetable extracts, such as fustic,
    quercitron, cutch, turmeric, have practically all been replaced by
    aniline colours.

  _Red._--Madder (Turkey red), Brazilwood, cochineal (a dye obtained
    from dried cochineal insects). Safflower.

  _Black_.--Logwood, used in conjunction with an iron salt. Cutch, used
    with an iron salt.

(B) Coal Tar Dyes. The dyeing and colouring of paper pulp by means of
the artificial organic substances has become a matter of daily routine,
the expensive natural dyes and the ordinary pigments having been almost
completely superseded. The numerous colouring matters available may be
classified either by reference to their chemical constitution or simply
on general lines, having regard to certain broad distinctions.

If the latter classification is taken, then the dyes familiar to the
paper-maker may be divided into--

  (a) Acid dyes, so called because the full effect of the colouring
    matter is best obtained in a bath showing an acid reaction.

  (b) Basic dyes, so called because the colour is best developed in an
    alkaline solution, without any excess of mordant.

  (c) Substantive dyes, which do not require the use of a mordant, as
    the colour is fixed by the fibre without such reagents.

Some of the most frequently used colouring matters are shown in the
accompanying table on page 202.

The distinction between _acid_ and _basic_ dye-stuffs is largely due
to certain characteristics possessed by many of them. Thus magenta,
which is the salt of the base known as Rosaniline, belonging to the
basic colouring matters, a group of dyes which do not possess the
fastness of colour peculiar to acid dyes, has a limited application.
But by treatment with sulphuric acid magenta is converted into an
acid magenta, and this dye has wider application than the basic salt.
Similarly the basic dye called aniline blue is insoluble in water,
and therefore has only a limited use, but by treatment with sulphuric
acid it is converted into alkali blue, soluble blue and so on, which
dissolve readily in water and are good fast colours. The acid dyes
generally have a weaker colouring power than the basic dyes, but they
produce very even shades.

  -------+-------------------+-----------------+-----------------
  Colour.|      Acid.        |     Basic.      |  Substantive.
  -------+-------------------+-----------------+-----------------
  Yellow | Metanil yellow.   | Auramine.       | Cotton yellow.
  and    | Paper yellow.     | Chrysoidine.    | Chrysophenine.
  Orange.| Orange II.        |                 |
         | Naphthol yellow S.|                 |
         | Quinoline yellow. |                 |
         |                   |                 |
  Red.   | Fast red A.       | Rhodamine.      | Congo red.
         | Cotton scarlet.   | Paper scarlet.  | Benzopurpurin.
         | Erythrine.        | Safranine.      | Oxamine red.
         | Ponceau.          | Magenta.        |
         |                   |                 |
  Blue   | Water blue 1 N.   | Methylene blue. | Azo blue.
  and    | Fast blue.        | Victoria blue.  |
  Violet.| Acid violet.      | New blue.       |
         |                   | Indoine blue.   |
         |                   | Methyl violet.  |
         |                   | Crystal violet. |
         |                   |                 |
  Brown  | Naphthylamine     | Bismarck brown. |
         |   brown.          | Vesuvine.       |
         |                   |                 |
  Black  | Nigrosine.        | Coal Black B.   |
         | Brilliant black B.|                 |
         |                   |                 |
  Green  |                   | Diamond green.  |
         |                   | Malachite green.|
  -------+-------------------+-----------------+-----------------

The difference in the composition of the basic and acid dyes is
taken advantage of in the dyeing of paper pulp to secure a complete
distribution of the colouring matter upon the pulp, with the result
that the intensity of colour is increased, its fastness strengthened,
and the process of dyeing generally rendered more economical. This is
effected by the judicious addition of a suitable acid dye to the pulp
already coloured with the basic dye.

The direct colouring matters have but a very limited application for
paper dyeing owing to their sensitiveness to acids and alkalies.

In the colouring of paper pulp, attention is given to many important
details, such as:--

_Fading of Colour._--Some loss of colour almost invariably occurs even
with dyes generally looked upon as fast to light. The shade or tint of
the paper is affected not only by exposure to light, but by contact of
the coloured paper with common boards on which it is often pasted. The
alkalinity of straw boards, for example, is frequently one source of
serious alteration of colour, and the acidity of badly made pastes and
adhesives another.

In all such cases, the dyes must be carefully selected in order to
obtain a coloured paper which will show a minimum alteration in tint
by exposure to light or by contact with chemical substances. This is
particularly necessary in coloured wrapping paper used for soap, tea,
cotton yarn, and similar goods.

_Unevenness of Colour._--The different affinity of the various
paper-making fibres for dyes is apt to produce an uneven colour in the
finished paper. This is very noticeable in mixtures of chemical wood
pulp or cellulose and mechanical wood pulp. The ligno-cellulose of
the latter has a great affinity for basic dyes, and if the required
amount of dye is added to a beater containing the mixed pulps in
an insufficiently diluted form, the mechanical wood pulp becomes
more deeply coloured than the cellulose. If the former is a finely
ground pulp, the effect is not very noticeable, but if it is coarse,
containing a large number of coarse fibres, then the paper appears
mottled. The defect is still further aggravated when the paper is
calendered, especially if calendered in a damp condition. In that case
the strongly coloured fibres of mechanical wood are very prominent.

When dyes have been carelessly dissolved and added to the beating
engine without being properly strained, unevenness of colour may often
be traced to the presence of undissolved particles of dye.

_Irregular Colour of the two Sides._--Many papers exhibit a marked
difference in the colour of the two sides. When heavy pigments are
employed as the colouring medium, the under side of the sheet, that is,
the side of the paper in contact with the machine wire, is often darker
than the top side. The suction of the vacuum boxes is the main cause
of this defect, though the amount of water flowing on to the wire, the
"shake" of the wire, and the extent to which the paper is sized are all
contributory causes. By careful regulation of these varying conditions
the trouble is considerably minimised.

The under surface of the paper is not invariably darker than the top
surface. With pigments of less specific gravity the reverse is found to
be the case. This is probably to be explained by the fact that some of
the colouring matter from the under side is drawn away from the paper
by the suction boxes, and the pigment on the top side is not drawn away
to any serious extent, because the layer of pulp below it acts as a
filter and promotes a retention of colour on the top side.

It is interesting to notice that this irregularity sometimes occurs
with soluble dyes, as for example in the case of auramine. The
decomposition of this dye when heated to the temperature of boiling
water is well known, and the contact of a damp sheet of paper coloured
by auramine with the surfaces of steam-heated cylinders at a high
temperature brings about a partial decomposition of the dye on one side
of the paper. Generally speaking, acid dyes are more sensitive to heat
than basic dyes.

The presence of china clay in a coloured paper is also an explanation
of this irregular appearance of the two sides. China clay readily forms
an insoluble lake with basic dyes, and when the suction boxes on the
machine are worked with a high vacuum the paper is apt to be more
deeply coloured one side than another.

_The Machine Backwater._--Economy in the use of dyes to avoid a loss
of the colouring matter in the "backwater," or waste water from the
paper machine, is only obtained by careful attention to details of
manufacture on the one hand and by a knowledge of the chemistry of
dyeing on the other. The loss is partly avoided by regulating the
amount of water used on the machine, so that very little actually goes
to waste, and further reduced by ensuring as complete a precipitation
of the soluble dye as possible.

The _acid_ dyes generally do not give a colourless backwater, and all
pulps require to be heavily sized when acid dyes are used.

The _basic_ dyes are more readily precipitated than the acid dyes,
particularly if a suitable mordant is used, even with heavily coloured
papers. The addition of an acid dye to pulp first coloured with a basic
dye is frequently resorted to as a means of more complete precipitation.

_Dyeing to Sample._--The matching of colours has been greatly
simplified through the publication of pattern books by the firms who
manufacture dyes, in which books full details as to the composition
of the paper, the proportion of colour and the conditions for maximum
effects are fully set out. The precise results obtained by treating
paper pulp with definite proportions of a certain dye, or a mixture
of several dyes, is determined by experimental trials. A definite
quantity of moist partially beaten and sized pulp, containing a known
weight of air-dry fibre, is mixed with a suitable volume of water at a
temperature of 80° to 90° F. and the dye-stuff added from a burette in
the form of a 1 per cent. solution. If preferred a measured volume of
a 1 per cent. solution of the dye can be placed in a mortar, and the
moist pulp, previously squeezed out by hand, added gradually and well
triturated with the pestle.

The dyed mixture is then suitably diluted with water, made up into
small sheets of paper on a hand mould or a siphon mould, and dried.

The effect of small additions of colour to the contents of a beating
engine is frequently examined in a rough and ready way by the
beaterman, who pours a small quantity of the diluted pulp on the edge
of the machine wire while the machine is running. This gives a little
rough sheet of paper very quickly.

The comparison of the colour of a beaterfull of pulp with the sample
paper which it is desired to match is also effected by reducing a
portion of the paper to the condition of pulp, so that a handful of the
latter can be compared with a quantity of pulp from the engine. This is
not always a reliable process, especially with papers coloured by dyes
which are sensitive to the heat of the paper machine drying cylinders.

_Detection of Colours in Papers._--The examination of coloured papers
for the purpose of determining what dyes have been employed is a
difficult task. With white papers which have been merely toned the
proportion of dye is exceedingly small, and a large bulk of paper has
to be treated with suitable solvents in order to obtain an extract
containing sufficient dye for investigation.

With coloured papers dyed by means of pigments, the colour of the
ash left on ignition is some guide to the substance used, a red ash
indicating iron oxide, a yellow ash chromate of lead, and so on.

With papers dyed by means of coal tar colours the nature of the
colouring matter may be determined by the methods of analysis employed
for the examination of textile fibres.

The following hints given by Kollmann will be found useful:--

Tear up small about 100 grammes of paper, and boil it in alcohol, in
a flask or a reflux condenser. This must be done before the stripping
with water, so as to extract the size which would otherwise protect
the dye from the water. Of course the alcohol treatment is omitted
with unsized paper. The paper is now boiled with from three to five
lots of water, taking each time only just enough to cover the paper.
This is done in the same flask after pouring off any alcohol that
may have been used, and also with the reflux condenser. The watery
extract is mixed with the alcohol extract (if any). Three cases may
occur:--(1) The dye is entirely stripped, or very nearly so. (2) The
dye is partly stripped, what remains on the fibres showing the same
colour as at first or not. (3) The dye is not stripped. To make sure
of this the solution is filtered, as the presence in it of minute
fragments of fibre deceive the eye as to the stripping action. In the
first two cases the mixed solutions are evaporated down to one half on
the water bath, filtered, evaporated further, and then precipitated by
saturating it with common salt. The dye is thrown out at once, or after
a time. It may precipitate slowly without any salt. The precipitated
dye is filtered off and dried. To see whether it is a single dye or a
mixture, make a not too dark solution of a little of it in water, and
hang up a strip of filter paper so that it is partly immersed in the
solution. If the latter contains more than one dye they will usually
be absorbed to different heights, so that the strip will show bands of
different colours crossing it. If it is found that there is only one
dye, dissolve some of it in as little water as possible, and mix it
with "tannin-reagent," which is made by dissolving equal weights of
tannin and sodium acetate in ten times the weight of either of water.
If there is a precipitate there is a basic dye, if not, an acid dye.
In the former case mix the strong solution of the dye with concentrated
hydrochloric acid and zinc dust, and boil till the colour is destroyed.
Then neutralise exactly with caustic soda, filter, and put a drop of
the filtrate on to white filter paper. If the original colour soon
reappears on drying, we draw the following conclusions:--

(_a_) The colour is red; the dye is an oxazine, thiazine, azine, or
acridine dye, _e.g._, safranine. (_b_) It is orange or yellow; the dye
is as in (_a_), _e.g._, phosphine. (_c_) It is green; the dye is as in
(_a_), _e.g._, azine green. (_d_) It is blue; the dye is as in (_a_),
_e.g._, Nile blue, new blue, fast blue, or methylene blue. (_e_) It
is violet; the dye is as in (_a_), _e.g._, mauveine. If the original
colour does not reappear on drying, but does so if padded with a 1 per
cent. solution of chromic acid, we draw the following conclusions:--

(_a_) The colour is red; the dye is rhodamine or fuchsine, or one of
their allies. (_b_) It is green; the dye is malachite green, brilliant
green, or one of their allies. (_c_) It is blue; the dye is night blue,
Victoria blue, or one of their allies. (_d_) It is violet; the dye is
methyl violet, crystal violet, or one of their allies.

If the original colour does not reappear even with chromic acid, it was
in most cases a yellow or a brown, referable to auramine, chrysoidine,
Bismarck brown, thioflavine, or one of their allies.

If the tannin reagent produces no precipitate, reduce with hydrochloric
acid and zinc, or ammonia and zinc, and neutralise and filter as in the
case of a basic dye. The solution when dropped on to white filter paper
may be bleached (_a_), may have become a brownish red (_b_), may have
been imperfectly and slowly bleached (_c_), or may have undergone no
change (_d_).

(_a_) If the colour quickly returns the dye is azurine,
indigo-carmine, nigrosine, or one of their allies. If it returns only
on padding with a 1 per cent. solution of chromic acid, warming, and
holding over ammonia, some of the dye is dissolved in water mixed
with concentrated hydrochloric acid, and shaken up with ether. If the
ether takes up the dye, we have aurine, eosine, erythrine, phloxine,
erythrosine, or one of their allies. If it does not, we have acid
fuchsine, acid green, fast green, water blue, patent blue, or one
of their allies. If the colour never returns, heat some of the dye
on platinum foil. If it deflagrates with coloured fumes, the dye is
aurantia, naphthol yellow S., brilliant yellow, or one of their allies.
If it does not deflagrate, or very slightly, dissolve a little of the
dye in one hundred times its weight of water, and dye a cotton skein
in it at the boil for about fifteen minutes. Then rinse and soap the
skein vigorously. If the dyeing is fast with this treatment we have a
substantive cotton yellow or thiazine red; if it is not, we have an
ordinary azo dye. (_b_) The dye is an oxyketone, such as alizarine.
(_c_) The dye is thiazol yellow, or one of its allies. (_d_) The dye is
thioflavine S., quinoline yellow, or one of their allies.

If the dye is not stripped by alcohol and water, it is either inorganic
or an adjective dye, such as logwood black, cutch, fustic, etc.; and we
proceed according to the colour as follows:--

If it is red or brown, the dyed fibre is dried and divided into two
parts. One is boiled with bleaching powder. If it is bleached entirely
or to a large extent, the dye is cutch. If the bleach has no action,
incinerate some of the dyed fibre in an iron crucible and heat the
ash on charcoal before the blowpipe. If a globule of lead is formed,
we have saturn red. The second portion is boiled with concentrated
hydrochloric acid. If there is no action, we have Cologne umber; if
there is partial action, we have real umber; if the dye dissolves
completely to a yellow solution, we have an ochre; if the solution is
colourless instead of yellow, and chlorine is evolved during solution,
we have manganese brown.

If the colour is yellow or orange, boil with concentrated hydrochloric
acid. If we get a green solution and a white residue, we infer chrome
yellow or orange. If we get a yellow solution, we boil it with a drop
or two of nitric acid and then add some ammonium sulphocyanide. A red
colour shows an ochre or Sienna earth.

If the colour is green, boil with caustic soda lye. If the fibre turns
brown, we have chrome green. If no change takes place, boil with
concentrated hydrochloric acid. A yellow solution shows green earth; a
red colour logwood plus fustic.

If the colour is blue or violet, boil with caustic soda lye. If the
fibre turns brown, we have Prussian blue. If no change takes place,
boil with concentrated hydrochloric acid. A yellow solution shows
smalts. If the colour is destroyed, and the smell of rotten eggs is
developed, we have ultramarine.

If the colour is black, warm with concentrated hydrochloric acid
containing a little tin salt. If the black is unchanged, we have a
black pigment. If we get a pink to deep red solution we have logwood
black.

By means of the tests above detailed at length the group to which the
dye belongs is discovered, and often the actual dye itself. Once the
group is known it is generally easy, by means of the special reactions
given in many books, _e.g._, in Schultz and Julius's "Tabellarische
Übersicht," to identify the particular dye.

When one has to deal with a single dye and simply desires to
determine its group, the following table, due to J. Herzfeld, will
suffice. Originally intended for textiles, it will serve, with some
modifications here made in it, for the rapid testing of paper.


1.--RED AND REDDISH BROWN DYES.

Boil the paper with a mixture of alcohol and sulphate of alumina. If
no dye is extracted or a fluorescent solution is formed, we have an
inorganic pigment, or eosine, phloxine, rhodamine, safranine, or one
of their allies. Add bleaching powder solution, and heat. If the paper
is bleached, add concentrated hydrochloric acid. A violet colour shows
safranine or an analogue. If there is no colour, but the fluorescence
disappears, we have eosine, phloxine, rhodamine, or one of their
allies. If the paper is not bleached test for inorganic colouring
matters. Cutch brown is partly but not entirely bleached.

If the alumina solution gives a red or yellow solution without
fluorescence, add to it concentrated sodium bisulphite. If bleaching
takes place, heat a piece of the paper with dilute spirit. A red
extract shows sandal wood, fuchsine, etc. If there is little or no
extract, we have acid fuchsine or one of its allies. If the bisulphite
causes no bleaching, boil a piece of the paper with very dilute
hydrochloric acid. If the colour is unchanged, heat another piece of
the paper with dilute acetate of lead. If no change takes place, we
have an azo dye. If the colour turns to a dark brownish red, we have
cochineal or the like. If the boiling with very dilute hydrochloric
acid darkens the colour we have a substantive cotton dye.


2.--YELLOW AND ORANGE DYES.

Heat some of the paper with a not too dilute solution of tin salt in
hydrochloric acid. If the colour is unchanged, with a colourless or
yellow solution, boil some more paper with milk of lime. A change to
reddish or brown shows turmeric or a congener. Absence of change shows
phosphine, quinoline yellow, or a natural dye-stuff. If the acid tin
solution turns the paper red, and then quickly bleaches it to a pale
yellow, we have fast yellow, orange IV., metanil yellow, brilliant
yellow, or the like. If the tin turns the paper greyish, heat another
portion with ammonium sulphide. A blackening shows a lead or iron
yellow. If there is no change, we have naphthol yellow, auramine,
azoflavine, orange II., chrysoidine, or one of their allies.


