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

Alexander Watt

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

EAN 8596547015758

DigiCat, 2022

Contact: [email protected]

Table of Contents

PREFACE.

CHAPTER I.

CHAPTER II.

CHAPTER III.

CHAPTER IV.

CHAPTER V.

CHAPTER VI.

CHAPTER VII.

CHAPTER VIII.

CHAPTER IX.

CHAPTER X.

CHAPTER XI.

CHAPTER XII.

CHAPTER XIII.

CHAPTER XIV.

CHAPTER XV.

CHAPTER XVI.

CHAPTER XVII.

CHAPTER XVIII.

CHAPTER XIX.

CHAPTER XX.

TABLES.

List of Works relating to Paper Manufacture.

INDEX.

PREFACE.

Table of Contents

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.

CHAPTER I.

Table of Contents

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.

CHAPTER II.

Table of Contents

MATERIALS USED IN PAPER-MAKING.

Raw Materials.—Rags.—Disinfecting Machine.—Straw.—Esparto Grass.—Wood.—Bamboo.—Paper Mulberry.

In former days the only materials employed for the manufacture of paper were linen and cotton rags, flax and hemp waste, and some few other fibre-yielding materials. The reduction of the excise duty, however, from 3d. to 1½d. per lb., which took effect in the first year of Her Majesty's reign—namely, in 1837—created a greatly increased demand for paper, and caused much anxiety amongst manufacturers lest the supply of rags should prove inadequate to their requirements. Again, in the year 1861 the excise duty was totally abolished, from which period an enormously increased demand for paper, and consequently paper material, was created by the establishment of a vast number of daily and weekly papers and journals in all parts of the kingdom, besides reprints of standard and other works in a cheap form, the copyright of which had expired. It is not too much to say, that unless other materials than those employed before the repeal of the paper duty had been discovered, the abolition of the impost would have proved but of little service to the public at large. Beneficent Nature, however, has gradually, but surely and amply, supplied our needs through the instrumentality of man's restless activity and perseverance.

The following list comprises many of the substances from which cellulose, or vegetable fibre, can be separated for the purposes of paper-making with advantage; but the vegetable kingdom furnishes in addition a vast number of plants and vegetables which may also be used with the same object. We have seen voluminous lists of fibre-yielding materials which have been suggested as suitable for paper-making, but since the greater portion of them are never likely to be applied to such a purpose, we consider the time wasted in proposing them. It is true that the stalks of the cabbage tribe, for example, would be available for the sake of their fibre, but we should imagine that no grower of ordinary intelligence would deprive his ground of the nourishment such waste is capable of returning to the soil, by its employment as manure, to furnish a material for paper-making. Again, we have seen blackberries, and even the pollen (!) of plants included in a list of paper materials, but fortunately the manufacturer is never likely to be reduced to such extremities as to be compelled to use materials of this nature.

Raw Materials.

Cotton rags.

Cotton wool.

Cotton waste.

Cotton-seed waste.

Linen rags.

Linen waste.

Hemp waste.

Manilla hemp.

Flax waste, etc.

Jute waste, etc.

China grass.

Bamboo cane.

Rattan cane.

Banana fibre.

Straw of wheat, etc.

Rushes of various kinds.

New Zealand flax.

Maize stems, husks, etc.

Esparto grass.

Reeds.

Woods of various kinds, especially white non-resinous woods, as poplar, willow, etc.

Wood shavings, sawdust, and chips.

Old netting.

Sailcloth.

Sea grass (Zostera marina).

Fibrous waste resulting from pharmaceutical preparations.

Potato stalks.

Stable manure.

Barks of various trees, especially of the paper mulberry.

Peat.

Twigs of common broom and heather.

Mustard stems after threshing.

Buckwheat straw.

Tobacco stalks.

Beetroot refuse from sugar works.

Megass, or cane trash—refuse of the sugar cane after the juice has been extracted.

Fern leaves.

Tan waste.

Dyers' wood waste.

Old bagging.

Old bast matting.

Hop-bines.

Bean stalks.

Old canvas.

Old rope.

Gunny bags.

Waste paper.

Binders' clippings, etc.

Silk cocoon waste.

Oakum.

Flax tow.

Rag bagging.

Leather waste.

Tarpaulin. Etc., etc.

Rags.—Linen and cotton rags are imported into Great Britain from almost all the countries of Europe, and even from the distant states of South America, British South Africa, and Australasia. The greater proportion, however, come from Germany. The rags collected in England chiefly pass through the hands of wholesale merchants established in London, Liverpool, Manchester, and Bristol, and these are sorted to a certain extent before they are sent to the paper-mills. By this rough sorting, which does not include either cleansing or disinfecting, certain kinds of rags which would be useless to the paper-maker are separated and sold as manure. Woollen rags are not usually mixed with cotton rags, but are generally kept apart to be converted into shoddy. The importance of disinfecting rags before they pass through the hands of the workpeople employed at the paper-mills cannot be over-estimated, and it is the duty of every Government to see that this is effectually carried out, not only at such times when cholera and other epidemics are known to be rife in certain countries from which rags may be imported, but at all times, since there is no greater source of danger to the health of communities than in the diffusion of old linen and cotton garments, or pieces, which are largely contributed by the dwellers in the slums of crowded cities.

