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Transcriber's note:
Text enclosed by underscores is in italics (_italics_).
Text enclosed by equal signs is in bold face (=bold=).
Text enclosed by double plus signs is underlined
(++underlined++).
The 3-star asterism symbol is denoted by ***.
The right-pointing finger symbol is denoted by ==>.
A carat character is used to denote superscription. A
single character following the carat is superscripted
(examples: B^2, A^4).
Basic fractions are displayed as ½ ⅓ ¼ etc; other fractions
are shown in the form a/b, for example 7/16 or 1/125.
Some minor changes are noted at the end of the book.
THE ART OF PAPER-MAKING
* * * * * *
_WORKS BY THE SAME AUTHOR._
Just ready. Fourth Edition, Revised and Enlarged. Crown 8vo,
7s. 6d. cloth.
THE ART OF SOAP-MAKING: A Practical Handbook of the Manufacture
of Hard and Soft Soaps, Toilet Soaps, &c. Including many New
Processes, and a Chapter on the Recovery of Glycerine from Waste
Leys. With numerous Illustrations.
"Really an excellent example of a technical manual, entering as
it does, thoroughly and exhaustively, both into the theory and
practice of soap manufacture. The book is well and honestly done,
and deserves the considerable circulation with which it will
doubtless meet."--_Knowledge._
Second Edition. Crown 8vo, 9s. cloth.
THE ART OF LEATHER MANUFACTURE: Being a Practical Handbook, in
which the Operations of Tanning, Currying, and Leather Dressing
are fully Described, and the Principles of Tanning Explained, and
many Recent Processes Introduced. With numerous Illustrations.
"A sound, comprehensive treatise on tanning and its accessories....
The book is an eminently valuable production."--_Chemical Review._
Just Published. Third Edition, revised and much enlarged. 600 pp.,
crown 8vo, 9s. cloth.
ELECTRO-DEPOSITION: A Practical Treatise on the Electrolysis of
Gold, Silver, Copper, Nickel, and other Metals and Alloys. With
descriptions of Voltaic Batteries, Magneto and Dynamo-Electric
Machines, Thermopiles, and of the Materials and Processes
used in every Department of the Art, and several Chapters on
ELECTRO-METALLURGY. With numerous Illustrations.
"Eminently a book for the practical worker in electro-deposition.
It contains minute and practical descriptions of methods, processes
and materials, as actually pursued and used in the workshop.
Mr. Watt's book recommends itself to all interested in its
subjects."--_Engineer._
Just Published. Ninth Edition, enlarged and revised, 12mo, 4s. cloth.
ELECTRO-METALLURGY: Practically Treated. Ninth Edition, Enlarged
and Revised, with Additional Matter and Illustrations, including
the most recent Processes.
"From this book both amateur and artisan may learn
everything necessary for the successful prosecution of
electro-plating."--_Iron._
CROSBY LOCKWOOD & SON, 7, Stationers' Hall Court, London, E.C.
* * * * * *
THE ART OF PAPER-MAKING
A Practical Handbook of the Manufacture
of Paper from Rags, Esparto, Straw, and
Other Fibrous Materials, Including
the Manufacture of Pulp from
Wood Fibre
With a Description of the Machinery and Appliances used
To Which Are Added
Details of Processes for Recovering Soda from
Waste Liquors
by
ALEXANDER WATT
Author of "The Art of Soap-Making," "Leather Manufacture,"
"Electro-Metallurgy," "Electro-Deposition," etc., etc.
[Illustration: Capio Lumen (Publisher's colophon)]
London
Crosby Lockwood and Son
7, Stationers' Hall Court, Ludgate Hill
1890
[All rights reserved]
London:
Printed By J. S. Virtue and Co., Limited.
City Road.
PREFACE.
In the present volume, while describing the various operations
involved in the manufacture of paper, the Author has endeavoured to
render the work serviceable as a book of reference in respect to
the processes and improvements which have from time to time been
introduced, and many of which have been more or less practically
applied either at home or abroad.