3.--GREEN DYES.

Heat a sample of the paper in dilute spirit. If the spirit acquires
no colour, warm for a short time with dilute sulphuric acid. If both
paper and solution become brownish red, we have logwood plus fustic. If
this fails, boil with concentrated hydrochloric acid. A yellow solution
shows green earth. If this fails, boil with concentrated caustic soda.
Browning shows chrome green. If the spirit becomes blue, it is a case
of paper which has been topped with blue on a yellow, brown, or green
ground. The solution and the insoluble part are separately tested. The
case is probably one of an aniline blue dyed over a mineral pigment. If
the spirit becomes green, heat with dilute hydrochloric acid. If the
fibre is completely or nearly bleached, and the acid turns yellow, the
dye is brilliant green, malachite green, or one of their allies.


4.--BLUE AND VIOLET DYES.

Heat some of the paper with dilute spirit. If the alcohol remains
colourless, we have Prussian blue or ultramarine. If it becomes blue
or violet, shake some of the paper with concentrated sulphuric acid.
A dirty olive green shows methylene blue, and a brownish colour shows
spirit blue, water blue, Victoria blue, methyl violet, etc. If the
spirit turns yellow, and the colour of the paper changes, we have wood
blue or wood violet.




CHAPTER XI

PAPER MILL MACHINERY


In the case of common printings and writings, which form the great
bulk of the paper made, the possibility of one mill competing against
another, apart from the important factor of the cost of freight, coal,
and labour, is almost entirely determined by the economy resulting from
the introduction of modern machinery.

The equipment of an up-to-date paper mill, therefore, comprises all
the latest devices for the efficient handling of large quantities of
raw material, the economical production of steam, and the minimum
consumption of coal, matters which are of course common to most
industrial operations, together with the special machinery peculiar to
the manufacture of paper.

The amount of material to be handled may be seen from the table on page
215, which gives the approximate quantities for the weekly output of a
common news and a good printing paper.

_Economy in Coal Consumption._--The reduction to a minimum of the
amount of coal required for a ton of paper has been brought about by
the use of appliances for the better and more regular combustion of
the coal, such as mechanical stokers, forced and induced draught, the
introduction of methods for utilising waste heat in flue gases by
economisers, and the waste heat in exhaust steam and condensed water
by feed-water heaters, the adoption of machines for securing the whole
energy of the live steam by means of superheaters, adequate insulation
of steam mains and pipes, high pressure boilers, and engines of most
recent design.

The firing of steam boilers is now conducted on scientific principles,
the coal being submitted regularly to proper analysis for calorific
value, the evaporative power of the boilers being determined at
intervals by adequate trials, the condition of the waste flue gases
being automatically

TABLE SHOWING THE MATERIALS REQUIRED FOR NEWS AND PRINTINGS.

  -----------------------------+--------------+------------------
             --                |  Common News.|  Good Printings.
  -----------------------------+---------------+-----------------
  Weekly output of paper, say  |    600 tons   |    250 tons
  Mechanical wood pulp, moist, |               |
     50 per cent. dry          |    800  "     |      Nil.
  Chemical wood pulp, dry      |    200  "     |    150 tons
  Esparto                      |     Nil.      |    200  "
  Soda ash                     |     Nil.      |     16  "
  Coal                         |    600 tons   |    800  "
  Lime                         |     Nil.      |     45  "
  China clay                   |     60 tons   |     25  "
  Bleach                       |     Nil.      |     30  "
  Alum, rosin, and chemicals   |     20 tons   |     20  "
  Water, per ton paper         |  8,000 gallons| 40,000 gallons
  -----------------------------+---------------+-----------------

_The Sarco Combustion Recorder._--This instrument is a device which
automatically records the percentage of carbonic acid gas in the waste
gases from boiler furnaces. The flue gases are analysed at frequent
and regular intervals, and the results of the analysis can be seen on
a chart immediately, so that it is possible to determine the effect of
an alteration in the firing of the boilers within two minutes of its
taking place. The apparatus is rather complicated, but the principle
upon which it is based is simple.

Measured quantities of the flue gases are drawn into graduated glass
tubes and brought into contact with strong caustic soda solution, which
absorbs all the carbonic acid gas. The remaining gases not absorbed
by the caustic soda are automatically measured and the percentage of
carbonic acid gas registered on the chart.

The use of suitable boiler feed-water is also an important factor in
modern steam-raising plant. The hot condensed water from the paper
machine drying cylinders, and exhaust steam from the engines and
steam-pipes, is returned to the stoke-hole to be utilised in heating up
the cold water which has been previously softened by chemical treatment.

[Illustration: FIG. 55.--Conventional Diagram of a Water Softening
Plant.

  A.  Water supply.
  B.  Regulating tank.
  C.  Lime mixer.
  D.  Soda tank.
  E.  Settling tank and filter.
  F.  Outlet for softened water.
]

_Water Softening._--The water softeners available on the market are
numerous, and as each possesses special advantages of its own, it would
be almost invidious to select any one for particular notice.

They are based upon the principle of mixing chemicals with the water
to be treated, so as to precipitate the matters in solution and
give a boiler feed-water free from carbonates and sulphates of lime
and magnesia. The chemicals are added in the form of solutions of
carefully regulated strength to the water, which flow in a continuous
stream into a tank. The flow of the water and chemical reagent is
adjusted by previous analysis.

The various machines differ in details of construction, and in the
methods by which the mixing of the water and reagents is effected. The
object to be achieved is the complete precipitation of the dissolved
salts and the production of a clear water, free from sediment, in an
apparatus that will treat a maximum quantity of water at a cheap rate
per 1,000 gallons.

The process needs proper attention. The addition of reagents in
wrong proportions will do more harm than good, and possibly result
in hardening the water instead of softening it. The following may be
quoted as an example:--

  ----------------------+-----------+-----------+------------
  Composition of Water. |  Before   |  After    |  Change.
                        | Treatment.| Treatment.|
  ----------------------+-----------+-----------+------------
  Calcium carbonate     |   13·863  |   38·920  | 25·057 gain
  Calcium oxide (lime)  |    0·0    |   14·300  | 14·300  "
  Calcium silicate      |    2·062  |    3·591  |  1·529  "
  Calcium sulphate      |    1·625  |    2·121  |  0·496  "
  Magnesia              |    0·0    |    0·266  |  0·266  "
  Ferric oxide, etc.    |    0·447  |    0·987  |  0·540  "
                        +-----------+-----------+------------
   Scale forming mineral|   17·997  |   60·185  | 42·188 gain
                        +-----------+-----------+------------
  Calcium chloride      |    1·331  |    2·114  |  0·783 gain
  Magnesium chloride    |    0·672  |    0·0    |  0·672 loss
  Sodium chloride       |    0·478  |    0·476  |  0·003  "
                        +-----------+-----------+------------
   Soluble salts        |    2·482  |    2·590  |  0·108 gain
                        +-----------+-----------+------------
   Total mineral matter |   20·479  |   62·776  | 42·297 gain
                        +-----------+-----------+------------
  Carbonic acid gas     |    9·71   |    0·0    |  9·71  loss
  Oxygen gas            |    0·66   |    0·66   |  0·0    "
  ----------------------+-----------+-----------+------------

  Treatment required: 1·8 lbs. of lime, 0·2 lbs. soda ash per 1,000
      gallons. Apparently 5·5 lbs. of lime were being used and no soda
      (Stromeyer).

_Superheated Steam._--The effective application of the energy of the
high pressure steam is probably one of the most important problems in
paper mill economy. The use of superheated steam is being extended
in every direction, and, in addition to the advantages obtained in
the steam engine itself, its wider possibilities for the boiling of
esparto, wood, and fibres generally have been noted. The following case
may be quoted as the result of a trial at a paper mill, showing for
stated conditions the advantages of superheated steam:--

    --------------------------+-------------+----------
               --             | Superheated | Ordinary
                              |    Steam.   |  Steam.
    --------------------------+-------------+----------
    Duration of test hours    |     26      |    34
                              |             |
    Coal consumed (lbs.)--    |             |
      Per hour                |    610·5    |   661·5
      Per 1 h.-p. hour        |      1·83   |     2·08
                              |             |
    Water evaporated (lbs.)-- |             |
      Per hour                |  4,832      | 5,679
      Per 1 h.-p. hour        |     14·55   |    17·8
      From and at 212° F.     |      8·7    |     8·94
                              |             |
    Steam, temperature F.     |    464      |   334
      Pressure                |     90·3    |    90·8
                              |             |
    Steam engine--            |             |
      1 h.-p. total           |    331·5    |   323·2
      Temperature F.          |    381·8    |   333·8
                              |             |
    Coal used per 1 h.-p.--   |             |
      Per hour at boiler      |      1·83   |     2·08
    --------------------------+-------------+----------

This appears to show a saving of 12 per cent.

_Gas Producers._--The substitution of gas for steam in the paper mill
has not yet proved a success. The fact that heat is required for the
drying cylinders of a paper machine, and that the heat is most cheaply
and readily obtained in the form of exhaust steam from the engines
driving the paper machine, militates considerably against economies
which might otherwise be possible. The difficulties of heating such
cylinders, or rather of properly controlling and regulating the
temperature by any other means than steam, may easily be surmised.

Gas engines of over 200 h.-p. seem to give considerable trouble at
present, but no doubt in course of time the required improvements will
be effected.

It is generally supposed that gas producers can only be economical
when utilised for the production of gas on a large scale, and for
distribution to engines of smaller capacity than the main steam engine
required in a paper mill. The peculiar conditions of the manufacture
of paper do not appear to be favourable to the adoption of the gas
producer system in its present form.

_Motive Power._--The paper-maker has taken advantage of every modern
improvement in steam engines for the purpose of reducing the cost of
motive power. Amongst other alterations in this direction the use of
a high speed enclosed engine and the employment of the modern steam
turbine may be noted.

In the enclosed engine the working parts are boxed in by a casing
fitted with oil-tight doors. The cranks and connecting rods splash into
the oil, which is thus thrown about in all directions, so as to ensure
sufficient lubrication. Another feature of this engine is the variable
speed, and it is possible to run the paper machine at speeds varying
from 100 to 500 ft. per minute without the use of change wheels.

_Electrical Driving._--The application of electricity for motive power
has made steady advances in the paper mill. At first it was limited
to the driving of machinery in which variations of speed or load were
not required to any large extent, but of recent years beating engines,
calenders, and paper machines have all been fitted with electrical
drives.

[Illustration: FIG. 56.--An "enclosed" Steam Engine.]

The following details relate to the installation at the Linwood Paper
Mills:--

The installation consists of 250-K.W. steam dynamos. The engines are
Willan's high speed triple expansion, working with a boiler pressure of
250 lbs. per square inch at the stop valve, the steam being superheated
to give a temperature of 500° Fahr. at the engine. By means of jet
condensers a vacuum of 25 to 25½ inches is obtained on the engines.
The two boilers are of the Babcock type, and have 3,580 square feet of
heating surface each. The furnaces have chain grate stokers, and the
boilers are arranged with their own superheaters. The motor equipment
consists of eight 80, two 50, and ten 25 B.H.P. motors.

Six of the 80 B.H.P. drive the beating engines, and it has been found
that the motors readily respond to an overload of 50 per cent. without
beating or other trouble. To remedy the excessive and sudden variation
a belt drive was adopted. An 80 motor drives the pulp refining engine.
The two paper-making machines have each two motors, one a 25 and a 50
and the other two 25 B.H.P. motors. The speed can be regulated with
exactitude. The auxiliary plant of the paper-making machine, pumps,
agitators, etc., is worked from lines of shafting driven by motors.

Calender motors are of the variable speed type, being designed to
run from 100 revolutions per minute to 600 revolutions per minute.
Variations from 300 to 600 revolutions per minute can be regulated by
the shunts, the loss being negligible. Several of the motors are geared
up to the various machines, as is the case with the calender.

As regards cost, the capital outlay on the 500-K.W. generating plant,
including engines, dynamos, boilers, condensers, steam pipes, filters,
etc., and all engine room accessories, was £9,500.

[Illustration: FIG. 57.--An Electrically Driven Paper Machine.]

In addition to the above, the plant also contains a Parson's steam
turbine of 1,000 K.W., driving two continuous current dynamos.

[Illustration: FIG. 58.--Diagram of the "Eibel" Process.]

_The Eibel Patent._--One of the most important improvements in
connection with the manufacture of newspaper is the Eibel process,
designed to increase the speed of the machine and to reduce the amount
of suction at the vacuum box. In the ordinary machine the wire has
usually been arranged to move in a horizontal plane. In some machines
means have been provided for adjusting the breast-roll end of the wire
to different elevations to provide for dealing with different grades
of stock, but the wire has never hitherto been so inclined as to cause
the paper stock to travel at a speed, under the action of gravity, to
equal or approximate the speed of the wire. In all previous methods
of working, the wire has for a considerable portion of its length,
starting from the breast-roll, drawn the stock along in consequence of
the wire moving much faster than the stock, and the stock has waved, or
rippled, badly near the breast-roll end of the wire. This has gradually
diminished until an equilibrium has been established and an even
surface obtained, but not until the waving or rippling has ceased at
some considerable distance from the breast-roll have the fibres become
laid uniformly, and the machines have therefore necessarily been run
slowly to give ample time for the water to escape and for the fibres
to lie down so as to make them a uniform sheet. In many cases the
breast-roll has been raised 14 or 15 inches, and the stock rushes, as
it were, downhill.

As, during the formation of the paper, the stock and the wire
practically do not move relatively to each other, there is no drag
of the stock upon the wire; consequently there is a more rapid and
uniform drainage of the water from the stock, the full influence of the
"shake" is made effective to secure uniformity in the distribution and
interlocking of the fibres, and the regularity of the formation of the
paper is not disturbed by waves or currents, which would otherwise be
caused by pull of the wire upon the stock.

This ingenious device is now working successfully in many paper mills.

_Machinery._--In setting out the plant necessary for a paper mill
which is designed to produce a given quantity of finished paper, the
manufacturer takes into consideration the class of paper to be made
and the raw material to be employed. The following schedule has been
prepared on such a basis:--


PLANT AND MACHINERY FOR HIGH-CLASS PRINTINGS.

_Paper._

    High-class printings made of wood pulp and esparto, used alone or
      blended in varying proportions as required. Quantity, 250 tons
      weekly.

_Raw Material._

    Esparto; chemical wood pulp.

    Quantity: esparto, about 200 tons; wood pulp, 150 to 160.

    China clay and usual chemicals.

In the estimation of materials required for the production of about
250 tons of paper, it is assumed that the 200 tons of esparto fibre
will yield 90 tons bleached esparto fibre, and that the mechanical
losses which take place during manufacture are counterbalanced by the
weight of china clay added to the pulp. These conditions naturally vary
in different mills, but such variations do not affect the schedule of
machinery.

_Unloading Sheds._

    2 steam or electric cranes for handling fibre, clay, alum, bleach,
      rosin, coal, and finished paper.

    1 3-ton weighbridge.

    1 5-cwt. platform scales.

_Steam Plant._

    6 8-ft. by 30-ft. Lancashire boilers.

    Fuel economiser.

    Feed-water pump and tank.

    Water softening apparatus.

    1 500-h.-p. main steam engine, for fibre departments and beater
      floor.

_Chemical Department._

    Hoist for clay, alum, bleach, lime, &c.

    4 causticising pans, 9 ft. diameter, 9 ft. deep.

    2 storage tanks.

    2 chalk sludge filter presses.

    2 clay-mixing vats, 6 ft. diameter, 6 ft. deep.

    1 starch mixer, 6 ft. diameter, 6 ft. deep.

    1 size boiler, 8 ft. diameter, 8 ft. deep.

    3 size storage tanks, 1,000 gallons each.

    3 bleach-mixing vats.

    3 bleach liquor settling tanks.

    2 clear bleach liquor storage tanks.

    1 alum dissolving tank.


_Recovery Department_:--

      _Soda._

    1 multiple effect evaporating plant.

    1 rotary furnace.

    4 lixiviating tanks, 2,000 gallons each.

    2 storage tanks for clear liquor from lixiviating tanks, 20,000
      gallons capacity.

      _Fibre._

    2 tanks for receiving machine backwater.

    2 Fullner's stuff catchers, or some other system of treating
      backwater.

    2 filter presses.


_Esparto Department._

    1 esparto duster.

    Travelling conveyer for cleaned esparto.

    6 Sinclair vomiting boilers, each of 3 tons capacity.

    2 measuring tanks for caustic liquor.

    4 washing engines, 15 cwt. capacity.

    6 Tower bleaching engines.

    1 presse-pâte.

    10 galvanised iron trucks.


_Wood Pulp Department._

    4 pulp disintegrators and pumps.

    4 Tower bleaching engines.

    4 washing tanks or drainers.

    6 galvanised iron trucks.


_Beater Floor._

    8 1,200-lbs. beating engines.

    2 Marshall refiners.

    6 galvanised iron trucks.


_Paper Machine Room._

    2 paper machines, 106 in. wide, with stuff chests, strainers, and
      engines complete.

    1 paper machine, 120 in. wide, with stuff chests, strainers, and
      engines complete.

    Patent dampers for each machine.


_Calendering Room._

    2 110-in. supercalenders.

    2 100-in. supercalenders.

    2 6-reel cutters.

    1 200-h.-p. main steam engine.


_Finishing Room._

    Sorting tables.

    Packing press.

    Weighing machine.


_Repairs Department._

    Usual repair outfit, such as lathes, planing machine, drilling
      tools, etc.

    Blacksmith's shop outfit.

    Carpenter's shop outfit.

    Calender roll grinder.


_Water Supply._

    Main storage tank, 50,000 gallons capacity.

    Water pumps.

    Piping and connections to various departments.

    Bell's patent filters (if necessary).




CHAPTER XII

THE DETERIORATION OF PAPER


Recent complaints about the quality of paper and the rapid decay of
manuscripts and papers have resulted in arousing some interest in the
subject of the durability of paper used for books and legal documents,
and in the equally important question of the ink employed. The Society
of Arts and the Library Association in England and the Imperial Paper
Testing Institute in Germany have already appointed special committees
of inquiry, and from this it is evident that the subject is one of
urgent importance.