Respecting the disinfecting of rags, Davis[11] thus explains the precautions taken in the United States to guard against the dangers of infection from rags coming from foreign or other sources. When cholera, or other infectious or contagious diseases exist in foreign countries, or in portions of the United States, the health officers in charge of the various quarantines in this country require that rags from countries and districts in which such diseases are prevalent shall be thoroughly disinfected before they are allowed to pass their stations. Rags shipped to London, Hull, Liverpool, Italian, or other ports, and re-shipped from such ports to the United States, are usually subjected to the same rule as if shipped direct from the ports of the country in which such diseases prevail. It is usually requisite that the disinfection shall be made at the storehouse in the port of shipment, by boiling the rags several hours under a proper degree of pressure, or in a tightly-closed vessel, or disinfected with sulphurous acid, which is evolved by burning at least two pounds of roll sulphur to every ten cubic feet of room space, the apartment being kept closed for several hours after the rags are thus treated. Disinfection by boiling the rags is usually considered to be the best method. In the case of rags imported from India, Egypt, Spain, and other foreign countries where cholera is liable to become epidemic, it is especially desirable that some efficient, rapid, and thorough process of disinfecting should be devised. In order to meet the quarantine requirements, it must be thorough and certain in its action, and in order that the lives of the workmen and of others in the vicinity may not be endangered by the liberating of active disease-germs, or exposure of decaying and deleterious matters, and that the delay, trouble, and exposure of unbaling and rebaling may be avoided, it must be capable of use upon the rags while in the bale, and of doing its work rapidly when so used.

Disinfecting Machine.—To facilitate the disinfecting of rags while in the bale, Messrs. Parker and Blackman devised a machine, for which they obtained a patent in 1884, from which the following abstract is taken.

Formerly rags and other fibrous materials were disinfected by being subjected to germ-destroying gases or liquids in enclosed chambers, but in order to render the disinfecting process effectual, it was found necessary to treat the material in a loose or separated state, no successful method having been adopted for disinfecting the materials while in the bale. This unbaling and loosening or spreading of the undisinfected material is absolutely unsafe and dangerous to the workmen, or to those in the vicinity, because of the consequent setting free of the disease germs, and the exposing of any decaying or deleterious matters which may be held in the material while it is compressed in the bale. The unbaling and necessary rebaling of the material for transportation also involves much trouble and expense and loss of time. Large and cumbrous apparatus is also necessary to treat large quantities of material loosened or opened out as heretofore.

Fig. 1.

It is specially necessary that rags coming from Egypt and other foreign countries should be thoroughly disinfected by some rapid and effectual means, which, while not endangering the health of workmen employed in this somewhat hazardous task, will fully meet all quarantine requirements. The apparatus devised by Messrs. Parker and Blackman,[12] an abridged description of which is given below, will probably accomplish this much-desired object.

Fig. 2.

In the illustration, Fig. 1, A is the disinfecting chamber. At one end is an opening A¹, and a door B, hinged at its lower edge and adapted to be swung up, so as to close the opening tightly. For supporting and carrying the bale C of material to be placed in the chamber is a carriage C¹, consisting of a platform supported upon wheels or castors c c. While the carriage is wholly within the chamber A, as shown in Fig. 2, these wheels rest upon the false bottom B²; when the carriage is rolled back and out of the chamber, as shown in Fig. 1, they roll upon the upper face of door B swung down. The carriage is provided with a clamping device D to hold the bale firmly and immovably. To cause the carriage to move into and out of the chamber, the inventors provide upon the under side of the platform a fixed sleeve E, interiorly threaded to fit the screw E¹, journalled at one end near the opening in the chamber end in a stationary block E² fixed upon the false bottom B². From this end the screw extends along under the carriage through the screw sleeve and to the other end of the chamber. A collar e² on the screw bears against the inner end of this journal-bearing, and upon the end of the shank e bearing against the other end of the journal is fixed a pinion F, which is to be driven in either direction as desired. Above this journal-bearing is a series of similar bearings (five being shown), G G, passing through the wall of the chamber. Of these the middle one is in a line with the centre of the bale, supported and held on the carriage. The others are arranged at the corners of a square. Journalled in these bearings are the hollow shanks H H of the hollow screws I I pointed at I¹ I¹. Each screw is perforated, i i, between the threads i¹ i¹ from the fixed collar K K. Upon the tubular shanks H H of the screws are fixed the gear-wheels L L. At a short distance from the end of the chamber, A is the hollow chamber or receptacle M, into which is to be forced the disinfectant liquid or gas. The tubular shanks H H of the screws project through the wall M, passing through stuffing-boxes m m, and their bores communicate with the interior of the chamber, the shank of the middle screw being continued through the opposite wall and a stuffing-box, its solid or projecting end being provided with two fixed pulleys, N N, and a loose pulley O. When a gaseous disinfectant is used, it can be forced by any desired means through the pipe S into the chamber. Where a liquid disinfectant is used, an elevated tank R containing the fluid may be used. As most fibrous materials, and especially rags, are baled so as to be in layers, it is preferable so to place the bale upon the carriage that the perforated screws may penetrate the material at right angles to the layers by which the gas or liquid issuing through the holes in the screws passes in all directions throughout the mass within the bale.