The recovery of soda from waste liquors has been fully dealt with,
and the details of several applied processes explained.
Special attention has also been directed to some of the more
important methods of producing pulp from wood fibre, since it
is highly probable that from this inexhaustible source the
paper-maker will ultimately derive much of the cellulose used in
his manufacture. Indeed it may be deemed equally probable, when
the processes for disintegrating wood fibre, so largely applied
in America and on the Continent, become better understood in this
country, that their adoption here will become more extensive than
has hitherto been the case.
To render the work more readily understood alike by the practical
operator and the student, care has been taken to avoid, as far as
possible, the introduction of unexplained technicalities; at the
same time it has been the writer's aim to furnish the reader with a
variety of information which, it is hoped, will prove both useful
and instructive.
It is with much pleasure that the Author tenders his sincere thanks
to Mr. Sydney Spalding, of the Horton Kirby Mills, South Darenth,
for his kind courtesy in conducting him through the various
departments of the mill, and for explaining to him the operations
performed therein. To Mr. Frank Lloyd he also acknowledges his
indebtedness for the generous readiness with which he accompanied
him over the _Daily Chronicle_ Mill at Sittingbourne, and for
the pains he took to supply information as to certain details
at the Author's request. His best thanks are also due to those
manufacturers of paper-making machinery who supplied him with many
of the blocks which illustrate the pages of the book.
BALHAM, SURREY, _January, 1890_.
CONTENTS.
CHAPTER I.
_CELLULOSE._
PAGE
Cellulose--Action of Acids on Cellulose--Physical Characteristics
of Cellulose--Micrographic Examination of Vegetable Fibres--
Determination of Cellulose--Recognition of Vegetable Fibres by
the Microscope 1
CHAPTER II.
_MATERIALS USED IN PAPER-MAKING._
Raw Materials--Rags--Disinfecting Machine--Straw--Esparto Grass--
Wood--Bamboo--Paper Mulberry 9
CHAPTER III.
_TREATMENT OF RAGS._
Preliminary Operations--Sorting--Cutting--Bertrams' Rag-cutting
Machine--Nuttall's Rag-cutter--Willowing--Bertrams' Willow
and Duster--Dusting--Bryan Donkin's Duster or Willow--Donkin's
Devil 19
CHAPTER IV.
_TREATMENT OF RAGS_ (_continued_).
Boiling Rags--Bertrams' Rag-boiler--Donkin's Rag-boiler--Washing
and Breaking--Bertrams' Rag-engine--Bentley and Jackson's
Rag-engine--Draining--Terrance's Drainer 29
CHAPTER V.
_TREATMENT OF ESPARTO._
Preliminary Treatment--Picking--Willowing Esparto--Boiling
Esparto--Sinclair's Esparto Boiler--Roeckner's Boiler--Mallary's
Process--Carbonell's Process--Washing Boiled Esparto--Young's
Process--Bleaching the Esparto 40
CHAPTER VI.
_TREATMENT OF WOOD._
I. CHEMICAL PROCESSES--Watt and Burgess's Process--Sinclair's
Process--Keegan's Process--American Wood-pulp System--Aussedat's
Process--Acid Treatment of Wood--Pictet and Brélaz's Process--
Barre and Blondel's Process--Poncharac's Process--Young and
Pettigrew's Process--Fridet and Matussière's Process 53
CHAPTER VII.
_TREATMENT OF WOOD_ (_continued_).
Sulphite Processes--Francke's Process--Ekman's Process--Dr.
Mitscherlich's Process--Ritter and Kellner's Boiler--
Partington's Process--Blitz's Process--M'Dougall's Boiler for
Acid Processes--Graham's Process--Objections to the Acid or
Sulphite Processes--Sulphite Fibre and Resin--Adamson's
Process--Sulphide. Processes--II. MECHANICAL PROCESSES--
Voelter's Process for preparing Wood-pulp--Thune's Process 68
CHAPTER VIII.