It is sometimes argued that the lack of durability is due to the want
of care on the part of manufacturers in preserving the knowledge of
paper-making as handed down by the early pioneers, but such an argument
is superficial and utterly erroneous. The quality of paper, in common
with the quality of many other articles of commerce, has suffered
because the demand for a really good high-class material is so small.
The general public has become accustomed to ask for something cheap,
and since the reduction in price is only rendered possible by the use
of cheap raw material and less expensive methods of manufacture, the
paper of the present day, with certain exceptions, is inferior to that
of fifty years ago.

The causes which favour the deterioration of paper are best understood
by an inquiry into the nature of the fibres and other materials used
and the methods of manufacture employed.

_The Fibres Used._--Cotton and linen rags stand preeminent amongst
vegetable fibres as being the most suitable for the production of
high-class paper capable of withstanding the ravages of time. This
arises from the fact that cotton and linen require the least amount
of chemical treatment to convert them into paper pulp, since they are
almost pure cellulose, cotton containing 98·7 per cent. of air-dry
cellulose, and flax 90·6 per cent. The processes through which the raw
cotton and flax are passed for the manufacture of textile goods are
of the simplest character, and the rags themselves can be converted
into paper without chemical treatment if necessary. As a matter of
fact certain papers, such as the O. W. S. and other drawing papers,
are manufactured from rags without the aid of caustic soda, bleach, or
chemicals. The rags are carefully selected, boiled for a long time in
plain water, broken up and beaten into pulp, and made up into sheets by
purely mechanical methods.

The liability of papers to decay, in respect of the fibrous
composition, is almost in direct proportion to the severity of
the chemical treatment necessary to convert the raw material into
cellulose, and the extent of the deviation of the fibre from pure
cellulose is a measure of the degradation which is to be expected. The
behaviour of the fibres towards caustic soda or any similar hydrolytic
agent serves to distinguish the fibres of maximum durability from
those of lesser resistance. It may be noted that in the former the
raw materials, viz., cotton, linen, hemp, ramie, etc., contain a high
percentage of pure cellulose, while in the latter the percentage of
cellulose is very much lower, such fibres as esparto, straw, wood,
bamboo, etc., giving only 40-50 per cent. of cellulose. The two
extremes are represented by pure cotton rag and mechanical wood pulp.
Other things being equal, the decay which may take place in papers
containing the fibre only, without the admixture of size or chemicals,
may be considered as one of oxidation, which takes place slowly in
cotton, and much more rapidly with mechanical wood pulp. Experimental
evidence of this oxidation is afforded when thin sheets of paper made
from these materials are exposed to a temperature of 100° to 110° C.
in an air oven. The cotton paper is but little affected, while the
mechanical wood pulp paper soon falls to pieces.

The order of durability of various papers in relation to the fibrous
constituents may be expressed thus: (1) rag cellulose; (2) chemical
wood cellulose; (3) esparto, straw, and bamboo celluloses; (4)
mechanical wood pulp. The rate and extent of oxidation is approximately
shown by the effect of heat as described. The differences between
the celluloses are also shown by heating strips of various papers in
a weak solution of aniline sulphate, which has no effect on wood or
rag cellulose, dyes esparto and straw a pinkish colour, and imparts a
strong yellow colour to mechanical wood pulp and jute.

_Physical Qualities._--The permanence of a paper depends not only upon
the purity of the fibrous constituents and the freedom from chemicals
likely to bring about deterioration, but also upon the general physical
properties of the paper itself. Other things being equal, the more
resistant a paper is to rough usage the longer will it last. The reason
why rag papers are so permanent is that not only is the chemical
condition of the cellulose of the highest order, but the physical
structure of the fibre is such that the strength of the finished paper
is also a maximum.

The methods of manufacture may be modified to almost any extent, giving
on the one hand a paper of extraordinary toughness, or on the other
hand a paper which falls to pieces after a very short time. Thus a
strong bank-note paper may be crumpled up between the fingers three
or four hundred times without tearing, while an imitation art paper is
broken up when crumpled three or four times.

A thorough study of the physical qualities of a paper is therefore
necessary to an appreciation of the conditions for durability. The
physical structure of the fibre, the modifications produced in it by
beating, the effect of drying, sizing, and glazing upon the strength
and elasticity of the finished paper, are some of the factors which
need to be considered.

_Strength._--The strength of a paper as measured by the tensile strain
required to fracture a strip of given width, and the percentage of
elongation which the paper undergoes when submitted to tension, are
properties of the utmost importance. The elasticity, that is, the
amount of stretch under tension, has not received the attention from
paper-makers that it deserves. If two papers of equal tensile strength
differ in elasticity, it may be taken for granted that the paper
showing a greater percentage of elongation under tension is the better
of the two.

The strength of a paper, as already indicated, is greatly influenced by
the conditions of manufacture. This has been explained in the chapter
devoted to the subject of beating, and other examples are briefly given
in the following paragraphs.

_Bulk._--The manufacture during recent years of light bulky papers for
book production has accentuated the problem in a marked degree, and the
factor of _bulk_ as one of the causes of deterioration is therefore
a comparatively new one. It is interesting to notice that the rapid
destruction of such books by frequent use is in no way related to the
chemical purity of the cellulose of which it is composed, or to the
influence of any chemical substance associated with the fibre. It is
purely a mechanical question, to be explained by reference to the
process of manufacture.

This paper is made from esparto entirely, or from a mixture of esparto
and wood pulp. The pulp is beaten quickly, and for as short a time as
possible, little or no china clay being added, and only a very small
percentage of rosin size. The wet sheet of paper is submitted to very
light pressure at the press rolls, and the bulky nature is preserved by
omitting the ordinary methods of calendering.

The paper thus produced consists of fibres which are but little felted
together. The physical condition and structure of the paper are readily
noticeable to the eye, and when these peculiarities are reduced
to numerical terms the effect of the conditions of manufacture is
strikingly displayed.

The effect of this special treatment is best seen by contrasting the
bulky esparto featherweight paper with the normal magazine paper made
from esparto. In the latter case a smoother, heavier, stronger sheet
of paper is made from identically the same raw material. But the pulp
is beaten for a longer period, while mineral matter and size are added
in suitable proportions. The press rolls and calenders are used to the
fullest extent.

The difference between these two papers, both consisting, as they do,
of pure esparto with a small proportion of ash may be emphasised by
comparing the analysis by _weight_ with analysis by _volume_. The two
papers in question when analysed by weight proved to have the following
composition:--

      --------------------------------------------
                    |      Parts by Weight.
                    +----------------+------------
           --       | Featherweight. |  Ordinary.
      --------------+----------------+------------
      Esparto fibre |      96·0      |    95·4
      Ash, etc      |       4·0      |     4·6
                    |     -----      |   -----
                    |     100·0      |   100·0
      --------------+----------------+------------

But if the papers are compared in terms of the _composition by volume_,
it will be found that the featherweight contains a large amount of air
space.

      --------------+-----------------------------
                    |     Composition by Volume.
                    +----------------+------------
             --     | Featherweight. |  Ordinary.
      --------------+----------------+------------
      Esparto fibre |      28·0      |     65·5
      Ash, etc      |       0·7      |      1·8
      Air space     |      71·3      |     32·7
                    |     -----      |    -----
                    |     100·0      |    100·0
      --------------+----------------+------------

In other words, the conditions of manufacture for the bulky paper are
such that the fibres are as far apart from one another as possible, and
the cohesion of fibre to fibre is reduced to a minimum.

While paper of this description is agreeable to the printer, and
probably to the general reading public, yet its strength and physical
qualities, from the point of view of resistance to wear and tear, are
of the lowest order. It is very difficult to rebind books made from it,
which is not altogether to be wondered at, seeing that the bookbinder's
stitches can hardly be expected to hold together sheets containing 60
to 70 per cent. of air space.

This concrete case emphasises the necessity for including in a schedule
of standards of quality a classification of papers according to
strength and bulk.

_Surface._--The introduction of new methods of printing has brought
about some changes in the process of glazing and finishing paper which
are not altogether favourable to the manufacture of a sheet having
maximum qualities of strength and elasticity, two conditions which are
essential to permanence. In other words, the very high finish and
surface imparted to paper by plate-glazing, supercalendering, water
finish, and other devices of a similar character is carried to excess.

All papers are improved in strength by glazing up to a certain point,
but over-glazing crushes the paper, renders it brittle and liable to
crack. Unfortunately, the maximum strength of a paper is generally
reached before the maximum of finish, with the result that the former
is frequently sacrificed to the latter. The usual result of glazing
is found in an increase of 8 to 10 per cent. in the tensile strength,
but a diminution of elasticity to the extent of 8 to 10 per cent. With
supercalendered magazine papers, the high surface is imparted for the
sake of the illustrations which are produced by methods requiring it.
The addition of considerable quantities of clay or mineral substances
improves the finish, so that the question of the relation of glazing
to strength, surface, and loading is one which affects the subject of
deterioration of paper very materially. With writing paper the false
standard of an "attractive" appearance is almost universally accepted
by the public as the basis of purchase without any reference to actual
quality.

_Mineral Substances._--China clay, sulphate of lime, agalite and other
inert mineral substances are important factors in lowering the quality
of paper, not so much in promoting the actual deterioration of paper
by any chemical reaction with the fibres, as in making the paper less
capable of resistance to the influence of atmospheric conditions and
ordinary usage. Clay in small, well-defined quantities serves a useful
purpose, if added to some papers, because it favours the production
of a smooth surface, but when the combination of mineral substances
is carried to an extreme, then the result from the point of view of
permanence is disastrous. This is well recognised by all paper-makers,
and in Germany the limits of the amount of clay or loading in
high-grade paper have been rigidly fixed. In the case of _imitation
art_ paper, which contains 25 to 30 per cent. of its weight of clay,
the strength and resistance of the sheet is reduced to a minimum. The
paper falls to pieces if slightly damped, the felting power of the
fibres being rendered of no effect owing to the weakening influence of
excessive mineral matter. This paper is used chiefly for catalogues,
programmes, circulars, and printed matter of a temporary and evanescent
character, and so long as it is confined to such objects it serves
a useful purpose, being cheap, and suitable for the production of
illustrations by means of the half-tone process; but its lasting
qualities are of the lowest order. The addition of 10 per cent. of any
mineral substance must be regarded as the maximum allowance for papers
intended for permanent and frequent use.

_Coating Material._--The ingenious method for producing an absolutely
even surface on paper by the use of a mixture of clay or other mineral
substance and an adhesive like glue or casein brushed on to the surface
of the paper, is responsible for many of the complaints about the
papers of the present day.

The sole merit of this substance is the facility with which half-tone
process blocks can be utilised for the purpose of picture production.
Beyond this, nothing can be said. The paper is brittle, susceptible to
the least suspicion of dampness, with a high polish which in artificial
light produces fatigue of the reader's eye very quickly, heavy to
handle, and liable to fall to pieces when bound up in book form.

As the fibrous material is completely covered by mineral substances, it
is frequently considered of secondary importance, with the result that
the "value" of the paper is judged entirely by the surface coating,
with little regard to the nature of the body paper. In such cases, with
an inferior body paper, the pages of a book very quickly discolour, and
the letterpress becomes blurred.

  ANALYSIS OF A TYPICAL ART PAPER.

  ---------+-----------+-----------+------------
           | Per Cent. |           |   Volume
     --    |    by     |    --     | Composition
           |  Weight.  |           |  per Cent.
  ---------+-----------+-----------+------------
  Fibre    |    77·5   | Fibre     |    68·3
  Ash, etc.|    22·5   | Ash       |    12·0
           |           | Air space |    19·7
           |   -----   |           |   -----
           |   100·0   |           |   100·0
  ---------+-----------+-----------+------------

_Rosin._--The presence of an excess of rosin is a well-known factor in
the disintegration of the paper, even when the fibrous composition is
of the highest order. The decomposition is largely due to the action
of light, many experiments having been made by Herzberg and others to
determine the nature of the reactions taking place. One of the chief
alterations is the change brought about in the ink-resisting qualities
of the paper.

The actual character of the chemical reactions as far as the effect
on the fibre is concerned is not accurately known. The degradation
of a hard-sized rosin paper by exposure to strong sunlight, for
example, is probably due to the alteration in the rosin size, and not
to any material change in the cellulose. It is hardly conceivable
that in a pure rag paper sized with rosin and yielding readily to ink
penetration, after about one year's exposure to light, the cellulose
itself had undergone any chemical changes capable of detection.

_Gelatine._--Papers properly sized with gelatine are preferable
to those sized with rosin for the majority of books and documents
preserved under normal circumstances. But the nature of a tub-sized
paper may be, and often is, greatly altered by unusual climatic
conditions. In hot, damp countries papers are quickly ruined, and
high-class drawing papers sized with gelatine often rendered useless.
The change is scarcely visible on the clean paper, and is only observed
when the paper is used for water-colour work, the colour appearing
blotchy in various parts of the sheet where the gelatine has been
decomposed by the united action of heat and damp.

The artist is frequently compelled in such cases to put a layer of
heavy white colour on the sheet of paper before proceeding to paint the
picture.

The storage of books under favourable conditions has a great deal to
do with the permanence of the paper, and the degradation of a paper in
relation to the tub-sizing qualities is much hastened by the presence
of moisture in the air.

_Starch._--The same is true of starch, which is largely employed as
a binding or sizing material in paper. The degradation of gelatine,
starch, and similar nitrogenous substances is due to the action of
organisms, and the following experiments, suggested by Cross, are
interesting in this connection.

If strips of paper are put into stoppered bottles with a small quantity
of warm water and kept at a temperature of about 80° F., fungus
growths will be noticed on some of them after the lapse of fourteen
days. Rag papers sized with gelatine will show micro-organisms of all
kinds. A pure cellulose paper, like filter paper, will not produce any
such effects. The result in the first case is due to the nitrogenous
substance, viz., the gelatine used in sizing, since the two papers
are identical as far as the cellulose fibres are concerned. High-class
wood pulp papers, unless sized with gelatine, would not show similar
results. The action of the organisms upon the nitrogenous material by a
process of hydrolysis is in the direction of the production of soluble
compounds allied to the starch sugars capable of being assimilated by
organisms.

The cellulose of esparto and straw are readily attacked, and it is
on this account that the tissues of the various straws are digested
more or less when eaten by animals. It is for this reason that the
celluloses from straw and esparto are inferior to the cotton cellulose
in producing a paper likely to be permanent.

_Chemical Residues._--The necessity for manufacturing a pure cellulose
half-stuff is fully recognised by paper-makers. This was not the case
in the early days of the manufacture of wood pulp, for it is a matter
of common experience that many of the books printed on wood pulp paper
between 1870 and 1880 are in a hopeless condition, and it is quite easy
to find books and periodicals of that date the pages of which crumble
to dust when handled. This serious defect has been proved to be due to
the presence of traces of chemicals used in manufacture which have not
been thoroughly removed from the pulp.

The precautions necessary in bleaching pulp by means of chloride of
lime, in order to prevent (1) any action between the fibre and the
calcium hypochlorite, (2) the presence of residual chlorine or soluble
compounds derived from it, and (3) the presence of by-products arising
from the use of an antichlor, are also well known to paper-makers. The
subject has been closely studied by chemists, who have shown that the
deterioration of many modern papers may be ascribed to carelessness in
bleaching.

The questions relating to the chemical residues of paper can only be
adequately dealt with by a discussion of actual cases which arise from
time to time. There are certain conditions in manufacture, common to
all papers, which may give rise to the presence of chemical residues,
of which two have already been mentioned.

The acidity of papers is frequently quoted as an instance. It is true
that the presence of free acid in a paper is most undesirable, as it
seriously attacks the cellulose, converting it into an oxidised form.
This in course of time renders the paper so brittle as to destroy its
fibrous character.

The change is brought about by the acid, which itself suffers no
material alteration, so that the process of deterioration is continued
almost indefinitely until the cellulose is completely oxidised. Most
papers, however, show an acid reaction when tested with litmus, the
usual reagent employed by those not familiar with the proper methods
of testing paper. All papers which have been treated with an excess
of alum for sizing purposes would show an acid reaction with litmus
without necessarily containing any free acid.

The presence of iron is undesirable, particularly in photographic
papers, and since cellulose has a remarkable affinity for iron, the
conditions of manufacture which tend to leave iron in the pulp have to
be taken into consideration. The presence of minute quantities of iron
in the form of impurities must not be confused with the presence of
iron in large quantities derived from the toning and colouring of paper
by means of iron salts.

The fading of colour is frequently observed when coloured papers are
tested on boxboards, particularly those made of straw. This fading may
often be traced to the presence of alkali in the straw board which has
not been completely removed in the process of manufacture.

The blurring of letterpress is a defect which often occurs with
printing papers made of chemical wood pulp. The oil in the ink
seems to separate out on either side of the letter, producing a
discoloration. In such cases the paper itself frequently exhibits an
unpleasant smell.

These defects are usually determined by the presence of traces of
sulphur compounds in the paper resulting from incomplete washing of
the pulp in manufacture. The presence of sulphur compounds sometimes
associates itself with papers which have been coloured by means of
ultramarine, which in presence of alum is slightly decomposed by the
heat of the drying cylinders.

Some knowledge of the effect of chemical residues in paper is
important, not only in regard to the deterioration which takes place
in the fibre itself, but also in relation to the fading of the ink
which is used. The subject of the ink has received much attention
from chemists on account of the serious difficulties which have been
experienced by State departments in various countries.

The United States Department of Agriculture have devised certain
methods for ascertaining the suitability of stamping ink used by the
Government and suggest the qualities desirable in such an ink. The ink,
first of all, must produce an indelible cancellation; that is, it must
be relatively indelible as compared with the ink used for printing
the postage stamps. The post-mark made with the ink must dry quickly
in order that the mail matter may be handled immediately without any
blurring or smearing of the post-mark.

Both this property and the property of the indelibility involve the
question of the rate at which the ink penetrates or is absorbed by the
fibre of the paper. A satisfactory ink does not harden or form a crust
on the ink-pad on exposure to air. There must be no deposition of solid
matter on the bottom of the vessel in which the ink is stored, and the
pigments on which the indelibility of the ink depends, if insoluble,
must not settle out in such a way as to make it possible to pour off
from the top of the container a portion of the ink which contains
little or none of the insoluble pigment or pigments.