In the upper part of chamber A are perforated shelves V V, upon which, if desired, the material can be spread out and subjected to disinfecting gas or vapour. On the top of the chamber is a tank W nearly filled with disinfecting liquid. A passage W¹ extends from upper part of the chamber up into the tank above the level of the liquid therein, and is then carried at its end down below the surface of the liquid. At its other end the tank is provided at its top with a discharge opening X and a suitable pipe X¹, forming a continuation of the opening; by this means all foul and deleterious vapours or gases passing out of the closed chamber A through the passage W must pass through the disinfecting liquid in the tank before escaping through the opening X and stack X¹ into the air, and are thus rendered harmless.

When a sufficient amount of the disinfectant has been forced into and through the bale, the disinfectant is turned off, and cold dry air can be forced through chamber M, and out through the nozzles and bale, whereby the material within the bale becomes cooled and dried, and all the foul air from the chamber A driven out, so that it may be opened and entered with safety. Any suitable disinfectant may be used with this apparatus, as, for example, sulphurous acid, in gas or solution, superheated steam, carbolic acid, or any solution or vapour containing chlorine.

Straw.—Very large quantities of this material are used in the manufacture of paper, but more especially for newspapers, the straw from wheat and oats being mostly employed. Although the percentage of cellulose in straw is about equal to that of esparto, the severe treatment it requires to effectually remove the silicious coating by which the fibre is protected, and to render the knots amenable to the action of the bleach, greatly reduces the yield of finished pulp. Many processes have been introduced for the treatment of straw for paper-making, but the most successful of them appear to be modifications of a process introduced in 1853 by MM. Coupier and Mellier.

Esparto Grass.—This important fibrous material is largely imported from Algeria, Spain, and other countries, and constitutes one of the most valuable fibre-yielding materials with which the manufacturer has to deal. Some idea of the amount of esparto and other fibres which find their way to our shores may be gleaned from the fact that while the import of cotton and linen rags in the year 1884 was 36,233 tons, of the value of £487,866, that of esparto and other fibres amounted to 184,005 tons, of the value of £1,125,553.

Wood.—As a paper-making material, the fibre obtained from various kinds of wood now holds an important position, since the sources of supply are practically inexhaustible. The first practical process for manufacturing pulp from wood fibre was perfected and introduced by the author's father, the late Mr. Charles Watt, who, in conjunction with Mr. H. Burgess, obtained a patent for the invention on August 19th, 1853. The process was afterwards publicly exhibited at a small works on the Regent's Canal, when the Earl of Derby (then Lord Stanley), many scientific men and representatives of the press, were present, and expressed themselves well satisfied with its success. Specimens of the wood paper, including a copy of the Weekly Times printed thereon, were exhibited, as also some water-colour drawings which had been produced upon paper made from wood pulp. Failing to get the process taken up in England, an American patent was applied for and obtained in 1854, which was subsequently purchased; but with the exception of an instalment, the purchase-money was never paid to the inventor! Thus the process got into other hands, the original inventor alone being unbenefited by it.

It has been repeatedly stated,[13] no doubt unwittingly, that a person named Houghton first introduced the wood paper process into this country; but considering that his patent was not obtained until 1857, or four years after the process above referred to was patented and publicly exhibited in England, it will be seen that the statement is absolutely without foundation. The first knowledge Mr. Houghton received concerning wood as a paper-making material was from the author's father, and he (Mr. Houghton), in conjunction with Mr. Burgess, introduced the Watt and Burgess process into America in the year 1854. These are the facts.

Bamboo (Bambusa vulgaris).—The leaves and fresh-cut stems of this plant are used for paper material, but require to pass through a preliminary process of crushing, which is effected by suitable rolls, the second series of crushing rolls being grooved or channelled to split or divide the material, after which the stems are cut to suitable lengths for boiling.

Paper Mulberry (Broussonetia papyrifera).—The inner bark of this tree, and also some other basts, have long been used by the Japanese and Chinese in the manufacture of paper of great strength, but of extreme delicacy.

CHAPTER III.

Table of Contents

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.

Preliminary Operations.—Before the rags are submitted to the various processes which constitute the art of paper-making, they are subjected to certain preliminary operations to free them from dirty matters, dust, and even sand, which is sometimes fraudulently introduced into rags to increase their weight. This preliminary treatment may be classified under the following heads, namely:—Sorting; Cutting; Willowing; Dusting.

Sorting.—The rags being removed from the bags or bales in which they are packed, require first to be sorted according to the nature and quality of the fabrics of which they are composed; thus linen, cotton, hemp, wool, &c., must be carefully separated from each other; the thickness of the substance, its condition as to the wear it