Paper pulp

“ These fibres are chiefly used for papers which require strength rather than whiteness of colour, such as wrapping papers, &c.
"Broke" paper is a term applied to paper which has been imperfectly formed on the paper machine or damaged while passing over the drying cylinders. Imperfect sheets when they are not sold as retree, and clean waste paper, also come under this designation and are re-converted into pulp after undergoing the treatment described below. ”

“ Lord Stanhope made several improvements in this, and it is possible that the use of softened paper pulp—flong—for this purpose was his invention. Whether this is true or not, paper was certainly used for stereotyping in France about 1850, and it has been universally used in this important connection ever since.
The paper pulp is hammered on to the type by means of a hard brush, in exactly the same way that antiquaries make impressions from incised rock sculptures. The antiquaries, however, make their casts from the paper moulds in plaster of Paris, but the printer makes his in soft metal. ”

“ The material generally used for this class of paper is poplar chemical fibre and waste paper to the extent of 50 per cent., and even up to 75 and 80 per cent. of the total fibre, the balance being rags, or, in cheaper qualities, sulphite wood pulp; the stuff is all mixed together in large beaters, holding from 800 lbs. up to 1,500 lbs. of pulp, where it is about half beaten, and then finished in one or other form of refining-engine.
"The Americans have, I think, more thoroughly studied the question of super-calendering paper than we, and in this respect get better results and better work. ”

“ 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. ”

“ In such cases the colouring materials are only loosely held, and a portion must therefore be lost in the machine. If added to the pulp before it is sized they become thoroughly mixed with the fibres, and with them enveloped by the size. The pulp should always be coloured before it is sized, except in cases where the alum or resin soap would injure the colours, or be injured by them. While the pulp is being sized and coloured, the finishing touch is given by the engine-man, who examines it and empties it into the stuff-chest. ”

“ The matted pulp, now having sufficient body, passes on between two rolls covered with felt which deliver the web of damp paper upon an endless belt of moist felt, while the "wire" passes under and back to continue a fresh supply. The paper is as yet too fragile to travel alone, and the web felt carries it between two metal rolls called the first press-rolls. These squeeze out more water, give a greater degree of compactness to the fibers, smooth the upper surface, and finally deliver the web of paper to a second felt apron which carries it under and to the back of the second press-rolls. ”

“ 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. ”

“ At the present time this "deckel-edge" paper is being quite extensively used in high-class bookwork. In the case of writing papers, as has already been stated in the description of the beating engines, a vegetable sizing made from resinous matter is introduced into the paper pulp while it is still in solution, and mixes with it thoroughly, thus filling more or less completely the pores of the pulp fibers. ”

“ During the time that the loading, sizing and colouring processes have been going on, the pulp has been continually acted upon by the roll, and if these operations have extended over a considerable time, it is probably in a proper condition for making into paper. The amount of “beating” depends, as has been stated before, upon the nature of the fibre, and also to some extent on the nature of the paper for which it is intended. ”

“ Unbleached wood pulp is the material used, and by prolonged boiling with soda under comparatively low pressure, the fibres receive less drastic chemical treatment than is usual in the preparation of wood pulp. Reduction to fibrous state is accomplished by the edge runner, drawing the fibres out, thus retaining the length and strength. Kraft papers are smooth, light brown in colour, strong and flexible, and are used for wrappings where these qualities are required. ”

“ 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. ”

“ In the manufacture of paper, an article very difficult to rend, and which will, therefore, be found extremely suitable for documents exposed to much tear and wear, as bills of exchange, certificates, also for wrappers, envelopes of all sorts is formed by interposing between two sheets of paper pulp threads of gutta-percha, laid cross-wise like net work, at distances of an inch or two apart, more or less, and combining the two sheets by any suitable machinery as heated rollers. ”

“ The grim old man who may be seen at the upper part of the illustration, with a leg in one page, and with head and body in another, is beating paper stock to a pulp. [2] His only tool is a forked club, with which he pounds on the stone, and macerates the leaves and inner bark of various trees that have been previously saturated in an adjoining tub that is supposed to contain a solution of caustic alkali. How the stock could be reduced to the requisite smoothness for paper pulp by this rough manipulation is a problem that no American paper-maker will undertake to solve. ”

“ To keep the pulp well mixed in the stuff-chest, of which two are usually employed for each machine, a vertical shaft, carrying two horizontal arms, each extending nearly across the interior of the chest, are provided, which are only allowed to revolve at a moderate speed, that is, about two or three revolutions per minute, otherwise the pulp would be liable to work up into knots, and thus form a defective paper. Motion being given to the shaft, the rotating arms keep the pulp and water uniformly mixed, at the same time preventing the pulp from sinking to the bottom of the stuff-chest. ”

“ The tools of the primitive paper-maker consisted of a pulp vat for the fiber-laden water, a frame, or mold, across which was stretched a mesh of closely woven wire, and a removable frame, known as the deckle, which fitted around the edge of the mold to keep the moist pulp from overflowing and to help regulate the thickness of the paper. ”