_Colour._--If the subject of deterioration of paper is to be considered
in its broadest sense as including changes of any kind, the fading of
colour must be taken into account. The use of aniline dyes which are
not fast to light results in a loss of colour in paper just as with
textiles, and the fading may be regarded as a function of the dye and
not as arising from its combination with the paper.

The gradual fading of some dyes, however, and of many water-colour
pigments may be traced to the presence of residual chemicals in the
paper and to the presence of moisture in an atmosphere impregnated
with gaseous or suspended impurities. In fact the latter is a greater
enemy to permanence of colour than light, since it has been proved by
experiment that most colours do not fade when exposed to light in a
vacuum. The oxygen of the air in combination with the moisture present
is the principal agent in bringing about such changes. The dulling
of bronze, or imitation gold leaf, on cover papers is a practical
illustration of this, though this can hardly be quoted as an instance
of actual deterioration of the paper.

The maintenance of the original colour can only be assured by the
careful selection of pure fibrous material, the use of fast dyes,
and the preservation of the book or painting from the conditions
which favour the fading as described above. For common papers such
precautions become impossible, but for water-colour drawings and
valuable papers they are essential.

The demand for an abnormally white paper is indirectly the cause of
deterioration in colour, but in this case the ultimate effect is not a
fading but a discoloration of white to a more or less distinct yellow
or brown colour, due to changes in the fibre which may often be traced
to excessive bleaching. In this case the fading of colour is directly
due to deterioration of the paper itself, and may occur in celluloses
of the best type. With lower-grade papers containing mechanical wood
pulp the degradation of colour and fibre is inevitable.

_Air and Moisture._--The exact effects produced on paper freely
exposed, or in books as ordinarily stored, depend upon the condition of
the atmosphere. Pure air has little or no action upon paper, cellulose
being a remarkably inert substance, and even in impure mechanical wood
pulp, if merely exposed to pure dry air, the signs of decay would be
delayed considerably. The combined action of air and moisture is of a
more vigorous character in promoting oxidation changes in the fibres,
or a dissociation of the sizing and other chemical ingredients of the
paper. The presence of moisture is, indeed, absolutely essential for
the reaction of some substances upon one another, and it is easy to
show that certain chemical compounds can be left in ultimate contact,
if absolutely dry, for a lengthened period without reacting, but the
addition of a little moisture at once produces chemical union. This may
be shown by a simple experiment.

Thus a piece of coloured paper which may be bleached immediately
if suspended in an atmosphere of ordinary chlorine gas will remain
unbleached for several hours if first thoroughly dried in an oven and
exposed to dry gas.

In the case of books and papers, these conditions which promote slow
disintegration are aggravated by the presence of impurities in the
air, such as the vapours of burning gas, the traces of acidity in
the atmosphere of large manufacturing towns, the excessive dampness
and perhaps heat of a climate favouring the growth of organisms. All
these factors are of varying degrees in different places, so that the
deterioration of papers does not proceed in the same measure and at the
same rate everywhere.

_Moisture._--It may not be out of place to discuss some important
relations between moisture and the physical qualities of a sheet of
paper. A paper in its normal condition always contains a certain
proportion of water as one of its ingredients, and the presence of this
moisture has much to do with the strength, elasticity, and use of the
paper, the absence of moisture giving rise to defects and troubles in
the use of the paper which to a certain extent lower its commercial
value and deteriorate it, though not perhaps in the sense of permanent
degradation of quality.

One trouble frequently experienced by stationers and others is that
known as wavy edges. The edges of a stack containing sheets of paper
piled upon one another frequently twist and curl, producing what are
known as wavy edges. This arises from the fact that the paper when
manufactured was deficient in natural moisture, and that when stacked
it has gradually absorbed moisture, which is taken up first by the
edges exposed to the air. This causes unequal expansion of the fibres
with the production of the so-called wavy edges. The only remedy in
such cases is the free exposure of the sheets before printing, so that
the moisture is absorbed equally all over the sheet. The cracked edges
of envelopes may be explained by reference to the same conditions. The
paper is worked up into envelopes in an over-dry condition, and the
fibres, being somewhat brittle, readily break apart from one another.
If the paper is kept in stock for some time before use this defect can
be very largely remedied.

With supercalendered papers it is only possible to obtain the best
results by allowing the paper to stand for several days after making
before it is glazed.

It is evident from these few examples that many of the troubles
experienced by printers are due to the fact that orders for paper
are frequently accompanied by an instruction for immediate delivery,
under which circumstances it is impossible to obtain the best results.
The expansion of papers used for lithography, and the bad register
frequently seen in colour work, may be explained by reference to the
behaviour of the individual fibres towards moisture. The expansion is
usually greater in one direction of the paper than in the direction
at right angles to it, and this is due to the fact that fibres have a
greater ratio of expansion in the diameter than in the length.

The behaviour of papers when damped is a peculiarity well known to
paper-makers and printers. For certain purposes it is desirable that
paper should not show any material alteration when damped, since
any expansion of the sheet is liable to throw the printing out of
"register." The liability of papers to such stretch or expansion is
largely minimised by careful manipulation of the pulp during the
process of beating, and also by a proper regulation of the web of paper
as it passes from the wet end of the paper machine over the drying
cylinders to the calenders. The paper which fulfils the necessary
qualifications as to a minimum stretch is prepared from pulp which has
not been beaten for too long a period, so that the pulp obtained is
fairly light and bulky. By this means the expansion of the fibres takes
place in the sheet itself without making any material alteration in its
size. That is to say, as the sheet of paper is fairly _open_, there is
sufficient room for expansion, which thus takes place with the least
alteration of the total area of the sheet. The paper which is allowed
to shrink on the machine during the process of drying, without undue
tension, usually exhibits a minimum amount of expansion subsequently in
printing.

It is important to notice that the expansion of paper is different for
the two directions, that is for the machine and cross directions.

This arises from the fact that in the machine-made paper the greater
proportion of the fibres point in the direction of the machine while
the paper is being made. In consequence of this the expansion of the
paper is greatest in what is known as the cross direction of the paper,
that is, in the direction at right angles to the flow of the pulp along
the machine wire.

This is to be explained by reference to the behaviour of fibres when
damped or brought into contact with an excess of water. The question
of the exact changes in the dimensions of a fibre due to absorption of
water has been dealt with in an interesting manner by Hohnel. He points
out that the well-known peculiarity of the shrinkage of ropes which
have been lying in the water can be explained by an examination of the
behaviour of the single fibres. He relates in detail the experiment
which can be carried out for the exact observation of the fibres when
in contact with water. A dry fibre when soaked in water appears to
become 20 to 30 per cent. greater in diameter, whereas in length it is
usually only increased by one-tenth per cent.

The method adopted by Hohnel was to place a fibre of convenient length
on a glass slip down the centre of which was a fine narrow groove
capable of holding water, so that the fibre could be wetted. Over the
fibre was a cover glass with a small scale marked on it. The loose
end of the fibres passed over a small roller and was stretched by a
light weight. The movements of the fibre were measured by means of an
eye-piece micrometer.

In this way it is possible to determine alterations in length to within
0·005 per cent., and this variation can be directly seen under the
microscope.

Hohnel observes in his account of the experiments that all fibres
become thicker when wetted, that vegetable fibres are more susceptible
than animal fibres.

Animal fibres expand about 10 to 14 per cent. in diameter, but
vegetable fibres as much as 20 per cent., as shown in the following
table:--

  -------------+----------+------------------+----------
  Animal Fibre.| Per Cent.| Vegetable Fibre. | Per Cent.
  -------------+----------+------------------+----------
  Human hair   |  10·67   | New Zealand flax |   20·0
  Angora wool  |  10·2    | Aloe hemp        |   25·8
  Alpaca wool  |  13·7    | Hemp             |   22·7
  Tussah silk  |  11·0    | Cotton           |   27·5
  -------------+----------+------------------+----------

The reverse is the case when the expansion of the fibres in regard to
length is considered, since animal fibres expand 0·50 to 1·00 per cent.
of their length, and vegetable fibres only 0·05 to 0·10 per cent.

The maximum amount of expansion in the case of the vegetable fibres is
obtained by gently breathing upon them rather than by the use of an
excess of water.

These figures are important as explaining many of the peculiar
characteristics of vegetable and animal fibres. Advantage is taken of
the greater expansion of the latter in the manufacture of instruments
for the measurement of moisture, such as the hair hygrometer, in which
the elongation of a stretched hair registers the variation in the
moisture of the atmosphere.

_Quality of Book Papers._--The Committee of the Society of Arts in
dealing with the evidence as to the permanence of finished papers
suggest the following classification as indicating the desired
standards of quality:--


(A) CLASSIFICATION AS TO FIBRES.

  A. Cotton, flax, and hemp.

  B. Wood celluloses, (_a_) sulphite process, and (_b_) soda and
      sulphate process.

  C. Esparto and straw celluloses.

  D. Mechanical wood pulp.

The Committee find little fault with the Principles which govern the
trade in the manufacture of high-class papers, and limit the result of
their investigation to the suggestion of a normal standard of quality
for book papers required in documents of importance according to the
following schedule:--

  _Fibres._--Not less than 70 per cent. of fibres of Class A.

  _Sizing._--Not more than 2 per cent. rosin, and finished with the
            normal acidity of pure alum.

  _Loading._--Not more than 10 per cent. total mineral matter (ash).

With regard to written documents, it must be evident that the proper
materials are those of Class A, and that the paper should be pure,
sized with gelatine and not with rosin. All imitations of high-class
writing papers, which are in fact merely disguised printing papers,
should be carefully avoided.

These recommendations are good as far as they go, but in order to
establish the proper standards of quality some specifications must be
laid down with regard to the strength of the paper and its physical
properties, together with a reference to the use for which the paper
is intended. The physical condition of the paper itself apart from the
nature of the fibre has much to do with its resistance to wear and
tear, and this is easily proved by comparing modern book papers made
from esparto with book papers of an earlier date made from the same
material.

The only official schedule of requirements in relation to public
documents is that issued by the Stationery Office.

The details set out relate chiefly to questions of weight and strength,
the limits being expressed in definite form and not allowing much
margin for variation in respect of strength or fibrous constituents.
Mechanical wood pulp is excluded in all papers except common material
as stated in the schedule. The papers required for stock are divided
into twelve classes. In each class the trade names of various sized
papers are given, the size of the sheet and the weight of the ream,
and, where required, any special characteristics are set out. The
schedule is as follows:--


_Class 1. Hand-made or Mould-made._

_General Specification._--Hand-made or mould-made. Animal tub-sized.
("Hand-made" or "Mould-made" to be marked on the wrapper.)

Where special water-marking is required mould will be supplied by the
Stationery Office for those papers made by hand.


_Class 2. Writings, Air-dried._

_General Specification._--Plate rolled. Machine made. Animal tub-sized.
Air-dried. (Must bear ink after erasure.)

_Note._--The mean breaking strain and mean stretch required are given
for each paper. The figures represent the mean of the results obtained
for both directions of the sheet, and are calculated on a strip of
paper five-eighths of an inch wide and having a free length of seven
inches between the clips.


_Class 3. Writings, Ordinary._

_General Specification._--Rolled. Machine-made. Animal tub-sized.


_Class 4. Writings, Coloured._

_Specification._--Highly rolled. Machine-made. Animal tub-sized.


_Class 5. Blotting Papers._

_Specification._--All rag. Machine-made. Free from loading.


_Class 6. Printing and Lithographic Papers._

_General Specification._--Rolled. Machine-made. Engine-sized. Loading
not to exceed 15 per cent.


_Class 7. Coloured Printings._

_General Specification._--Rolled. Machine-made. Engine-sized.


_Class 8. Copying and Tissue Papers._

_Specification._--Machine-made. Free from loading. (Copying papers are
required to give three good copies.)


_Class 9. Brown Papers, Air-dried._

_Specification._--Air-dried. Machine-made.

_Note._--The mean breaking strain and mean stretch required are given
for each paper. The figures represent the mean of the results obtained
for both directions of the sheet, and are calculated on a strip of
paper two inches wide and having a free length of seven inches between
the clips.

In the case of papers indicating a larger breaking strain than the
minimum required, a proportional increase in the stretch must also be
shown.


_Class 10. Brown Paper, Cylinder-dried._

_General Specification._--Machine-made.

_Note._--The mean breaking strain required is given for each paper. The
figures represent the mean of the results obtained for both directions
of the sheet, and are calculated on a strip of paper two inches wide
and having a free length of seven inches between the clips.


_Class 11. Smallhands._

_General Specification._--Machine-made. Engine-sized.


_Class 12. Buff Papers._

_Specification._--Highly finished both sides. Machine-made. Hard
engine-sized.

Mechanical wood pulp must not be used in the manufacture of any papers,
with the exception of engine-sized coloured printings, and buff papers,
where an addition up to 25 per cent. will be allowed.

All animal tub-sized papers are required to be as far as possible free
from earthy matter; and, except where specially stated, the amount of
_loading_ added to other papers must not exceed 6 per cent.

When sulphite or soda pulps are used, either separately or conjointly,
in the manufacture of printing papers, the quantity of neither material
shall separately exceed 50 per cent.

The most complete specification as to the requirements for standard
papers is that published by the Paper Testing Institute in Germany, and
used as the basis of most contracts, at least for public and official
documents.

_Standards of Quality in Germany._--The classification of papers
according to the raw materials used and the nature of the finished
paper is very complete. The classification is made under three
headings: (_A_) Raw Material; (_B_) Strength; (_C_) Uses.


_(A) Classification according to Material._

(1) Paper made from rags only (linen, hemp, and cotton).

(2) Paper made from rags with a maximum of 25 per cent. of cellulose
from wood, straw, esparto, manila, etc., but free from mechanical wood
pulp.

(3) Paper made from any fibrous material, but free from mechanical wood
pulp.

(4) Paper of any fibrous material.


_(B) Classification according to Strength._

  ----------------------+-------+-------+-------+-------+-------+------
          Class         |   1.  |   2.  |   3.  |   4.  |   5.  |   6.
  ----------------------+-------+-------+-------+-------+-------+------
  Mean tearing length   |       |       |       |       |       |
   in metres            | 6,000 | 5,000 | 4,000 | 3,000 | 2,000 | 1,000
                        |       |       |       |       |       |
  Elasticity per cent.  |   4   |  3·5  |   3   |  2·5  |   2   |  1·5
                        |       |       |       |       |       |
  Resistance to folding |       |       |       |       |       |
   (Schoppers' method,  |       |       |       |       |       |
   number of foldings)  |  190  |  190  |   80  |   40  |   20  |   3
  ----------------------+-------+-------+-------+-------+-------+------

The tests for tearing length, resistance to folding, elasticity,
etc., are made in air showing relative humidity of 65 per cent. The
calculations for tearing length are made on strips of paper dried at
100° C.


_(C) Classification according to Use._

  ------+-------------------+------+----------+-----------+---------------
        |                   |      |          |           |   Weight of
        |                   |Fibre.| Strength.|  Size of  +-------+-------
  Class.|      Uses.        |Class.|  Class.  |  Sheets.  | 1,000 | 1 Sq.
        |                   |      |          |    Cm.    |Sheets.| Metre.
        |                   |      |          |           |  Kg.  | Grms.
  --+---+-------------------+------+----------+-----------+-------+-------
  1 | Writing papers for    |      |          |           |       |
    |  important documents  |  1   |    1     | 33   × 42 |  15   |  --
    |                       |      |          |           |       |
    | Paper for State       |      |          |           |       |
    |  documents            |  1   |    1     | 26·5 × 42 |  12   |  --
    |                       |      |          |           |       |
  2 | Paper for registers,  |      |          |           |       |
    |  account books,       |      |          |           |       |
    |  and ledgers--        |      |          |           |       |
    |                       |      |          |           |       |
    | (_a_) First quality   |  1   |    2     | 33   × 42 |  14   |  --
    |                       |      |          |           |       |
    | (_b_) Second quality  |  1   |    3     | 33   × 42 |  13   |  --
    |                       |      |          |           |       |
  3 | Documents intended to |      |          |           |       |
    |  be preserved longer |       |          |           |       |
    |  than ten years--     |      |          |           |       |
    |                       |      |          |           |       |
    | (_a_) Foolscap paper  |  2   |    3     | 33   × 42 |  13   |  --
    |                       |      |          |           |       |
    |       Letter paper    |      |          |           |       |
    |        (quarto size)  |  2   |    3     | 26·5 × 42 |  10·4 |  --
    |                       |      |          |           |       |
    |       Letter paper    |      |          |           |       |
    |        (octavo size)  |  2   |    3     | 26·5 × 21 |  5·2  |  --
    |                       |      |          |           |       |
    |       Duplicating     |      |          |           |       |
    |        paper          |  2   |    3     | 33   × 42 |  7    |  --
    |                       |      |          |           |       |
    | (_b_) Official        |      |          |           |       |
    |        writing paper  |  2   |    4     | 33   × 42 | 13    |  --
    |                       |      |          |           |       |
  4 | Paper for documents of|      |          |           |       |
    |  lesser importance--  |      |          |           |       |
    |                       |      |          |           |       |
    | (_a_) Foolscap paper  |  3   |    --    | 33   × 42 | 12    |  --
    |                       |      |          |           |       |
    |       Letter paper    |      |          |           |       |
    |        (quarto size)  |  3   |    --    | 26·5 × 42 |  9·6  |  --
    |                       |      |          |           |       |
    |       Letter paper    |      |          |           |       |
    |        (octavo size)  |  3   |    --    | 26·5 × 21 |  4·8  |  --
    |                       |      |          |           |       |
    | (_b_) Official        |      |          |           |       |
    |        writing paper  |  3   |    4     | 33   × 42 | 12    |  --
    |                       |      |          |           |       |
  5 | Envelopes and         |      |          |           |       |
    |  wrappers--           |      |          |           |       |
    |                       |      |          |           |       |
    | (_a_) First quality   |  --  |    3     |    --     |  --   |  --
    |                       |      |          |           |       |
    | (_b_) Second quality  |  --  |    5     |    --     |  --   |  --
    |                       |      |          |           |       |
  6 | Writing paper of      |      |          |           |       |
    |  medium quality       |  --  |   5-6    |    --     |  --   |  --
    |                       |      |          |           |       |
  7 | Covers for documents--|      |          |           |       |
    |                       |      |          |           |       |
    | (_a_) That required   |      |          |           |       |
    |       for frequent use|  1   | Tearing  | 36   × 47 | 81·2  |  480
    |                       |      |  length  |           |       |
    |                       |      |  2,500   |           |       |
    |                       |      |Elasticity|           |       |
    |                       |      |   3·5%   |           |       |
    |                       |      |          |           |       |
    | (_b_) For other       |      |          |           |       |
    |        purposes       |  3   | Tearing  | 36   × 47 | 42·3  |  250
    |                       |      |  length  |           |       |
    |                       |      |  2,500   |           |       |
    |                       |      |Elasticity|           |       |
    |                       |      |   2·5%   |           |       |
    |                       |      |          |           |       |
  8 | Printing paper--      |      |          |           |       |
    |                       |      |          |           |       |
    | (_a_) For important   |      |          |           |       |
    |        printed matter |  1   |    4     |    --     |  --   |  --
    |                       |      |          |           |       |
    | (_b_) For less        |      |          |           |       |
    |        important      |      |          |           |       |
    |        printed matter |  3   |    4     |    --     |  --   |  --
    |                       |      |          |           |       |
    | (_c_) For common use  |  --  |   5-6    |    --     |  --   |  --
  --+-----------------------+------+----------+-----------+-------+-------




CHAPTER XIII

BIBLIOGRAPHY

ANALYSIS, TECHNOLOGY, ETC.


