Pulp

“ Pulp, pulp, n. the soft fleshy part of bodies, e.g. of teeth: marrow: the soft part of plants, esp. of fruits: any soft mass: the soft mass obtained from the breaking and grinding of rags, &c., before it is hardened into paper.—v.t. to reduce to pulp: to deprive of pulp: to separate the pulp.—v.i. to become ripe or juicy, like the pulp of fruit.—ns. Pulp′-en′gine, a machine for converting rags, &c., into pulp; Pulp′ifier, an apparatus for reducing fresh meat to a jelly-like pulp, to aid digestion.—v.t. Pulp′ify, to make into pulp. ”

“ The pulp, diluted with a large volume of water, consists of innumerable fibres, their length being at least 100 times their diameter, and as is the case of all water-borne bodies travelling in a fast stream, they take up the position in which their length is parallel to the direction of flow. ”

“ Mechanical wood pulp is made up of little pieces of wood with all the resins and other impurities of the original wood, and when examined carefully, the fragments of wood can be seen, and the splinters appear to be held together by the plant cells. Mechanical wood pulp possesses very little felting quality, and requires the addition of larger fibres, such as chemical wood, in order to make paper successfully. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ A quality of pulp intermediate between chemically produced wood cellulose and ground wood is obtained by bleaching an especially finely ground quality of pulp wood. This product is excellent as a filler for medium grades of paper, as it is opaque—fine, and of fair color. ”

“ In order to keep the pulp properly agitated in the mould vat, a segment frame, having rails extended across the vat, is moved to and fro; as the drum mould goes round, the fibres of the pulp are forced against its circumference, and as the water passes through, the fibres adhere, forming the sheet of paper, which, on arriving at a couching roller above, is taken up as usual by an endless felt, conducted away to the drying apparatus, and thence to the reel to be wound up. ”

“ The object being merely to dry the pulp, a very heavy web can be obtained, since the water leaves this pulp very freely. The wood pulp thus obtained is perfectly clean, of a soft, white spongy fibre, and a greater portion of it is mixed with a small proportion of rag pulp and worked into book and fine printing papers. Sometimes the wood pulp is used alone or mixed with white paper shavings for book paper. The fibres are rather deficient in strength, but as a material for blotting paper they are said to be unsurpassed, while the wood paper is much liked by printers. ”

“ There is at present a large demand for paper pulp in America, Europe, and Japan. According to authorities on the subject, the spruce wood, which forms at least two-thirds of all the woods converted into pulp, is being exhausted. ”

“ I do not hesitate to destroy pulps to-day, because we have such an excellent knowledge of the structure of the tooth, and we now know that simply because the pulp is lost we must not suppose the tooth to be entirely dead, but there is still life from the membranes of the root. So I am now inclined to cap only those pulps which present the best conditions for capping. If a pulp presents any symptoms of congestion or inflammation, I believe you had better dispatch it at once, in order to give the best results to the patient, but I am not a believer in the wholesale destroying of pulps. ”

“ Chemical wood pulp of the best quality makes an excellent product, and is largely used for both print and book paper; it is frequently mixed with rag pulp, making a paper that can scarcely be distinguished from that made entirely from fine rags, though it is not of the proper firmness for the best flat or writing papers. All ordinary newspapers, as well as some of the cheaper grades of book and wrapping paper, are made entirely from wood, the sulphite or soda process supplying the fiber, and ground wood being used as a filler. ”

“ 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. ”

“ In delicate relief-work, a pulp is prepared of scrap paper, which is dried, then ground to powder and mixed with paste and a proportion of potash until a very fine, thin paste is formed. Papier-maché is an exceedingly strong, tough, durable substance, slightly elastic, and not liable to warp or fracture. ”

“ The metal of the can has a bleaching action on the pulp and this is greatly increased if the pulp is stacked hot or stored in a hot warehouse. If stacked while excessively hot, stack-burning may occur with consequent darkening of the pulp. ”

“ 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. ”

“ 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:—
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. ”

“ The steps subsequent to cooking chemical pulps of all kinds are similar. After emptying the digesters, the soft, discolored mass of fibers is washed and bleached. The yield of cellulose fiber is close to fifty per cent of the air-dry weight of the wood. The shives and undigested particles are removed by screening, and the pulp is either run out like ground wood on wet machines, or made up into rolls, or 36sheets, on a paper-machine. The soda pulp is shipped in rolls and the sulphite in sheets, as this is the most favorable form in which to handle them at the paper-mill. ”