_TREATMENT OF VARIOUS FIBRES._
Treatment of Straw--Bentley and Jackson's Boiler--Boiling the
Straw--Bertrams' Edge-runner--M. A. C. Mellier's Process--
Manilla, Jute, &c.--Waste Paper--Boiling Waste Paper--Ryan's
Process for Treating Waste Paper 80
CHAPTER IX.
_BLEACHING._
Bleaching Operations--Sour Bleaching--Bleaching with Chloride
of Lime--Donkin's Bleach Mixer--Bleaching with Chlorine Gas
(Glaser's Process)--Electrolytic Bleaching (C. Watt's Process)--
Hermite's Process--Andreoli's Process--Thompson's Process--
Lunge's Process--Zinc Bleach Liquor--Alum Bleach Liquor--New
Method of Bleaching 89
CHAPTER X.
_BEATING OR REFINING._
Beating--Mr. Dunbar's Observations on Beating--Mr. Arnot on
Beating Engines--Mr. Wyatt on American Refining Engines--The
Beating Engine--Forbes' Beating Engine--Umpherston's Beating
Engine--Operation of Beating--Test for Chlorine--Blending 101
CHAPTER XI.
_LOADING.--SIZING.--COLOURING._
Loading--Sizing--French Method of preparing Engine Size--Zinc
Soaps in Sizing--Colouring--Animal or Tub Sizing--Preparation
of Animal Size--American Method of Sizing--Machine Sizing--
Double-sized Paper--Mr. Wyatt's Remarks on Sizing 114
CHAPTER XII.
_MAKING PAPER BY HAND._
The Vat and Mould--Making the Paper--Sizing and Finishing 129
CHAPTER XIII.
_MAKING PAPER BY MACHINERY._
The Fourdrinier Machine--Bertrams' Large Paper Machine--Stuff
Chests--Strainers--Revolving Strainer and Knotter--
Self-cleansing Strainer--Roeckner's Pulp Strainers--The
Machine Wire and its Accessories--Conical Pulp-Saver--The
Dandy-Roll--Water-Marking--De la Rue's Improvements in
Water-Marks--Suction Boxes--Couch Rolls--Press Rolls--
Drying Cylinders--Smoothing Rolls--Single Cylinder Machines 133
CHAPTER XIV.
_CALENDERING, CUTTING, AND FINISHING._
Web-Glazing--Glazing Calender Damping Rolls--Finishing--Plate
Glazing--Donkin's Glazing Press--Mr. Wyatt on American
Super-Calendering--Mr. Arnot on Finishing--Cutting--Revolving
Knife Cutter--Bertrams' Single-sheet Cutter--Packing the
finished Paper--Sizes of Paper 154
CHAPTER XV.
_COLOURED PAPERS._
Coloured Papers--Colouring Matters used in Paper-making--American
Combinations for Colouring--Mixing Colouring Materials
with Pulp--Colouring Paper for Artificial Flowers--Stains
for Glazed Papers--Stains for Morocco Papers--Stains for
Satin Papers 165
CHAPTER XVI.
_MISCELLANEOUS PAPERS._
Waterproof Paper--Scoffern and Tidcombe's Process--Dr. Wright's
Process for preparing Cupro-Ammonium--Jouglet's Process--
Waterproof Composition for Paper--Toughening Paper--Morfit's
Process--Transparent Paper--Tracing Paper--Varnished Paper--
Oiled Paper--Lithographic Paper--Cork Paper--New Japanese
Paper--Blotting Paper--Parchment Paper--Mill and Cardboard--
Making Paper or Cardboard with two Faces by ordinary
Machine--Test Papers 174
CHAPTER XVII.