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russischen Papierfabriken. _Petersburg_, 1906.

MÜLLER, L.--Die Fabrikation d. Papiers in Sonderheit d. a. d. Maschine
gefertigten. 2 Aufl. 1855.

MÜLLER UND A. HAUSSNER.--Die Herstellung u. Prüfung des Papiers. 1905.

MÜLLER, A.--Qualitative und quantitative Bestimmung des Holzschliffes
im Papier. 1887.

MUTH. Die Leimung der Papierfaser im Holländer und die Anfertigung
fester Papiere. 1890.

NAYLOR, W.--Trades Waste. _London_, 1902.

NORMALPAPIER.--Sammlung der Vorschriften für amtliche Papier- und
Tintenprüfung. _Berlin_, 1892.

PIETTE, L.--Traité de la coloration des pâtes à papier. Précédé d'un
aperçu sur l'état actuel de la fabrication du papier. Avec échantillons
de papiers colorés. _Paris_, 8^o, 1863.

REJTÖ, A.--Anleitung für Private zur Durchführung der Papierprüfung.
_Budapest_, 1893.

ROSSEL.--Papiere und Papierprüfung mit Berücksichtigung der in der
Schweiz verwendeten Schreib- und Druckpapiere. _Biel_, 1895.

SCHUMANN, DR. G.--Welche Ursachen bedingen die Papierqualität.
_Biberach_, 1901.

SINDALL, R. W.--Paper Technology. _London_, 1906.

STEVENS, H. P.--The Paper Mill Chemist. _London_, 1907.

WIESNER, J.--Mikroskopische Untersuchung des Papiers mit besonderer
Berücksichtigung der ältesten orientalischen und europäischen Papiere.
_Wien_, 1887.

WIESNER, J.--Mikroskopische Untersuchung alter ostturkestanischer
und anderer asiatischer Papiere nebst histologischen Beiträgen zur
mikroskopischen Papieruntersuchung. _Wien_, 1902.

WINKLER, O.--Die Trockengehalts-Bestimmung d. Papierstoffe. 1902.

WINKLER, O., UND KARSTENS, H.--Papieruntersuchung. 1903.

WURSTER.--Le collage et la nature du papier. _Paris_, 1901.

WURSTER, DR. C.--Die neuen Reagentien auf Holzschliff und verholzte
Pflanzenteile zur Bestimmung des Holzschliffs im Papier. _Berlin_.

ZIRM, A.--Der Papierfärber. _Tilsit_, 1904.


CELLULOSE, ETC.

BEADLE, C.--Viscose and Viscoid. Franklin Institute reprint. 1896.

BERSCH, J.--Cellulose, Celluloseprodukte u. Kautschuksurrogate. 1903.

BOCKMANN, F.--Das Celluloid, sein Rohmaterial, Fabrikation,
Eigenschaften u. technische Verwendung. 1880. 2te Aufl. 1894.

BORNEMANN, GR.--Ueber Cellulose and neuere Umwandlungsprodukte
derselben. _Biberach_, 1901.

BOTTLER, M.--Die vegetabilischen Faserstoffe--Hartleben's
chemisch-technische Bibliothek. 1900.

BUTSCHLI, O.--Untersuchgn. an Gerinnungsschaumen, Sphärokystallen u. d.
Struktur v. Cellulose. 1894.

CROSS, C. F., AND BEVAN, E. J.--Cellulose. _London_, 1885.

    2nd edition. 1895.

CROSS AND BEVAN.--Researches on Cellulose. 1895-1900.

    Ditto, 1900-1905.

MARGOSCHES, DR. B.--Die Viskose, ihre Herstellung, Eigenschaften und
Anwendung. _Leipzig_, 1906.

SCHLESINGER.--Künstliche Seide (Zellstoff-Seide).
Mechanisch-technologische Untersuchung der aus nitriertem Zellstoffs
hergestellten Seide. 1895.


FIBRES, ETC.

ANDÉS, L. E.--Die Verarbeitung des Strohes. _Wien_, 1898.

BAGSHAW.--Photomicrography. Elementary.

BENGAL GOVERNMENT.--Jute in Bengal, and on Indian Fibres available for
the Manufacture of Paper. Report by H. Kerr. _Calcutta_, fol., 1874.

BLEEKRODE, S.--Grondstoffen voor Papierbereiding, bijzonder in
Neerlandsch-Indië (excerpt). 8^o, 1859.

BOTTLER, M.--Die animalischen Faserstoffe. 1901.

CARTER.--Spinning of Fibres. 1904.

COBBETT.--A Treatise on Cobbett's Corn. 1828. (Printed on paper made of
corn husks.)

CHRISTY.--Commercial Plants and Drugs. 1882.

CROSS AND BEVAN.--Report on Indian Fibres. 1887.

CROSS, C. F.--Report on Miscellaneous Fibres. 1886.

CROSS, C. F.--Bast Fibres. _Manchester_, 1880.

DALEN, G.--Jute. Manila, Adansonia. 1902.

DÉPIERRE, J.--Traité des apprêts et spécialement des tissus de coton,
blancs, teints et imprimés.

DODGE, C. R.--Leaf Fibres of the United States. 1903.

GARÇON, JULES.--Bibliographie de la technologie chimique des fibres
textiles. _Paris_, 1893.

GELDER ZONEN, VAN.--Een woord over nieuwe Grondstoffen voor Papier, met
monsters van ded proeven, etc. _Amsterdam_, sm. 4^o, 1866.

GEORGIEVICS, G. V.--Lehrbuch der chemischen Technologie der
Gespinnstfasern. 1895-98.

GEORGIEVICS, G. V.--Lehrbuch d. chemischen Technologie d.
Gespinnstfasern. 2te Tle. 1898-1902.

GEORGIEVICS, G. V.--Technology of Textile Fibres; from the German. 1902.

GROTHE, H.--Die Technologie der Gespinnstfasern. 1876-82.

GOODALE.--Physiological Botany. 1890.

HAMMARSTEN, O.--Untersuchungen über d. Faserstoffgewinnung, 1875.

HANNAN, W. I.--Textile Fibres of Commerce. 1902.

HOYER, E. VON.--Die Verarbeitung der Faserstoffe. (Spinnerei,
Papierfabrikation.) 3te Aufl. 1900.

JOHNSTONE.--Esparto. (Society of Arts Lecture.) 1870.

KEW BULLETIN.--Vegetable Fibres. 1901.

LECOMTE, H.--Les textiles végétaux; leur examen microchimique. _Paris_,
1891.

LIOTARD.--Materials in India suitable for Paper-making. _Calcutta_,
1880.

MORRIS, DR.--Commercial Fibres. (Cantor Lectures.) 1895.

MÜLLER, HUGO.--Pflanzenfaser. _Leipzig_, 1873.

PAYEN, A.--Succédanés des chiffons. Paris Universal Exhibition.
Rapports du Jury International, Classe 7, sect. ii. 8^o, 1867.

PFUHL, E.--Papierstoffgarne, ihre Herstellung, Eigenschaften u.
Verwendbarkeit. 1904.

POSSELT, E. A.--The Structure of Fibres, Yarns, and Fabrics, being
a Practical Treatise for the use of all persons employed in the
Manufacture of Textile Fibres. 2 vols., 1902.

ROSTAING AND OTHERS.--Précis historique, descriptif, analytique et
photomicrographique, des végétaux propres à la fabrication de la
cellulose et du papier. _Paris_, 8^o, 1900.

ROUTLEDGE, T.--Bamboo considered as a Paper-making Material, with
Remarks upon its Cultivation and Treatment. _London_, 8^o, 1875.

ROUTLEDGE, T.--Bamboo and its Treatment. 1879.

SILBERMANN, H.--Fortschritte auf dem Gebiete der chemischen Technologie
d. Gespinnstfasern, 1885-1900. 2te Tle., 1902-03.

TRABUT.--Étude sur l'alfa. 1889.

URBAIN, V.--Les succédanés du chiffon en papeterie. _Paris_, 16^o, 1897.

VÉTILLART.--Études sur les Fibres Végétales. _Paris_, 1876.

WIECK, F. G.--Bilder aus Gewerbskunst (aus Tomlinson's "Objects in Art
Manufacture"), i. Papier. _Leipzig_, sm. 8^o, 1855.

WITT, O. N.--Chemische Technologie der Gespinnstfasern, ihre
Geschichte, Gewinnung, Verarbeitg. u. Veredlung. 1888-1902.

ZETZSCHE.--Die Wichtigsten Faserstoffe der europäischen Industrie.
Anleitung zur Erkennung und Unterscheidung. 1905.

ZIMMERMANN, A.--Morphologie und Physiologie der Pflanzenzelle.


HISTORICAL.

BLANCHET, AUGUSTIN.--Essai sur l'histoire du papier et de sa
fabrication. _Paris_, 1900.

BREITKOFF, J. G. J.--Ursprung der Spielkarten, die Einführung des
Leinenpapieres, etc., in Europa. (Completed by J. G. F. Roch.)
_Leipzig_, 2 vols., 4^o, 1784-1801.

BRIQUET, C. M.--Bemerkungen über das Sammeln von Wasserzeichen
oder Papiermarken, überreicht bei der Ausstellung der alten
Papiermarkerkunst zu Paris. 1900.

BRIQUET, C. M.--Papiers et filigranes des archives de Gênes 1154-1700.
_Geneva_, 1888.

BRIQUET, C. M.--Geschichte der Papierzeichen von ihrem Erscheinen gegen
1282 bis 1600. Mit Beigabe von 15500. 1906.

BUTLER PAPER CO.--The Story of Paper-making. _Chicago_, sm. 8^o, 1901.

COLLETT, C. D.--History of Taxes on Knowledge. _London_, 1899.

CONGRESS.--International congress de fabricants de papier et carton,
Antwerp. Comptes rendu des séances. _Bruxelles_, 8^o, 1894.

DROPISCH, B.--Die Papiermaschine, ihre geschichtliche Entwicklung u.
Construction. 1878.

EGGER, E.--Le papier dans l'antiquité et dans les temps modernes.
_Paris_, 16^o, 1866.

EVANS, L.--The Firm of John Dickinson & Co., with an Appendix on
Ancient Paper-making. _London_, sm. 8^o, 1896.

GAMBLE, J.--Collection of Documents (Specifications, Official Reports,
etc.) respecting the Claims of L. Robert as the Original Inventor, and
of J. Gamble as the First Introducer of the French Paper-machine. Fol.,
1801--58.

HOERNLE, A. F.--Who was the Inventor of Rag Paper? 1903.

HÖSSLE, F. VON.--Geschichte der alten Papiermühlen in ehemaligen Stift
Kempten und in der Reichsstadt Kempten. 1901, 4^o, 1900.

HUNTER, J.--Specimen of Marks used by Early Manufacturers of Paper
(Excerpt). _London_, 4^o, 1858.

IMBERDIS, J.--Le papier ou l'art de fabriquer de papier. Traduction
au Français de (papyrus sive ars conficiendæ papyri, 1693), par A.
Blanchet. Avec le texte latin. 1899.

JACKSON, J. B.--An Essay on the Invention of Engraving and Printing in
Chiaro Oscuro, as practised by Durer, etc., and its Application to the
Making of Paperhangings. _London_, sm. 4^o, 1754.

JANSEN, H.--Essai sur l'origine de la gravure, etc. _Paris_, 2 vols.,
8^o, 1808.

JENKINS, R.--Paper-making in England, 1495, etc., from the _Library
Association Record_, September, 1900-April, 1902. _London_, 8^o.

KARABACEK, J.--Das arabische Papier. _Wien_, 1887.

KENT & CO.--Paper and Paper-making Chronology. _London_, 8^o, 1875.

KIRCHNER, E.--Die Papiere des XIV. Jahrhunderts im Stadtarchive zu
Frankfurt a. M. 1893.

KIRCHNER, E.--Das Papier. Die Geschichte d. Papierindustrie; die
Rohstofflehre d. Papierindustrie. 3 Bde., 1897-99.

KIRCHNER, E.--Das Papier. Historisch-technologische Skizzen.
Jahresbericht der Techn. Lehranstalten in Chemnitz. 1903.

KLEIN, A.--Entwicklung und Aufgaben der Papierindustrie. _Biberach_,
1906.

KLEMM, P.--Papier-warenzeichen ... vom 1 Okt., 1894, bis Ende 1902, für
Klasse 27, umfassend Papier, etc., eingetragenen Wort- und Bildzeichen.
_Leipzig_, sm. 8^o, 1903.

KOOPS, M.--Historical Account of Paper, and of Substances used prior to
its Invention (printed on paper made from straw and wood). _London_,
8^o, 1800.

    Ditto, 2nd edition, 1801.

LACROIX, A.--Historique de la papeterie d'Angoulême suivi
d'observations sur le commerce de chiffons en France. _Paris_, 8^o,
1863.

LALANDE, J. J. LE F. DE.--L'art de faire le papier. Acad. Roy. des
sciences. Description des Arts et Métiers, vol. 1. Fol., 1761.

LETTRE sur les découvertes de M. Didot aîné dans les arts de ... la
papeterie (l'invention du papier-vélin). _Paris_, 12^o, 1783.

LEUCHS, J. C.--Beschreibung der in den letzten acht Jahren in der
Papierfabrikation gemachten Verbesserungen. Nachtrag. _Nürnberg_, 8^o,
1828.

MARABINI.--Bayrische Papiergeschichte. 1 Teil. Die Papiermühlen im
Gebiete der weiland freien Reichsstadt Nürnberg. _Nürnberg_, 1894.

MAUREL, F.--Le papier japonais. Histoire et fabrication d'après les
documents Anglais et indigènes (excerpt). _Paris_, 4^o, 1871.

MEERMAN, G., AND OTHERS.--Epistolæ, etc., de chartæ vulgaris lineæ
origine. Ed. J. Van Vassen, Hagæ Com. Sm. 8^o, 1767.

MIDOUX, E., AND MATTON, A.--Étude sur les filigranes des papiers
employés en France aux 14^e et 15^e siècles. _Paris_, 8^o, 1868.

MILLAR, O.--Papier-Industrie. Schweizerische Landesausstellung, 1883.
Berichte, Gruppe 8, 1884.

MURRAY, J.--Practical Remarks on Modern Paper, etc., with an
Introductory Account of its Former Substitute. _Edinburgh_, 8^o, 1829.

PARLATORE, P.--Mémoire sur le papyrus des Anciens et sur le papyrus
de Sicile, Acad. des Sciences. Paris. Mèm. par divers Savans.... 2^e
Serie, Tome 12. 4^o, 1854.

PEIGNOT, E. G.--Essai sur l'histoire du parchemin et du vélin. _Paris_,
8^o, 1812.

PENIG.--(Patentpapierfabrik zu Penig.) Ein Beitrag z. Geschichte d.
Papiers, 1897.

ROBERT, N. L.--Le centenaire de la machine a papier continu. Son
invention par N. L. Robert en 1799. Biographie de l'inventeur, par
J. Breville. Historique des divers perfectionnements ... par Didot
Saint-Leger, 1800-1818. _Paris_, 8^o, 1901.

ROBERTSON.--Fifty Years' Experience in Paper-making. _Leith._

SCHAEFFER, J. C.--Proefnemingen en Monster-Bladen om Papier te maaken
zonder Lumpen of met een gering Byvoegzel derzelven. Uit het Hoogduits
vertaald. Deel 1-2. _Amsterdam_, 2 vols., sm. 4^o, 1770.

SCHAEFFER, J. C.--Sämtliche Papierversuche, 2te Aufl. Nebst 81 Mustern
und 13 Kupfertafeln. _Regensburg_, 6 vols. in one, sm. 4^o, 1772.

SCHAEFFER, J. C.--Erweis in Musterbogen dass die neuen Papierarten
... sich allerdings auch zu Tapeten übermahlen und gebrauchen lassen.
_Regensburg_, fol.

SMITH, J. E. A.--History of Paper, Genesis and Revelations. _Holyoke,
Mass., U.S.A._, 1882.

SOTHEBY, S. L.--The Typography of the 15th Century ... Exemplified
in a Collection of Facsimiles from 100 Works, with their Watermarks.
_London_, fol. 1845.

SOTHEBY, S. L.--Principia Typographica. An Attempt to Elucidate the
Paper Marks of the Period. _London_, 3 vols., fol. 1858.

SPECHTHAUSEN.--Hundert Jahre der Papierfabrik Spechthausen.
Festschrift, z. 1887.

SPICER, A.--The Paper Trade. _London_, 1907.

STOPPELAAR, J. H. DE.--Het Papier in de Nederlanden gedurende de
middeleeuwen, inzonderheid in Zeeland. _Middelburg_, 8^o, 1869.

TOMLINSON, C.--Illustrations of the Useful Arts. No. 3, Paper.
_London_, 32^o, 1859.

VILLETTE, C. MARQUIS DE.--[OE]uvres, with Specimens of Paper. _Londres_,
16^o, 1786.