“ The pulp produced from imperfectly sorted rags has a cloudy appearance, in consequence of some parts being less reduced than others, and the paper made from it is also cloudy or thicker in some parts than in others, as is evident on holding a sheet up before the light. When it is necessary to mix different qualities of rags together to produce different qualities of paper, the rags should be ground separately, and the various pulps mixed together afterwards. ”

“ Mechanical wood pulp which enters so largely into the manufacture of paper is easily recognised by those who have given a fair amount of attention to the microscopical examination of plant life. Wood pulp is always used in conjunction with some binding material such as cotton or flax fibres. Many different kinds of wood are converted into pulp and of course it requires a considerable amount of experience to say exactly what kind of wood has been used in a certain paper. ”

“ A few drops of this mixture dropped upon a small sample of the pulp will indicate if any chlorine be present by the spot assuming a blue colour; if such be not the case, the pulp may be considered free from chlorine.
During the beating, the roll, which should make not less than 220 revolutions per minute, is lowered, a little at a time, so that the cutting edges of the bars and plate may be brought together gradually and equally until the pulp is reduced to the desired condition. The pulp is made long or short according to the quality of paper to be produced ”

“ Within this brief space of time, and the short distance of thirty or forty feet, a continuous stream of fluid pulp is made into paper, dried, polished, and cut up into separate sheets ready for use. The paper thus produced is moderate in price, and, for a large number of purposes, superior in quality to that which was formerly made by hand. In fact, the machine-made papers can be produced of unlimited dimensions; they are of uniform thickness; they can be fabricated at any season of the year ”

“ Transfer or carbon papers so much used in making several copies of an article on the typewriter are made by coating paper with starch, flour, gum, and coloring matter. Paper can be used for shoes and hats, ties, collars, and even for "rubbers." It has been successfully used for sails for light vessels, and is excellent made into light garments for hospital use because it is so cheap that it can be burned after wearing. Wood pulp can be run through fine tubes into water and made so pliable that it can be twisted into cord or spun and woven into "silk." ”

“ Two kinds of wood-pulp are used for paper manufacture, one prepared mechanically and the other chemically. The former is obtained by disintegrating the wood entirely by machinery without the use of chemicals, and is, as may readily be understood, a very inferior pulp. In the manufacture of chemical wood-pulp, very great advances have been made since 1880, and wood-pulp has grown to be one of the most important fibres for paper-making purposes. ”

“ Rude as this process may seem, it is, in its more important features, excepting that of pulp-beating, the process that was used in Europe until the invention of the cylinder and Fourdrinier paper-making machines. Nor is this process entirely out of fashion. There are paper-makers yet living who have p137 taken pulp out of the vats with hand moulds and deckle, and have couched it on felts, substantially by the same method that was in use in Asia fifteen hundred years ago.
Oriental paper-makers do not use rags nor raw cotton for making their pulp. ”

“ The largest paper now made by hand, which is termed Antiquarian, measures 53 inches by 31, and so great is the weight of liquid pulp employed in the formation of a single sheet, that no [41] fewer than nine men are required, besides additional assistance in raising the mould out of the vat by means of pulleys; while by the aid of the paper machine, the most perfect production may be ensured, of a continuous length, and eight feet wide, without any positive necessity for personal superintendence. ”

“ Strange, almost phenomenal, conditions come about in the transformation from filmy pulp to finished paper. A sheet which, though formed, is at the first press-roll too fragile to carry its own weight, becomes possessed of a final strength and power that is almost incredible. The myriad of minute fibers composing the sheet, upon drying uniformly, possesses great aggregate strength. A77 sheet of paper yields readily to tearing, but the same sheet, when a perfectly even tension is applied, will demonstrate that it is possessed of wonderful resisting power. ”

“ Paper which is free from mechanical wood pulp is sometimes referred to as "free."
The strongest and best papers are made from cotton or linen rag fibres. Linen is made from the fibres of the flax. In the raw state the fibres are from 1 inch to 11/2 inches in length, and less than 1/1000 of an inch in diameter. Examined microscopically the fibres appear to be smooth, cylindrical, with markings like the joints of a cane, slight cross markings, and a very fine channel running through the fibres. Papers made from linen are close, strong, and durable. ”

“ The paper thus sized becomes much harder and stronger, by reason of the freedom with which the sheets can contract in drying; and this is mainly the reason why paper made by hand continues to be so much tougher than that made by the machine, in consequence of the natural tendency of the pulp to contract in drying, and consequently becoming, where no resistance is offered, more entwined or entangled, which of course adds very considerably to the strength and durability of the paper. In making by the machine, this tendency, you will observe, is completely checked. ”

“ Hard stock, it is now said, must be used in larger proportions than is required for other descriptions of paper, and that the pulp must be subjected for a greater length of time to the long-beating process, so that the fibre shall be not only long but fine, in order that the paper may be strong, smooth, and even, and that the fibre shall become bedded in the thickness of the paper so as not to mar the surface. ”

“ 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. ”