_MACHINERY USED IN PAPER-MAKING._
Bentley and Jackson's Drum-Washer--Drying Cylinders--Self-acting
Dry Felt Regulator--Paper Cutting Machine--Single-web
Winding Machine--Cooling and Damping Rolls--Reversing or
Plate-glazing Calender--Plate-planing Machine--Roll-bar
Planing Machine--Washing Cylinder for Rag Engine--Bleach Pump--
Three-roll Smoothing Presses--Back-water Pump--Web-glazing
Calender--Reeling Machine--Web-ripping Machine--Roeckner's
Clarifier--Marshall's Perfecting Engine 184
CHAPTER XVIII.
_RECOVERY OF SODA FROM SPENT LIQUORS._
Recovery of Soda--Evaporating Apparatus--Roeckner's Evaporator--
Porion's Evaporator--Yaryan's Evaporator--American System
of Soda Recovery 204
CHAPTER XIX.
_DETERMINING THE REAL VALUE OR PERCENTAGE
OF COMMERCIAL SODAS, CHLORIDE OF LIME, ETC._
Examination of Commercial Sodas--Mohr's Alkalimeter--Preparation
of the Test Acid--Sampling Alkalies--The Assay--Estimation of
Chlorine in Bleaching Powder--Fresenius' Method--Gay-Lussac's
Method--The Test Liquor--Testing the Sample--Estimation of
Alumina in Alum Cake, &c. 221
CHAPTER XX.
_USEFUL NOTES AND TABLES._
Preparation of Lakes--Brazil-wood Lake--Cochineal Lake--Lac
Lake--Madder Lake--Orange Lake--Yellow Lake--Artificial
Ultramarine--Twaddell's Hydrometer--Imitation Manilla from
Wood-pulp--Testing Ultramarines--Strength of Paper 235
TABLES.--Dalton's Table showing the Proportion of Dry Soda in
Leys of different Densities--Table of Strength of Caustic Soda
Solutions at 59° F. = 150° C. (Tünnerman)--Table showing
the Specific Gravity corresponding with the Degrees of Baumé's
Hydrometer--Table of Boiling Points of Alkaline Leys--Table
showing the Quantity of Caustic Soda in Leys of different
Densities--Table showing the Quantity of Bleaching Liquid
at 6° Twaddell (specific gravity 1·030) required to be added to
Weaker Liquor to raise it to the given Strengths--Comparative
French and English Thermometer Scales--Weights and
Measures of the Metrical System--Table of French Weights
and Measures 241
LIST OF WORKS RELATING TO PAPER MANUFACTURE 246
THE ART OF PAPER-MAKING.
CHAPTER I.
_CELLULOSE._
Cellulose.--Action of Acids on Cellulose.--Physical
Characteristics of Cellulose.--Micrographic Examination of
Vegetable Fibres.--Determination of Cellulose.--Recognition of
Vegetable Fibres by the Microscope.
=Cellulose.=--Vegetable fibre, when deprived of all incrusting or
cementing matters of a resinous or gummy nature, presents to us the
true fibre, or _cellulose_, which constitutes the essential basis
of all manufactured paper. Fine linen and cotton are almost pure
cellulose, from the fact that the associated vegetable substances
have been removed by the treatment the fibres were subjected to in
the process of their manufacture; pure white, unsized, and unloaded
paper may also be considered as pure cellulose from the same cause.
Viewed as a chemical substance, cellulose is white, translucent,
and somewhat heavier than water. It is tasteless, inodorous,
absolutely innutritious, and is insoluble in water, alcohol, and
oils. Dilute acids and alkalies, even when hot, scarcely affect
it. By prolonged boiling in dilute acids, however, cellulose
undergoes a gradual change, being converted into _hydro-cellulose_.
It is also affected by boiling water alone, especially under high
pressure, if boiled for a lengthened period. Without going deeply
into the chemical properties of cellulose, which would be more
interesting to the chemist than to the paper manufacturer, a few
data respecting the action of certain chemical substances upon
cellulose will, it is hoped, be found useful from a practical point
of view, especially at the present day, when so many new methods of
treating vegetable fibres are being introduced.