WILLKOMM, M.--Über den Lotos und Papyros der alten Ägypter und die
Papiererzeugung in Altertume. _Prag_, 1892.


PAPER MANUFACTURE.

ARCHER, T. C.--The Manufacture of Paper. Bevan. British Manufacturing
Industries, viii. Sm. 8^o, 1876.

ARNOT.--Technology of the Paper Trade (Cantor Lecture, Society of
Arts). _London_, 1877.

BARSE, J.--Études comparées sur l'industrie Française, ii. La
fabrication et le commerce du papier en 1860 et en 1864. _Paris_, l.
8^o, 1864.

BEADLE, C.--Paper Manufacture--Lectures. 1901.

BEADLE, C.--Chapters on Paper-making. Vol. 1. _London_, 1904.

    Vol. 2, Answers to Technological Questions. 1906.

    Vol. 3, Practical Points in Paper Manufacture. 1907.

    Vol. 4, Ditto. 1907.

BEAUMONT, F.--Report on Apparatus and Processes used in Paper-making,
etc. Paris Universal Exhibition, 1867. British Commercial Reports, Vol.
4. 8^o, 1867.

BENNETT, J. B.--Paper-making Processes and Machinery, with
Illustrations of Paper-making Machinery constructed by Bertrams, Ltd.
_Edinburgh_, 8^o, 1892.

BERTRAMS, LTD.--Specimens of Paper. _Edinburgh_, obl. 16^o, 1892.

BLANCHET, A.--Fabrication du papier. Rapports, Paris Universal
Exhibition, 1900.

BROWN, H. T.--The Manufacture of Paper from Wood in the United States.
1886.

BUROT.--Note sur la fabrication du papier de paille. _Paris_, 8^o, 1883.

CAMPREDON, E.--Le Papier. Étude monographique sur la papeterie
Française et en particulier sur la papeterie Charentaise. i.
Historical; ii. Descriptive of Modern Paper-making; iii. Co-operative
Paper-making. _Paris_, 8^o, 1901.

CHARPENTIER, P.--Le Papier. Fremy, E. Encycl. Chim., Tome X. 8^o (83),
1890.

CLAPPERTON, G.--Practical Paper-making. _London_, sm. 8^o, 1894.

    Ditto, 2nd edition, 1907.

CONEY, E.--Paper-making Machinery and Fibres. Philadelphia
International Exhibition, 1876. U.S.A. Centennial Commission Reports
and Awards, Group xiii. 8^o, 1876.

DALHEIM, C. F.--Taschenbuch f. d. prakt. Papierfabrikanten. 3te Aufl.
1896.

DAMMER, O.--Papierfabrikation.

DAVIS, C. T.--The Manufacture of Paper. _Philadelphia_, 8^o, 1886.

DOUMERC AND OTHERS.--Matériel et procédés de la papeterie, etc. Paris
Univ. Exhibition, 1867. Rapports du Jury International, Classe 59. 8^o,
1867.

DOYLE, P.--Paper-making in India, being Notes of a Visit to the Lucknow
Paper Mill. _Lucknow_, 8^o, 1885.

DROPISCH, B.--Handb. d. Papierfabrikation. 3e Aufl. 31 Taf. in fol.
1881.

DUNBAR, J.--The Practical Papermaker. _Leith_, 12^o, 1881.

HARTMANN, C.--Handb. d. Papierfabrikation. Taf. 1842.

HASSAK, K.--Die Erzeugung des Papieres.

HAUSNER, A.--Der Holländer. Eine kritische Betrachtung seiner
Arbeitsweise mit Bezug auf die Einzelabmessungen seiner Teile und die
verarbeiteten Fasern. 1901.

HERRING, R.--Paper and Paper-making, Ancient and Modern. _London_, 8^o,
1854.

    Ditto, 2nd edition, 1855.

    Ditto, 3rd edition, 1863.

HOFMANN, C.--A Practical Treatise on the Manufacture of Paper in All
its Branches. _Philadelphia_, 4^o, 1873.

HOFMANN, C.--Praktisches Handbuch d. Papierfabrikation. 1873.

HOFFMANN, TH.--Papierprägung. _Berlin._

HOYER, E.--Das Papier, seine Beschaffenheit und deren Prüfung.
_München_, 1882.

HOYER, E.--Über die Entstehung und Bedeutung der Papiernormalien, sowie
deren Einfluss auf die Fabrikation des Papieres. _München_, 1888.

HOYER, E.--Die Fabrikation des Papiers. 1900.

HOYER, E.--Die Fabrikation des Papiers, nebst Gewinnung d. Fasern. 1887.

HÜBNER, J.--Paper Manufacture (Cantor Lectures to the Society of Arts).
1903.

JAGENBERG, F.--Das Holländergeschirr. Remscheid. 1894.

KIRCHNER-STROHBACH.--Holländer-Theorie. Biberach. 1904.

KLEMM, DR. P.--Über Papier. Klimsch's Graphische Bibliothek Bd. 3
(Farbe und Papier im Druckgewerbe). 2 Teil. _Frankfurt a. M._ 1900.

KORSCHILGEN UND SELLEGER.--Technik und Praxis der Papierfabrikation.
_Berlin_, 1906.

KRAFT, M.--Grundriss der mechanischen Technologie. Abt. ii. Spinnerei,
Weberei, und Papierfabrikation. 2te Aufl. _Wiesbaden_, 8^o, 1895.

LENORMAND, L. S.--Manuel du fabricant de papier. _Paris_, 2 vols.,
18^o, 1833.

    Ditto, 2nd edition. 1834.

LENORMAND, L. S.--Nouveau manuel complet du ... fabricant de papiers
peints. Nouv. ed. par Vergnand. _Paris_, 18^o, 1854.

LENORMAND, L. S.--Handbuch der gesammten Papierfabrikation, 2te Aufl.,
von C. Hartmann. _Weimar_, 2 vols., 12^o, 1862.

MERZ.--Behandlung der Papiermaschine.

MEYNIER, H.--Papier und Papier-Fabrikate. Paris Univ. Exhibition, 1867.
Austrian Comm. Berichte. Heft 8. 8^o, 1867.

MIERZINSKI, ST.--Handbuch d. Papierfabrikation. 3 Bde. 1886.

MÜLLER, F. A. L.--Die Fabrikation des Papiers, in Sonderheit der auf
der Maschinen gefertigten, etc. 3te Aufl. _Berlin_, 8^o, 1862.

MÜLLER, DR. L.--Die Fabrikation des Papiers. _Berlin_, 1877.

OLMER, GEORGES.--Du papier mécanique.

ONFROY.--L'art du papier et le papier d'Arches. 1907.

PAPER-MAKING.--Paper-making, by the Editor of the Paper Mills
Directory, London. 2nd edition. 8^o, 1876.

PAPER-MAKER.--The Paper-makers' Handbook and Guide to Paper-making, by
a Practical Paper-maker. _London_, sm. 8^o, 1878.

PAPER-MANUFACTURE.--Essays by a Society of Gentlemen. No. vi., pp.
21-27. 1717.

PARKINSON, R.--Treatise on Paper, with Outline of Manufacture. 1886.

    Ditto, 2nd edition, 1896.

PAYEN, A., AND OTHERS.--La fabrication du papier et du carton. 3^e ed.
_Paris_, 8^o, 1881.

PAYEN, A., AND VIGREUX, L.--La papeterie. Études sur l'Exposition de
1867. Vol. 8. 8^o, 1867.

PFAU, F.--Der junge Papierhändler. _Berlin_, 1902.

PIETTE, L.--Manuel ... de papeterie et les succédanés (des chiffons).
_Paris_, 2 vols., 8^o, 1861.

PLANCHE, G.--De l'industrie de la papeterie. _Paris_, 8^o, 1853.

PLANCHE, G.--Der Papierfabrikation. Bearbeitet von C. Hartmann.
_Weimar_, 12^o, 1853.

PLANCHE, G.--Bericht über die Reinigung der Stoffe zur
Papierfabrikation. Uebersetzt und vervollständigt durch eine
chronologische Skizze der Papier-Erzeugung und der Verbesserungen an
den Maschinen zur Reinigung des Papier-Stoffs von A. Rudel. _Leipzig_,
8^o, 1862.

PROUTEAUX, A.--Practical Guide for the Manufacture of Paper and (Paper)
Boards. With a chapter on Wood Paper in the U.S. by H. T. Brown.
_Philadelphia_, 8^o, 1866.

PROUTEAUX, A.--Guide de la fabrication du papier et du carton. _Paris_,
12^o, 1864.

RAAB, R.--Die Schreibmaterialen und die gesamte Papierindustrie.
_Hamburg_, 1888.

REED, A. E.--Paper Manufacture. Society for the Promotion of Scientific
Industry. Artisans' Reports upon the Vienna Exhibition. 8^o, 1873.

RICHARDSON, W. H.--The Industrial Resources of the Tyne ... [Paper].
1864.

SCHUBERT, M.--Traité pratique de la fabrication de la cellulose. Trad.
p. E. Bibas. Toile. 1893.

SCHUBERT, M.--Die Praxis der Papierfabrikation mit besond.
Berücksichtigung der Stoffmischungen und deren Calculationen. 1897.

SCHUBERT, M.--Die Papierverarbeitung. 2 Bde. 1900-1901.

    Bd. I. Die Kartonnagen-Industrie.

    Bd. II. Die Buntpapierfabrikation.

SINDALL, R. W.--The Manufacture of Paper Pulp in Burma. Government
Press. _Rangoon_, 1907.

SINDALL, R. W.--The Manufacture of Paper. 1908. Constable & Co.
_London._

TWERDY, E.--Papier industrie. Berichte. _Wien_, 1873.

VACHON, M.--Les arts et les industries du papier. _France_, 1871-1894.

VALENTA, E.--Das Papier, seine Herstellung, Eigenschaften, Prüfung.
1904.

WANDERLEY, G.--Die Papierfabrikation und Papierfabrikanlage. _Leipzig_,
1876.

WATT, A.--The Art of Paper-making, with the Recovery of Soda from Waste
Liquors. _London_, sm. 8^o, 1890.

WEBER, R.--Papier-Industrie. Vienna Universal Exhibition, 1873.

WEHRS, G. F.--Vom Papier, den vor der Erfindung desselben üblich
gewesenen Schreibmassen und sonstigen Schreibmaterialien. _Halle_, 8^o,
1789.

WINKLER, O.--Der Papierkenner. 1887.


PAPER, SPECIAL KINDS.

ANDÉS, L. E.--Papier-Spezialitäten, praktische Anleitung zur
Herstellung. 1896.

ANDÉS, L. E.--Treatment of Paper for Special Purposes. Translated from
German. 1907.

ANDÉS, L. E.--Die Fabrikation der Papiermaché und Papierstoff-Waren.
_Leipzig_, 1900.

ANDÉS, L. E.--Blattmetalle, Bronzen und Metallpapiere, deren
Herstellung und Anwendung. _Wien_, sm. 8^o, 1902.

BOECK, J. P.--Die Marmorirkunst für Buchbindereien, Buntpapierfabriken.
_Wien_, sm. 8^o, 1880.

BRIQUET, M.--De quelques industries nouvelles dont le papier est la
base. _Genève_, 1885.

EXNER, W. F.--Tapeten- und Buntpapier-Industrie. Paris Univ.
Exhibition, 1867. Austrian Comm. Berichte. Heft 8. 1867.

EXNER, W. F.--Tapeten- und Buntpapier. Vienna Universal Exhibition,
1873. Officieller Ausstellungs-Bericht. Heft 53. 8^o, 1873.

FICHTENBERG.--Nouveau manuel complet du fabricant de papiers de
fantaisie, papiers marbrés, etc. _Paris_, 18^o, 1852.

HERRING, R.--Guide to Varieties and Value of Paper. 1860.

HOFMANN, A. W.--Report on Vegetable Parchment (Gaine's Patent, No. 2834
of 1853). _London_, 8^o, 1858.

KAEPPELIN, D.--Fabrication des papiers peints. Lacroix E., Études sur
l'exposition de 1867. Vol. 1. 8^o, 1867.

KAEPPELIN, D.--Fabrication des papiers peints. 1881.

LINDSEY, G.--Pens and Papiermaché. Bevan, G. P., Brit. Manufacturing
Industries (iii.). 12^o, 1876.

MORTON, G. H.--The History of Paper-hangings, with Review of other
Modes of Mural Decoration. _Liverpool_, 8^o, 1875.

SANBORN, K.--Old Time Wall Papers. 1905.

SCHMIDT, C. H.--Die Benutzung des Papiermaché. _Weimar_, 12^o, 1847.

SCHMIDT, C. H.--Die Papier-Tapetenfabrikation. 3te Aufl. _Weimar_,
12^o, 1856.

SCHMIDT, C. H.--The Book of Papiermaché and Japanning. _London_, 1850.

SEEMAN, TH.--Die Tapete, ihre aesthetische Bedeutung u. Techn.
Darstellung, sowie kurze Beschreibung der Buntpapierfabrik. 1882.

SILCOX.--Manufacture of Paper Barrels. Vienna Exhibition, 1873. U.S.A.
Reports, ii.

SMEE, A.--Report on Vegetable Parchment (Gaine's Patent, No. 2834 of
1853). _London_, 8^o, 1858.

THON, C. F. G.--Der Fabrikant bunter Papiere, 3te Aufl. _Weimar_, 12^o,
1844.

WEICHELT, A.--Buntpapier-Fabrikation. _Berlin_, 8^o, 1903.

WHITING PAPER CO.--How Paper is Made. _Holyoke, Mass._, 32^o, 1893.

WINZER, A.--Die Bereitung und Benutzung der Papiermaché und ähnlicher
Kompositionen, 3te Aufl. _Weimar_, 12^o, 1884.

    Ditto, 4th edition, 1907.

WOOLNOUGH, C. W.--The Whole Art of Marbling, as applied to Paper, Book
Edges, etc. _London_, 8^o, 1881.

WYATT, SIR M. D.--Report on Paper-hangings. Paris Univ. Exhibition,
1867. Brit. Comm. Report, Vol. II. 8^o, 1867.


STATISTICS AND VARIOUS.

AKESSON.--Lexikon der Papier-Industrie. Deutsch-Englisch-Französisch,
2te Aufl. 1905.

ARCHER, T. C.--British Manufacturing Industries. Vol. 15. Industrial
Statistics. _London._

BARTH, E.--Arbeitsregeln für Fabriken mit besonderer Berücksichtigung
von Papierfabriken. _Karlsruhe_, 1897.

BAUDISCH, J.--Einige ins Papierfach schlagende Berechnungen.
_Biberach_, 1893.

DYSON.--Mosely Commission Report. _Manchester_, 1903.

ERMEL.--Rapport sur le matériel et les procédés de la papeterie, etc.
Paris Univ. Exhibition, 1878. Rapports. Classe 60. 8^o, 1881.

FOREIGN OFFICE, No. 4 (1871).--Reports on the Manufacture of Paper in
Japan. _London_, fol., 1871.

GEYER, A.--Registry of Water-marks and Trade-marks. Compiled from the
American Paper Trade (2nd edition). _New York_, 1898.

    Ditto, 5th edition, 1903.

GRATIOT, A.--Description de la papeterie d'Essonnes, London
International Exhibition of 1851, Prospectuses of Exhibitors. Vol. 2.
8^o, 1851.

KRAWANY, F.--Warte der Papier-Halbstoff- und Pappenfabriken
Oesterreich-Ungarns. 1905.

LANDGRAF, J.--Papier-Holzschliff und seine Zollpolitische Würdigung.
_Mannheim._

LOCKWOOD & CO.--American Dictionary of Printing and Bookmaking. _New
York_, 1895.

LUDWIG, G.--Trockengehalts-Tabellen. _Pirna_, 1897.

MACNAUGHTON, J.--Factory Book-keeping for Paper Mills. 1900.

MAHRLEN.--Papierfabrikation, im Königr. Württemberg (im Jahre 1860).
_Stuttgart_, 8^o, 1861.

MARR, D.--Kosten der Betriebskräfte bei 1-24 stündiger Arbeitszeit
täglich und unter Berücksichtigung des Aufwandes für die Heizung.
_München_ u. _Berlin_.

MELNIKOFF, N.--Lehrbuch der Papier-Holzschliff, Zellstoff und
Pappenfabrikation. _Petersburg_, 1905.

MELNIKOFF, N.--Kleines Handbuch Papierfabrikation. _Petersburg_, 1906.

MELNIKOFF, N.--Geschichte, Statistik u. Literatur der Papierindustrie
nebst russischen Wasserzeichen. _Petersburg_, 1906.

MUNSELL, J.--Chronology of Paper-making. _Albany_, 8^o, 1857.

    Ditto, 4th edition, 1870.

MUNSELL, J.--Chronology of the Origin and Progress of Paper and
Paper-making. _Albany_, 1876.

MUNSELL, J.--Observations Illustrative of the Operation of the Duties
on Paper. _London_, 8^o, 1836.

MUNSELL, J.--Matériel et procédés de la papeterie, etc., 1889. Rapports
du Jury. Classe 58. 8^o, 1889.

PARIS UNIV. EXHIBITION.--Papiers peints, 1889. Rapports du Jury. Classe
21. 8^o, 1891.

PASSERAT, A. L.--Barème complet pour papeteries. _Paris._

PATENTS.--Patent Abridgments. Class 96. Patent Office Abstracts on
Paper-making. From 1855 to date.

ROULHAC.--Papeterie. Paris Univ. Exhibition, 1867. Rapports du Jury.
Classe 7, sect. 1. 8^o, 1868.

SAMPSON, J. T.--Paper-staining. Mansion House Committee. Artisans'
Reports, Paris Exhibition. 8^o, 1889.

TREASURY.--Report of the Excise Commission. 1835.

VOGEL, K.--Papierindustrie, etc., Auf der Weltausstellung in Chicago.
Chicago Exhibition, 1893. Austrian Central Committee. Officieller
Bericht. Heft iv. 8^o, 1894.

VOIGT, G.--Papiergewichtstabellen. _Merseburg_, 1894.

WARD, SIR W.--Report on German Paper-making Industry. Parliamentary
Paper, 1905.

WATER-MARKS.--Water-marks and Trade-marks Registry (2nd ed.). _New
York_, 16^o, 1898.