“ The water thus heated and forced in leaves the wood or the pulp in the most desirable condition for work and for colour. Pulp made from wood treated below the boiling point will be white; but this process is said to secure the desired manilla colour by raising the temperature to 240° or 250° for a light pulp, and as high as 280° for a dark pulp. No pressure is required from the steam above three atmospheres, but the press may give from 450 to 500 lbs. to the square inch, and practice has shown that the greater the pressure the more speedy is the operation on the wood. ”

“ From 3 to 4 lbs. of the mixture of resin soap and starch paste to each 100 lbs. of dry pulp are about the proportions in which the size is generally used, but the quantity added to the pulp in the beater depends upon whether the paper is to be soft-sized or hard-sized.
Sizing is chiefly applied to papers which are to be written [118] upon with ordinary inks, and also, with a few exceptions, to printing papers, the object being to close the pores of the paper and render it non-absorbent, by which the spreading or running of the ink is effectually prevented. ”

“ 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. ”

“ There is ample time to determine the specific gravity of the sample of partly concentrated pulp and from its volume as obtained by the gage glass to calculate the volume to which the pulp should be evaporated to secure the desired specific gravity in the finished product. ”

“ When it has reached that stage, the only thing to be done, in my opinion, is to apply arsenious acid and destroy it.
Dr. Werner:—I look upon the treatment of a pulp principally from the standpoint of whether such pulp is absolutely necessary for the welfare of the tooth. The pulp is a formative organ. Its function decreases as the tooth develops. In young persons it is largest; grows smaller and smaller, and in old age it is nearly ossified or obliterated; that is, its retrogressive stage begins materially after the crown of the tooth erupts through the gum. ”

“ The pulp is of the consistency of milk when it pours from the spout of the pumps on the paper machine. The latter is a complicated series of rollers, belts, sieves, blankets, pumps, and gears, one hundred feet long. To describe it or to understand a description of it would require the vocabulary and the knowledge of a scientist. The milky pulp first passes over a belt of fine wire cloth, through which the water partly drains. It is ingeniously made to glide over two perforated iron plates, under which pumps are constantly sucking. ”

“ In the case of all fibers, whether rag or wood, painstaking work counts, and the excellence of the paper is largely dependent upon the time and care given to the reduction of the pulp from the original raw material. ”

“ Or the paper is placed in a test tube with a little water, the thumb placed over the mouth of the tube, and by shaking violently the paper is soon reduced to pulp. A very small portion of pulp is placed on the slide, and superfluous moisture carefully removed with filter paper. A stain makes the markings on the fibres more easily seen, and if a suitable stain is employed, some differentiation in colouring the various fibres takes place. ”

“ Sulphate Pulp.—The solvent used in making sulphate pulp is a mixture of caustic soda, sulphide of soda and sulphate of soda. Sprucewood, largely, is used and the pulp produced is exceedingly strong. Unbleached sulphate pulp is used, notably, in the making of Kraft wrapping-paper. ”

“ 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. ”

“ 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. ”

“ Now each of these four hundred plates, some twelve feet in length, has grown from a minute sort of bud, in the upper jaw. Its base is hollow, resting on the formative pulp which is developed from the gum. The pulp is understood to be the immediate origin of the hairy fringe, while a dense vascular substance, seated between the bases of the plates, forms the plate itself. When the plate reaches a certain length, its diameter has become greatly attenuated, and its tip is constantly breaking away, leaving the hair projecting. ”

“ The pulp is allowed to flow on to the wire cloth, so as to form a thick web of pulp. The bulk of the water passes away through the wire cloth; a further quantity is removed by the {97} vacuum-boxes and couch-rolls. The pulp, containing from 50 to 60 per cent. of water, is wound round an iron rod until a sufficiently large roll is formed.
The advantages of the presse-pâte system are the possibility of the removal of dirt and unboiled portions by means of the sand-tables and strainers, and the very complete washing and removal of the products of the action of bleaching powder. ”

“ Loss of strength may be due to impurities in paper, such as residues of the chemicals used in the preparation of the pulp, to the impurities in the pulp itself, or to the use of gas as the agent for lighting and heating. ”

“ 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. ”