=Action of Acids on Cellulose.=--When concentrated sulphuric acid
is added very gradually to about half its weight of linen rags
cut into small shreds, or strips of unsized paper, and contained
in a glass vessel, with constant stirring, the fibres gradually
swell up and disappear, without the evolution of any gas, and a
tenacious mucilage is formed which is entirely soluble in water.
If, after a few hours, the mixture be diluted with water, the
acid neutralised with chalk, and after filtration, any excess
of lime thrown down by cautiously adding a solution of oxalic
acid, the liquid yields, after a second filtration and the
addition of alcohol in considerable excess, a gummy mass which
possesses all the characters of _dextrin_. If instead of at once
saturating the diluted acid with chalk, we boil it for four or
five hours, the _dextrin_ is entirely converted into grape sugar
(_glucose_), which, by the addition of chalk and filtration, as
before, and evaporation at a gentle heat to the consistence of
a syrup, will, after repose for a few days, furnish a concrete
mass of crystallised sugar. Cotton, linen, or unsized paper, thus
treated, yield fully their own weight of gum and one-sixth of
their weight of grape sugar. Pure cellulose is readily attacked
by, and soon becomes dissolved in, a solution of oxide of copper
in ammonia (_cuprammonium_), and may again be precipitated in
colourless flakes by the addition of an excess of hydrochloric
acid, and afterwards filtering and washing the precipitate.
Concentrated boiling hydrochloric acid converts cellulose into a
fine powder, without, however, altering its composition, while
strong nitric acid forms nitro-substitution products of various
degrees, according to the strength of the acid employed. "Chlorine
gas passed into water in which cellulose is suspended rapidly
oxidises and destroys it, and the same effect takes place when
hypochlorites, such as hypochlorite of calcium, or bleaching
liquors, are gently treated with it. It is not, therefore, the
cellulose itself which we want the bleaching liquor to operate
upon, but only the colouring matters associated with it, and care
must be taken to secure that the action intended for the extraneous
substances alone does not extend to the fibre itself. Caustic
potash affects but slightly cellulose in the form in which we have
to do it, but in certain less compact conditions these agents
decompose or destroy it."--_Arnot._[1]
=Physical Characteristics of Cellulose.=--"The physical condition
of cellulose," says Mr. Arnot, "after it has been freed from
extraneous matters by boiling, bleaching, and washing, is of great
importance to the manufacturer. Some fibres are short, hard,
and of polished exterior, while others are long, flexible, and
barbed, the former, it is scarcely necessary to say, yielding
but indifferent papers, easily broken and torn, while the papers
produced from the latter class of fibres are possessed of a great
degree of strength and flexibility. Fibres from straw, and from
many varieties of wood, may be taken as representatives of the
former class, those from hemp and flax affording good illustrations
of the latter. There are, of course, between these extremes all
degrees and combinations of the various characteristics indicated.
It will be readily understood that hard, acicular[2] fibres do not
felt well, there being no intertwining or adhesion of the various
particles, and the paper produced is friable. On the other hand,
long, flexible, elastic fibres, even though comparatively smooth
in their exterior, intertwine readily, and felt into a strong
tough sheet.... Cotton fibre is long and tubular, and has this
peculiarity, that when dry the tubes collapse and twist on their
axes, this property greatly assisting the adhesion of the particles
in the process of paper-making. In the process of dyeing cotton,
the colouring matter is absorbed into the tubes, and is, as will
be readily appreciated, difficult of removal therefrom. Papers made
exclusively of cotton fibre are strong and flexible, but have a
certain sponginess about them which papers made from linen do not
possess."