WOOD PULP AND PULP WOOD.

BRITISH AND COLONIAL PRINTER.--History of Wood Pulp. Vol. 8. 1882.

DUNBAR.--Wood Pulp and Wood Pulp Papers.

FITTICA, DR. F.--Geschichte der Sulfitzellstoff-Fabrikation. _Leipzig_,
1901.

FITTICA, DR. F.--Forestry and Forest Products. [Edinburgh Forestry
Exhibition. 1884.]

GOTTSTEIN.--Holzzellstoff in seiner Anwendung für die Papier- und
Textil-Industrie und die bei seiner Herstellung entstehenden Abwässer.
1904.

GRIFFIN, M. L.--Sulphite Processes. American Society C. E. 417. 1889.

HARPER, W.--Utilisation of Wood Waste by Distillation. _U.S.A._, 1907.

HARPF, A.--Die Erzeugung von Holzschliff und Zellstoff. _Wien_, 1901.

HARPF, A.--Flüssiges Schwefeldioxyd. _Stuttgart_, 1901.

HUBBARD.--Utilisation of Wood Waste. 1902.

JOHNSON, G.--Wood Pulp of Canada. 1902-08. Yearly.

MICHAELIS, O. E.--Lime Sulphite Fibre Manufacture in the United States.
With Remarks on the Chemistry of the Processes, by M. L. Griffin
(excerpt). _New York_, 8^o, 1889.

PHILLIPS, S. C.--Uses of Wood Pulp. 1904.

ROSENHEIM, G. M.--Die Holzcellulose. _Berlin_, 1878.

SCHUBERT, M.--Die Holzstoff oder Holzschliff-Fabrikation. 1898.

SCHUBERT, M.--Die Cellulosefabrikation (Zellstofffabrikation).
Praktisches Handbuch für Papier- u. Cellulosetechniker. 1906.

SINDALL, R. W.--The Sampling of Wood Pulp. _London_, 8^o, 1901.

VEITCH, L. P.--Chemical Methods for Utilising Wood. U.S.A. Department
of Agriculture. 1907.

VEITCH, L. P.--Wood Pulp, Uses of. U.S.A. Consular Reports, vol. xix.

       *       *       *       *       *

BANKS AND CRATE.--Pulpwood Problems. Letters to the _Globe_, Toronto,
Canada. 1907.

GAMBLE, J.--Indian Timbers.

GRAVES.--The Woodsman's Handbook. _U.S.A._

PINCHOTT, G.--Forestry Primer. _U.S.A._, 1900.

PINCHOTT, G.--The Adirondack Spruce. _U.S.A._

RATTRAY, J., AND MILL, H. R.--Forestry and Forestry Products.
_Edinburgh_, 1885.

SCHLICH.--Forestry Manual.

       *       *       *       *       *

Some more or less interesting articles on "Paper" will be found in the
following encyclopædias, etc.:--

  DATE.
  1738.  Chambers's Encyclopædia.
  1757.  Barrow. Dictionary of Arts.
  1759.  New. Universal History of Arts.
  1770.  Royal Dictionary of Arts.
  1788.  Howard. A Royal Encyclopædia.
  1806.  Gregory. A Dictionary of Arts and Sciences.
  1807.  Encyclopædia Perthensis.
  1809.  Nicholson. The British Encyclopædia.
  1813.  Martin. Circle of the Mechanical Arts.
  1813.  Pantologia.
  1819.  Rees' Cyclopædia.
  1821.  Encyclopædia Londoniensis.
  1827.  Jamieson's Dictionary.
  1828.  Oxford Encyclopædia.
  1829.  The London Encyclopædia.
  1830.  Edinburgh Encyclopædia.
  1833.  Phillip's Dictionary of Arts.
  1835.  Partington. British Cyclopædia.
  1836.  Archæologia, vol. xxvi.
  1836.  Barlow. Encyclopædia of Arts.
  1840.  The Penny Encyclopædia.
  1845.  Encyclopædia Metropolitana.
  1848.  Useful Arts of Great Britain. S.P.C.K
  1851.  Knight's Cyclopædia of Industry.
  1855.  Appleton's Dictionary of Mechanics.
  1860.  Hebert. Mechanic's Encyclopædia.
  1861.  Knight's English Cyclopædia.
  1861.  New American Cyclopædia.
  1866.  Tomlinson's Dictionary of Arts.
  1871.  Yeats. The Technical History of Commerce.
  1874.  Clarke's Practical Magazine.
  1875.  Ure's Dictionary of Arts.
  1875.  Globe Cyclopædia.
  1876.  American Mechanical Dictionary.
  1877.  Johnson's Universal Cyclopædia.
  1880.  Wylde. Industries of the World.
  1882.  Spon's Encyclopædia of Manufactures.
  1886.  Encyclopædia Britannica.
  1889.  Chambers's Encyclopædia.
  1889.  Blaikie. Modern Cyclopædia.
  1890.  Popular Encyclopædia.
  1892.  Spon's Workshop Receipts.
  1903.  Gilman. International Encyclopædia.
  1904.  Encyclopædia Americana.
  1904.  Tweney's Technological Dictionary.


NEWSPAPERS.


_England._

Papermaker and British Paper Trade Journal. S. C. Phillips, London.

Papermakers' Circular. Dean & Son, London.

Papermakers' Monthly Journal. Marchant, Singer & Co., London.

Paper Box and Bag Maker. S. C. Phillips, London.

Papermaking. London.

The Paper and Printing Trades' Journal. London.

World's Paper Trade Review. W. J. Stonhill, London.


_Canada._

Pulp and Paper Magazine. Biggar-Wilson, Ltd., Toronto.


_United States of America._

American Bookmaker. Howard Lockwood & Co., New York.

The Paper Trade. Chicago.

The Stationer. Howard Lockwood & Co., New York.

Paper Mill and Wood Pulp News. L. D. Post & Co., New York.

Paper Trade Journal. Howard Lockwood & Co., New York.

The Paper World. C. W. Bryan & Co., Holyoke, Mass.


_France._

Bulletin Journal des Fabricants de Papier. Paris.

Journal des Papetiers. M. Edmond Rousset, Paris.

Le Moniteur de la Papeterie Française. Paris.

La Papeterie. Paris.

La Revue de la Papeterie Française et Étrangère. M. Edmond Rousset,
Paris.

Le Papier. H. Everling, Paris.


_Germany._

Centralblatt für die Österreichisch-Ungarische Papierindustrie. Adolf
Hladufka, Wien.

Der Papierfabrikant. Otto Elsner, Berlin.

Der Papier-Markt. Carl Dobler, Frankfurt a. Main.

Deutsche Papier- und Schreibwarenzeitung. S. Richter, Berlin.

Die Postkarte. Gustav Fahrig, Leipzig.

Export-Journal. G. Hedeler, Leipzig.

Holzstoff-Zeitung. Camillo Drache, Dresden.

Papierhändler Zeitung für Österreich-Ungarn. Wien.

Papier-Industrie. Berlin.

Papier- und Schreibwaren-Zeitung. Wien.

Papier-Zeitung. C. Hofmann, Berlin.

Schweizer Graphischer Central-Anzeiger. H. Keller, Luzern.

Wochenblatt für Papierfabrikation. Guntter-Staib Biberach (Württ).

Wochenschrift für den Papier- und Schreibwarenhandel. Dr. H.
Hirschberg, Berlin.


ANALYSIS, TECHNOLOGY.

BEADLE AND STEVENS.--Blotting paper, nature of absorbency. 1905.

WINKLER.--Estimation of Moisture in Wood-pulp. 1902. Translated by Dr.
H. P. Stevens.

HAUPTVERSAMMLUNG.--Published annually by the Verein der Zellstoff- und
Papier-Chemiker. _Berlin_, 1907 et.


FIBRES, etc.

DODGE, C. R.--Catalogue of useful Fibre-plants of the World. Report No.
9. Dept. of Agriculture. _U.S.A._, 1897.

DUCHESNE, E. A.--Répertoire des plantes utiles et des plantes
vénéneuses du globe, etc. _Bruxelles_, 1846.

GABALDE, B.--Essai sur le bananier et ses applications à la fabrication
de papier. 1843.

MONTESSUS DE BALLORE.--Alfa et papier d'Alfa. 1908.

PECHEUX.--Les textiles, les tissus, le papier. 6 pp. _Paris_, 1907.

RENOUARD.--Études sur les fibres textiles. _Paris._

RENOUARD.--Les fibres textiles de l'Algérie. _Paris._

RIVIERE, AUGUSTE ET CHARLES.--"Les Bambous." Société d'Acclimatation.
_Paris._

RICHMOND, G. F.--Philippine Fibres and Fibrous Substances. _Manila_,
Bureau of Printing, 1906.


HISTORICAL.

BRIQUET, C. M.--Recherches sur les premiers Papiers employés du X^e au
XIV^e siècle. pp. 77. _Paris_, 1886.

BRIQUET, C. M.--De la valeur des Filigranes du Papier comme moyen de
déterminer l'âge de documents. pp. 13. _Genève_, 1892.

BRIQUET, C. M.--La Légende paléographique du Papier de Coton. pp. 18.
_Genève_, 1884.

BRIQUET, C. M.--Lettre sur les Papiers usités en Sicile à l'occasion de
deux manuscrits en papier dit le coton. 16 pp. _Palermo_, 1892.

DESMAREST, N.--Art de la Papeterie. _Paris_, 1879.

DELON, C.--Histoire d'un livre. _Paris_, 1879.

DIDOT, A. F.--Le centenaire de la Machine à Papier continu. pp. 79.
_Paris_, 1900.

DICKINSON, J.--Dickinson's Paper Mills. _Calcutta_, 1884.

GIRARD, A.--Le Papier. Ses ancêtres. Son histoire. _Lille_, 1892.

JULIEN, S.--Description des procédés chinois pour la fabrication du
papier. Traduit de l'ouvrage chinois par Thien-Kong-Kha-We. 1840.

KAY, J.--Paper, its history. pp. 100. _London_, 1893.

LEMPERTZ, H.--Beiträge zur Geschichte des Leinen-Papiers. _Köln_, 1891.


PAPER MANUFACTURE.

BORY, P.--Les Métamorphoses d'un Chiffon. _Abbeville_, 1897.

CHABROL, L.--La Réglementation du Travail dans l'industrie du papier.
pp. 168. _Paris_, 1901.

DEMUTH, F.--Die Papier-Fabrikation. 1903.

DEMUTH, F.--Die Störungen im deutschen Wirtschaftsleben 1900.
_Leipzig_, 1903.

LIMOGE.--Cercles d'Études commerciales, Le Papier. pp. 140. _Limoge_,
1892.


PAPER, SPECIAL KINDS.

SPALDING AND HODGE.--Printing papers; a handbook. _London_, 1905.


STATISTICS, etc.

BEADLE, C.--Development of Water-marking. _London_, 1906 (Society of
Arts).

DUMERCY.--Bibliographie de la Papeterie. pp. 28. _Bruxelles_, 1888.

BRUCE, H.--Gladstone and Paper Duties. _Edinburgh_, 1885.

ELLIS, J. B.--Hints for the Paper Warehouse. _Leeds_, 1887.

WEBSTER, J.--Synopsis of Sizes of Paper. _Southport_, 1889.

WHITSON, W.--The Concise Paper Calculator. _Edinburgh_, 1903.


WOOD PULP, etc.

DROPISCH, B.--Holzstoff und Holzcellulose. _Weimar_, 1879.




INDEX


  Acid dyes, 201
    in papers, 239
    size, 170

  Agave, 40

  Alum, 167, 168

  Aniline dyes, 201
    sulphate, 121

  Animal size, 63, 164

  Antichlors, 163

  Art paper, 142
    imitation, 145
    testing, 147

  Asbestos, 174

  Ash in paper, 171


  Backwater, 120, 205

  Bagasse, 41

  Bamboo, 43

  Barker, 97

  Beating engines, 186
    patents, 192
    power consumed, 191

  Beating, conditions of, 197
    early methods of, 176
    experiments in, 179
    process of, 58, 175

  Bibliography, 253

  Bisulphite of lime, 159

  Bleaching, 57, 83
    powder, 161

  Blue prints, 140

  Board machine, 132, 135

  Boards, manufacture of, 131
    duplex, 132, 134

  Book papers, quality of, 246

  Books, decay of, 237

  Brown papers, 127


  Carbonic acid recorder, 215

  Casein, 165, 235

  Caustic soda, 81, 155

  Cellulose, 21
    derivatives of, 29
    hydrolysis of, 27, 229
    oxidation of, 28
    percentage of, in plants, 23
    properties of, 26

  Chemical residues in paper, 238
    wood pulp, 104

  Chemicals, 153

  China clay, 117, 150, 171, 204, 234

  Coal consumption, 214

  Coated paper, 142

  Cold ground pulp, 100

  Colophony, 169

  Colour of paper, fading of, 203, 241
    matching, 205
    unevenness of, 203

  Colouring of paper pulp, 199
    analysis of, 206

  Cotton, 22, 69

  Cyanotype papers, 140

  Cylinder machine, 131


  Density of paper, 181

  Deterioration of paper, 228, 246

  Digesters, 52, 89, 109

  Dilution tables, 157, 163

  Duplex boards, 134

  Dyeing of paper, 199


  Eibel patent, 223

  Electrical power, 219

  Electrolytic bleaching, 57

  Engine sizing, 117, 167

  Esparto, 72
    bleaching of, 83
    composition of, 73
    test for, in papers, 87
    yield of, 77

  Evaporation apparatus, 76, 79
    tables, 81


  Featherweight papers, 232

  Fibres for paper-making, 38
    examination of, 43
    reagents for staining, 71

  Flax, 40

  Fourdrinier machine, early, 16

  French chalk, 173


  Gas producer, 218

  Gelatine, 63, 164, 237

  Glue, 137, 142, 235

  Grinders, 100


  History of paper, 1

  Hoernle, 7

  Hollander, 16, 59, 176, 185

  Hot ground pulp, 100


  Imitation art paper, 145, 235
    Kraft paper, 129
    parchment, 137

  Improvements in paper-making, 214

  Iron in paper, 229


  Kraft papers, 128


  Laid papers, 66

  Lime, 52, 157
    bisulphite, 159
    sulphate, 173

  Linen fibre, 70

  Loading, 171


  M. G. caps, 130

  Machinery, 214, 224

  Manila paper, 127

  Mechanical pulp, 95
    detection of, 121

  Metanil yellow, 122

  Middles, 134

  Mitscherlich pulp, 107

  Moisture, influence of, 243

  Multiple effect evaporation, 79


  Neutral size, 169

  Newspaper, 116, 215


  Output of a paper machine, 122


  Paper, art, 142
    ash in, 171
    brown, 127
    bulk of, 231
    chemical residues in, 238
    clay in, 234
    colour of, 199, 241
    colour in, analysis of, 207
    deterioration of, 229
    fibres for, 38
    history of, 1, 5
    iron in, 239
    permanence of, 230
    rags used for, 47
    sizing of, 63
    special kinds of, 137
    standards of quality, 246
    strength, of, 184, 231
    surface of, 233
    volume composition of, 233

  Paper machine, early, 16
    output of, 122

  Papier-maché, 150

  Papyrus, 2, 42

  Paraffin paper, 148

  Parchment, 4
    paper, 137

  Peat, 41

  Phloroglucine, 121

  Pigments, 199

  Porion evaporator, 76

  Presse-pâte, 86

  Prussian blue, 200


  Rag paper, manufacture of, 47
    origin of, 5

  Rags, bleaching, 55
    boiling, 51
    classification, 48
    sorting, 48

  Ramie, 40

  Records, early, 1

  Recovered ash, 158

  Recovery processes, 78, 113

  Refiners, 90

  Rope browns, 127

  Rosin size, 117, 169, 236


  Screens, 102

  Sealings, 129

  Shrinkage of paper, 181

  Sizing of paper, 63, 117, 167

  Society of Arts, 246

  Soda, 153

  Soda pulp, 107, 113
    recovery, 78
    silicate of, 166, 171

  Softening of water, 216

  Spent liquors, 78, 113

  Staining reagents for fibres, 71

  Standards of quality, 246, 248, 250

  Starch, 166, 237

  Stationery Office, 248

  Stone beater rolls, 189

  Straw, 88

  Sulphate pulp, 107

  Sulphite pulp, 107

  Sulphites, 159, 163

  Supercalender, 65

  Superheated steam, 218


  Tinfoil paper, 148

  Transfer paper, 149


  Ultramarine, 199


  Volume composition of paper, 233

  Vulcanised fibre, 139


  Water softening, 216

  Watermarks, 67

  Wavy edges, 243

  Waxed paper, 147

  Wet press machine, 103

  Wiesner, 6

  Willesden paper, 139

  Wood, 22
    pulp, 95
      chemical, 104
      mechanical, 95
      soda, 107, 113
      sulphite, 107

  Wove papers, 66

  Wrappers, 127


BRADBURY, AGNEW, & CO. LD., PRINTERS, LONDON AND TONBRIDGE.




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  $Coal.$ By JAMES TONGE, M.I.M.E., F.G.S., etc. (Lecturer on Mining at
      Victoria University, Manchester). With 46 Illustrations, many of
      them showing the Fossils found in the Coal Measures.

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    LIST OF CONTENTS: Introductory. Iron Ores. Combustible and other
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  $Natural Sources of Power.$ By $Robert S. Ball$, B.Sc., A.M.Inst.C.E.
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      Acceleration. Energy. Power. Introductory Water Power and Methods
      of Measuring. Application of Water Power to the Propulsion of
      Machinery. The Hydraulic Turbine. Various Types of Turbine.
      Construction of Water Power Plants. Water Power Installations.
      The Regulation of Turbines. Wind Pressure, Velocity, and Methods
      of Measuring. The Application of Wind Power to Industry. The
      Modern Windmill. Constructional Details. Power of Modern
      Windmills. Appendices A, B, C. Index.

Two departments of Engineering and their applications to industry form
the subject of this volume: the "natural" sources of water and wind
power which supply mechanical energy without any intermediate stage of
transformation. Most people will be surprised at the extent to which
these natural power producers are used. The widespread application
of water power is generally known, but it is interesting to learn
that the demand for windmills was never so great as it is to-day, and
there are signs of abnormal expansion in the direction of their useful
application in the great agricultural countries of the world. Though
primarily of importance to the engineer, this work will be of great
interest to every manufacturer who in economizing his means of power
production can take the natural forces that lie to his hand and harness
them in his service. The author is the son of Sir Robert Ball, the
eminent mathematician and astronomer.