Linen--the cellulose of the flax-plant--before it reaches the hands
of the paper-maker has been subjected to certain processes of
steeping or _retting_, and also subsequent boilings and bleachings,
by which the extraneous matters have been removed, and it therefore
requires but little chemical treatment at his hands. "Linen fibre,"
Arnot further observes, "is like cotton, tubular, but the walls of
the tubes are somewhat thicker, and are jointed or notched like a
cane or rush; the notches assist greatly in the adhesion of the
fibres one to another. This fibre possesses the other valuable
properties of length, strength, and flexibility, and the latter
property is increased when the walls of the tubes are crushed
together under the action of the beating-engine." From this fibre
a very strong, compactly felted paper is made; indeed, no better
material than this can be had for the production of a first-class
paper. Ropes, coarse bags, and suchlike are made from hemp, the
cellulose or fibre of which is not unlike that of flax, only it is
of a stronger, coarser nature. Manilla[3] yields the strongest of
all fibres. Jute, which is the fibre or inside bark of an Indian
plant (_Corchorus capsularis_), yields a strong fibre, but is very
difficult to bleach white. Esparto fibre holds an intermediate
place between the fibres just described and those of wood and
straw.... The fibre of straw is short, pointed, and polished, and
cannot of itself make a strong paper. The nature of wood fibre
depends, as may readily be supposed, upon the nature of the wood
itself. Yellow pine, for example, yields a fibre long, soft, and
flexible, in fact very like cotton; while oak and many other woods
yield short circular fibres which, unless perfectly free from
extraneous matters, possess no flexibility, and in any case are not
elastic.
=Micrographic Examination of Vegetable Fibres.=--The importance
of the microscope in the examination of the various fibres that
are employed in paper manufacture will be readily evident from
the delicate nature of the cellulose to be obtained therefrom.[4]
Amongst others M. Girard has determined, by this method of
examination, the qualities which fibres ought to possess to suit
the requirements of the manufacturer. He states that absolute
length is not of much importance, but that the fibre should be
slender and elastic, and possess the property of turning upon
itself with facility. Tenacity is of but secondary importance, for
when paper is torn the fibres scarcely ever break. The principal
fibres employed in paper-making are divided into the following
classes:--
1. _Round, ribbed fibres_, as hemp and flax.
2. _Smooth_, or _feebly-ribbed fibres_, as esparto, jute,
phormium (New Zealand flax), dwarf palm, hop, and sugar-cane.
3. _Fibro-cellular substances_, as the pulp obtained from the
straw of wheat and rye by the action of caustic ley.
4. _Flat fibres_, as cotton, and those obtained by the action of
caustic ley upon wood.
5. _Imperfect substances_, as the pulp obtained from sawdust.
In this class may also be included the fibre of the so-called
"mechanical wood pulp."
=Determination of Cellulose.= For the determination of cellulose
in wood and other vegetable fibres to be used in paper-making
Müller recommends the following processes:[5] 5 grammes weight
of the finely-divided substance is boiled four or five times in
water, using 100 cubic centimètres[6] each time. The residue is
then dried at 100° C. (212° Fahr.), weighed, and exhausted with
a mixture of equal measures of benzine and strong alcohol, to
remove fat, wax, resin, &c. The residue is again dried and boiled
several times in water, to every 100 c.c. of which 1 c.c. of strong
ammonia has been added. This treatment removes colouring matter and
pectous[7] substances. The residue is further bruised in a mortar
if necessary, and is then treated in a closed bottle with 250 c.c.
of water, and 20 c.c. of bromine water containing 4 c.c. of bromine
to the litre.[8] In the case of the purer bark-fibres, such as flax
and hemp, the yellow colour of the liquid only slowly disappears,
but with straw and woods decolorisation occurs in a few minutes,
and when this takes place more bromine water is added, this being
repeated until the yellow colour remains, and bromine can be
detected in the liquid after twelve hours. The liquid is then
filtered, and the residue washed with water and heated to boiling
with a litre of water containing 5 c.c. of strong ammonia. The
liquid and tissue are usually coloured brown by this treatment. The
undissolved matter is filtered off, washed, and again treated with
bromine water. When the action seems complete the residue is again
heated with ammoniacal water. This second treatment is sufficient
with the purer fibres, but the operation must be repeated as often
as the residue imparts a brownish tint to the alkaline liquid. The
cellulose is thus obtained as a pure white body; it is washed with
water, and then with boiling alcohol, after which it may be dried
at 100° C. (212° Fahr.) and weighed.