  $Liquid and Gaseous Fuels, and the Part they play in Modern Power
      Production.$ By Professor VIVIAN B. LEWES, F.I.C., F.C.S.,
      Prof. of Chemistry, Royal Naval College, Greenwich. With 54
      Illustrations.

    LIST OF CONTENTS: Lavoisier's Discovery of the Nature of
      Combustion, etc. The Cycle of Animal and Vegetable Life. Method
      of determining Calorific Value. The Discovery of Petroleum in
      America. Oil Lamps, etc. The History of Coal Gas. Calorific Value
      of Coal Gas and its Constituents. The History of Water Gas.
      Incomplete Combustion. Comparison of the Thermal Values of our
      Fuels, etc. Appendix. Bibliography. Index.

The subject of this book has, during the last decade, assumed such
importance that it is hoped this account of the history and development
of the use of various forms of combustible liquids and gases for the
generation of energy may do some service in its advancement.


  $Electric Power and Traction.$ By F. H. DAVIES, A.M.I.E.E. With 66
      Illustrations.

    LIST OF CONTENTS: Introduction. The Generation and Distribution of
      Power. The Electric Motor. The Application of Electric Power.
      Electric Power in Collieries. Electric Power in Engineering
      Workshops. Electric Power in Textile Factories. Electric Power
      in the Printing Trade. Electric Power at Sea. Electric Power on
      Canals. Electric Traction. The Overhead System and Track Work.
      The Conduit System. The Surface Contact System. Car Building and
      Equipment. Electric Railways. Glossary. Index.

The majority of the allied trades that cluster round the business of
electrical engineering are connected in some way or other with its
power and traction branches. To members of such trades and callings, to
whom some knowledge of applied electrical engineering is desirable if
not strictly essential, the book is particularly intended to appeal.
It deals almost entirely with practical matters, and enters to some
extent into those commercial considerations which in the long run must
overrule all others.


  $Town Gas and its Uses for the Production of Light, Heat, and Motive
      Power.$ By W. H. Y. WEBBER, C.E. With 71 Illustrations.

    LIST OF CONTENTS: The Nature and Properties of Town Gas. The
      History and Manufacture of Town Gas. The By-Products of Coal Gas
      Manufacture. Gas Lights and Lighting. Practical Gas Lighting. The
      Cost of Gas Lighting. Heating and Warming by Gas. Cooking by Gas.
      The Healthfulness and Safety of Gas in all its uses. Town Gas for
      Power Generation, including Private Electricity Supply. The Legal
      Relations of Gas Suppliers, Consumers, and the Public. Index.

The "country," as opposed to the "town," has been defined as "the parts
beyond the gas lamps." This book provides accurate knowledge regarding
the manufacture and supply of town gas and its uses for domestic and
industrial purposes. Few people realize the extent to which this great
industry can be utilized. The author has produced a volume which will
instruct and interest the generally well informed but not technically
instructed reader.


  $Electro-Metallurgy.$ By J. B. C. KERSHAW, F.I.C. With 61
      Illustrations.

    CONTENTS: Introduction and Historical Survey. Aluminium.
      Production. Details of Processes and Works. Costs. Utilization.
      Future of the Metal. Bullion and Gold. Silver Refining Process.
      Gold Refining Processes. Gold Extraction Processes. Calcium
      Carbide and Acetylene Gas. The Carbide Furnace and Process.
      Production. Utilization. Carborundum. Details of Manufacture.
      Properties and Uses. Copper. Copper Refining. Descriptions
      of Refineries. Costs. Properties and Utilization. The Elmore
      and similar Processes. Electrolytic Extraction Processes.
      Electro-Metallurgical Concentration Processes. Ferro-alloys.
      Descriptions of Works. Utilization. Glass and Quartz Glass.
      Graphite. Details of Process. Utilization. Iron and Steel.
      Descriptions of Furnaces and Processes. Yields and Costs.
      Comparative Costs. Lead. The Salom Process. The Betts Refining
      Process. The Betts Reduction Process. White Lead Processes.
      Miscellaneous Products. Calcium. Carbon Bisulphide. Carbon
      Tetra-Chloride. Diamantine. Magnesium. Phosphorus. Silicon and
      its Compounds. Nickel. Wet Processes. Dry Processes. Sodium.
      Descriptions of Cells and Processes. Tin. Alkaline Processes
      for Tin Stripping. Acid Processes for Tin Stripping. Salt
      Processes for Tin Stripping. Zinc. Wet Processes. Dry Processes.
      Electro-Thermal Processes. Electro-Galvanizing. Glossary. Name
      Index.

The subject of this volume, the branch of metallurgy which deals
with the extraction and refining of metals by aid of electricity,
is becoming of great importance. The author gives a brief and clear
account of the industrial developments of electro-metallurgy, in
language that can be understood by those whose acquaintance with
either chemical or electrical science may be but slight. It is a
thoroughly practical work descriptive of apparatus and processes,
and commends itself to all practical men engaged, in metallurgical
operations, as well as to business men, financiers, and investors.


  $Radio-Telegraphy.$ By C. C. F. MONCKTON, M.I.E.E. With 173 Diagrams
      and Illustrations.

    CONTENTS: Preface. Electric Phenomena. Electric Vibrations.
      Electro-Magnetic Waves. Modified Hertz Waves used in
      Radio-Telegraphy. Apparatus used for Charging the Oscillator.
      The Electric Oscillator: Methods of Arrangement, Practical
      Details. The Receiver: Methods of Arrangement, The Detecting
      Apparatus, and other details. Measurements in Radio-Telegraphy.
      The Experimental Station at Elmers End: Lodge-Muirhead System.
      Radio-Telegraph Station at Nauen: Telefunken System. Station at
      Lyngby: Poulsen System. The Lodge-Muirhead System, the Marconi
      System, Telefunken System, and Poulsen System. Portable Stations.
      Radio-Telephony. Appendices: The Morse Alphabet. Electrical Units
      used in this Book. International Control of Radio-Telegraphy.
      Index.

The startling discovery twelve years ago of what is popularly known
as Wireless Telegraphy has received many no less startling additions
since then. The official name now given to this branch of electrical
practice is Radio-Telegraphy. The subject has now reached a thoroughly
practicable stage, and this book presents it in clear, concise form.
The various services for which Radio-Telegraphy is or may be used are
indicated by the author. Every stage of the subject is illustrated by
diagrams or photographs of apparatus, so that, while an elementary
knowledge of electricity is presupposed, the bearings of the subject
can be grasped by every reader. No subject is fraught with so many
possibilities of development for the future relationships of the
peoples of the world.


  $India-Rubber and its Manufacture, with Chapters on Gutta-Percha
      and Balata.$ By H. L. TERRY, F.I.C., Assoc.Inst.M.M. With
      Illustrations.

    LIST OF CONTENTS: Preface. Introduction: Historical and General.
      Raw Rubber. Botanical Origin. Tapping the Trees. Coagulation.
      Principal Raw Rubbers of Commerce. Pseudo-Rubbers. Congo Rubber.
      General Considerations. Chemical and Physical Properties.
      Vulcanization. India-rubber Plantations. India-rubber
      Substitutes. Reclaimed Rubber. Washing and Drying of Raw Rubber.
      Compounding of Rubber. Rubber Solvents and their Recovery.
      Rubber Solution. Fine Cut Sheet and Articles made therefrom.
      Elastic Thread. Mechanical Rubber Goods. Sundry Rubber Articles.
      India-rubber Proofed Textures. Tyres. India-rubber Boots and
      Shoes. Rubber for Insulated Wires. Vulcanite Contracts for
      India-rubber Goods. The Testing of Rubber Goods. Gutta-Percha.
      Balata. Bibliography. Index.

Tells all about a material which has grown immensely in commercial
importance in recent years. It has been expressly written for the
general reader and for the technologist in other branches of industry.


  $Glass Manufacture.$ By WALTER ROSENHAIN, Superintendent of the
      Department of Metallurgy in the National Physical Laboratory,
      late Scientific Adviser in the Glass Works of Messrs. Chance
      Bros. and Co. With Illustrations.

    CONTENTS: Preface. Definitions. Physical and Chemical Qualities.
      Mechanical, Thermal, and Electrical Properties. Transparency and
      Colour. Raw materials of manufacture. Crucibles and Furnaces for
      Fusion. Process of Fusion. Processes used in Working of Glass.
      Bottle. Blown and Pressed. Rolled or Plate. Sheet and Crown.
      Coloured. Optical Glass: Nature and Properties, Manufacture.
      Miscellaneous Products. Appendix. Bibliography of Glass
      Manufacture. Index.

This volume is for users of glass, and makes no claim to be an
adequate guide or help to those engaged in glass manufacture itself.
For this reason the account of manufacturing processes has been
kept as non-technical as possible. In describing each process the
object in view has been to give an insight into the rationale of each
step, so far as it is known or understood, from the point of view of
principles and methods rather than as mere rule of thumb description
of manufacturing manipulations. The processes described are, with the
exception of those described as obsolete, to the author's definite
knowledge, in commercial use at the present time.


  $Precious Stones.$ By W. GOODCHILD, M.B., B.Ch. With 42
      Illustrations. $With a Chapter on Artificial Stones.$ By ROBERT
      DYKES.

    LIST OF CONTENTS: Introductory and Historical. Genesis of Precious
      Stones. Physical Properties. The Cutting and Polishing of Gems.
      Imitation Gems and the Artificial Production of Precious Stones.
      The Diamond. Fluor Spar and the Forms of Silica. Corundum,
      including Ruby and Sapphire. Spinel and Chrysoberyl. The
      Carbonates and the Felspars. The Pyroxene and Amphibole Groups.
      Beryl, Cordierite, Lapis Lazuli and the Garnets. Olivine, Topaz,
      Tourmaline and other Silicates. Phosphates, Sulphates, and Carbon
      Compounds.

An admirable guide to a fascinating subject.


  $Patents, Designs and Trade Marks: The Law and Commercial Usage.$
      By KENNETH R. SWAN, B.A. (Oxon.), of the Inner Temple,
      Barrister-at-Law.

    CONTENTS: Table of Cases Cited--_Part I.--Letters Patent._
      Introduction. General. Historical. I., II., III. Invention,
      Novelty, Subject Matter, and Utility the Essentials of Patentable
      Invention. IV. Specification. V. Construction of Specification.
      VI. Who May Apply for a Patent. VII. Application and Grant.
      VIII. Opposition. IX. Patent Rights. Legal Value. Commercial
      Value. X. Amendment. XI. Infringement of Patent. XII. Action for
      Infringement. XIII. Action to Restrain Threats. XIV. Negotiation
      of Patents by Sale and Licence. XV. Limitations on Patent Right.
      XVI. Revocation. XVII. Prolongation. XVIII. Miscellaneous.
      XIX. Foreign Patents. XX. Foreign Patent Laws: United States
      of America. Germany. France. Table of Cost, etc., of Foreign
      Patents. APPENDIX A.--1. Table of Forms and Fees. 2. Cost of
      Obtaining a British Patent. 3. Convention Countries. _Part
      II.--Copyright in Design._ Introduction. I. Registrable Designs.
      II. Registration. III. Marking. IV. Infringement. APPENDIX
      B.--1. Table of Forms and Fees. 2. Classification of Goods.
      _Part III.--Trade Marks._ Introduction. I. Meaning of Trade
      Mark. II. Qualification for Registration. III. Restrictions on
      Registration. IV. Registration. V. Effect of Registration. VI.
      Miscellaneous. APPENDIX C.--Table of Forms and Fees. INDICES. 1.
      Patents. 2. Designs. 3. Trade Marks.

This is the first book on the subject since the New Patents Act. Its
aim is not only to present the existing law accurately and as fully as
possible, but also to cast it in a form readily comprehensible to the
layman unfamiliar with legal phraseology. It will be of value to those
engaged in trades and industries where a knowledge of the patenting
of inventions and the registration of trade marks is important. Full
information is given regarding patents in foreign countries.


  $The Book; Its History and Development.$ By CYRIL DAVENPORT, V.D.,
      F.S.A. With 7 Plates and 126 Figures in the text.

    LIST OF CONTENTS: Early Records. Rolls, Books and Book bindings.
      Paper. Printing. Illustrations. Miscellanea. Leathers. The
      Ornamentation of Leather Bookbindings without Gold. The
      Ornamentation of Leather Bookbindings with Gold, Bibliography.
      Index.

The romance of the Book and its development from the rude inscriptions
on stone to the magnificent de Luxe tomes of to-day have never been so
excellently discoursed upon as in this volume. The history of the Book
is the history of the preservation of human thought. This work should
be in the possession of every book lover.


Van Nostrand's "Westminster" Series

LIST OF NEW AND FORTHCOMING VOLUMES.

  $Timber.$ By J. R. BATERDEN, A.M.I.C.E.

  $Steam Engines.$ By J. T. ROSSITER, M.I.E.E., A.M.I.M.E.

  $Electric Lamps.$ By MAURICE SOLOMON, A.C.G.I., A.M.I.E.E.

  $The Railway Locomotive.$ By VAUGHAN PENDRED, M.I.Mech.E.

  $Leather.$ By H. GARNER BENNETT.

  $Pumps and Pumping Machinery.$ By JAMES W. ROSSITER, A.M.I.M.E.

  $Workshop Practice.$ By Professor G. F. CHARNOCK, A.M.I.C.E., M.I.M.E.

  $Textiles and their Manufacture.$ By ALDRED BARKER, M.Sc.

  $Gold and Precious Metals.$ By THOMAS K. ROSE, D.Sc., of the Royal
      Mint.

  $Photography.$ By ALFRED WATKINS, Past President of the Photographic
      Convention.

  $Commercial Paints and Painting.$ By A. S. JENNINGS, Hon. Consulting
      Examiner, City and Guilds of London Institute.

  $Ornamental Window Glass Work.$ By A. L. DUTHIE.

  $Brewing and Distilling.$ By JAMES GRANT, F.C.S.

  $Wood Pulp and Its Applications.$ By C. F. CROSS, E. J. BEVAN and R.
      W. SINDALL.

  $The Manufacture of Paper.$ By R. W. SINDALL.


                     D. VAN NOSTRAND COMPANY
                  _Publishers and Booksellers_
            23, MURRAY AND 27, WARREN STREETS, NEW YORK.


  +--------------------------------------------------------------------+
  | Transcriber's Notes                                                |
  |                                                                    |
  | The following inconsistencies were kept:                           |
  |                                                                    |
  | 500-K.W. -- 1000 K.W.                                              |
  | back-water -- backwater                                            |
  | bed-plate -- bedplate                                              |
  | Buntpapier-Fabrikation -- Buntpapierfabrikation                    |
  | cc. -- c.c.                                                        |
  | coloration -- colouring                                            |
  | conical-shaped -- conical shaped                                   |
  | Cwts. -- cwts.                                                     |
  | Darthford (cited) -- Dartford                                      |
  | drum washers -- drum-washer                                        |
  | economiser -- economizing                                          |
  | edge runner -- edge-runner                                         |
  | gesamte -- gesammten                                               |
  | grams -- grammes                                                   |
  | h.p. -- h.-p.                                                      |
  | Holzschliffes -- Holzschliffs                                      |
  | Hydral-Cellulose -- hydra-cellulose                                |
  | India-Rubber -- India-rubber                                       |
  | midfeather -- mid-feather                                          |
  | Mitteilungen -- Mittheilungen                                      |
  | oval shaped -- oval-shaped                                         |
  | Oxy-Cellulose -- Oxy-cellulose                                     |
  | oxy-cellulose -- oxycellulose                                      |
  | Paper-maker -- Papermaker                                          |
  | Papiererzeugung -- Papier-Erzeugung                                |
  | Papierfabrikation -- Papier-Fabrikation                            |
  | per cent. -- per Cent.                                             |
  | realise -- realize                                                 |
  | Schreibwarenzeitung -- Schreibwaren-Zeitung                        |
  | sugarcane -- sugar-cane                                            |
  | utilisation -- utilization                                         |
  | utilised -- utilized                                               |
  | Vulcanised -- Vulcanization                                        |
  | Watermarks -- Water-marks                                          |
  | workman -- work-woman                                              |
  |                                                                    |
  | The following changes have been made:                              |
  |                                                                    |
  | p. iii "versâ" replaced by "versa"                                 |
  | p.  ix "PRESSE-PÀTE" replaced by "PRESSE-PÂTE"                     |
  | p.  10 "Kulturhistorischen" replaced by "Kulturhistorisches"       |
  |        (caption Fig. 2)                                            |
  | p.  16 "Vollstandige Muhlen" replaced by "Vollständige Mühlen"     |
  | p.  19 "couch-rolls" replaced by "couch rolls"                     |
  | p.  54 "back-fall" replaced by "backfall"                          |
  | p.  57 "Beaume" replaced by "Baumé"                                |
  | p.  84 "tes" replaced by "test"                                    |
  | p. 141 "Beaume" replaced by "Baumé"                                |
  | p. 203 "lignocellulose" replaced by "ligno-cellulose"              |
  | p. 210 "Ubersicht" replaced by "Übersicht"                         |
  | p. 226 "press-pâte" replaced by "presse-pâte"                      |
  | p. 238 "paper makers" replaced by "paper-makers"                   |
  | p. 256 "Andes" replaced by "Andés"                                 |
  | p. 257 "Muller" replaced by "Müller"                               |
  | p. 259 "Hoessle" replaced by "Hössle"                              |
  | p. 260 "Paralatore" replaced by "Parlatore"                        |
  | p. 264 "Muller" replaced by "Müller"                               |
  | p. 267 "Bookbinding" replaced by "Bookmaking"                      |
  | p. 268 "Parish" replaced by "Paris"                                |
  | p. 253 - 272B Further 97 corrections in German, Dutch and French   |
  |        book titles without separate notices.                       |
  |  (4)   "Bye-Products" replaced by "By-Products"                    |
  |  (7)   "evey" replaced by "every"                                  |
  |                                                                    |
  |                                                                    |
  +--------------------------------------------------------------------+





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