=Recognition of Vegetable Fibres by the Microscope.=--From
Mr. Allen's admirable and useful work on "Commercial Organic
Analysis"[9] we make the following extracts, but must refer the
reader to the work named for fuller information upon this important
consideration of the subject. In examining fibres under the
microscope, it is recommended that the tissues should be cut up
with sharp scissors, placed on a glass slide, moistened with water,
and covered with a piece of thin glass. Under these conditions:--
_Filaments of Cotton_ appear as transparent tubes, flattened and
twisted round their axes, and tapering off to a closed point at
each end. A section of the filament somewhat resembles the figure
8, the tube, originally cylindrical, having collapsed most in the
middle, forming semi-tubes on each side, which give the fibre,
when viewed in certain lights, the appearance of a flat ribbon,
with the hem of the border at each edge. The twisted, or corkscrew
form of the dried filament of cotton distinguishes it from all
other vegetable fibres, and is characteristic of the matured pod,
M. Bauer having found that the fibres of the unripe seed are
simply untwisted cylindrical tubes, which never twist afterwards
if separated from the plant. The matured fibres always collapse
in the middle as described, and undergo no change in this respect
when passing through all the various operations to which cotton is
subject, from spinning to its conversion into pulp for paper-making.
_Linen_, _or Flax Fibre_, under the microscope, appears as hollow
tubes, open at both ends, the fibres being smooth, and the inner
tube very narrow, and joints, or _septa_,[10] appear at intervals,
but are not furnished with hairy appendages as is the case with
hemp. When flax fibre is immersed in a boiling solution of equal
parts of caustic potash and water for about a minute, then removed
and pressed between folds of filter-paper, it assumes a dark yellow
colour, whilst cotton under the same treatment remains white or
becomes very bright yellow. When flax, or a tissue made from it,
is immersed in oil, and then well pressed to remove excess of
the liquid, it remains translucent, while cotton, under the same
conditions, becomes opaque.
_New Zealand Flax_ (_Phormium tenax_) may be distinguished from
ordinary flax or hemp by a reddish colour produced on immersing
it first in a strong chlorine water, and then in ammonia. In
machine-dressed New Zealand flax the bundles are translucent and
irregularly covered with tissue; spiral fibres can be detected in
the bundles, but less numerous than in Sizal. In Maori-prepared
phormium the bundles are almost wholly free from tissue, while
there are no spiral fibres.
_Hemp Fibre_ resembles flax, and exhibits small hairy appendages at
the joints. In Manilla hemp the bundles are oval, nearly opaque,
and surrounded by a considerable quantity of dried-up cellular
tissue composed of rectangular cells. The bundles are smooth, very
few detached ultimate fibres are seen, and no spiral tissue.
_Sizal_, _or Sisal Hemp_ (_Agave Americana_), forms oval fibrous
bundles surrounded by cellular tissue, a few smooth ultimate fibres
projecting from the bundles; is more translucent than Manilla, and
a large quantity of spiral fibres are mixed up in the bundles.
_Jute Fibre_ appears under the microscope as bundles of tendrils,
each being a cylinder, with irregular thickened walls. The
bundles offer a smooth cylindrical surface, to which the silky
lustre of jute is due, and which is much increased by bleaching.
By the action of hypochlorite of soda the bundles of fibres
can be disintegrated, so that the single fibres can be readily
distinguished under the microscope. Jute is coloured a deeper
yellow by sulphate of aniline than is any other fibre.