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PAPER
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PAPER MANUFACTURE
In the See also:modern sense " paper " may best be described as a more Or less thin See also:tissue composed of any fibrous material, whoseindividual See also:fibres, first separated by See also:mechanical See also:action, are then deposited and felted together on See also:wire See also:cloth while suspended in See also:water (see FIBRES). The See also:main constituent in the structure of all See also:plants is the fibre or See also:cellulose which forms the casing or walls of the different cells; it is tfie woody portion of the plant freed from all See also:foreign substances, and forms, so to speak, the See also:skeleton of See also:vegetable fibre to the amount of 75 to 78%. Its forms and combinations are extremely varied, but it always consists of the same chemical elements, See also:carbon, See also:hydrogen and See also:oxygen, and in the same proportions. It is the See also:object of the paper-maker to eliminate the glutinous, resinous, siliceous and other intercellular matters and to produce the fibre as pure and as strong as possible. See also:Linen and See also:cotton rags, having already undergone a See also:process of manufacture, consist of almost pure fibres with the addition of fatty and colouring matters which can be got rid of by See also:simple boiling under a See also:low pressure of See also:steam with a weak alkaline See also:solution; but the substitutes for rags, See also:esparto, See also:wood, See also:straw, &c., being used as they come from the See also:soil, contain all the intercellular See also:matter in its See also:original See also:form, which has to be dissolved by strong chemical treatment under a high temperature. The vegetable fibre or cellulose, being of a tougher and stronger nature, is untouched by the action of See also:caustic soda (which is the chemical generally employed for the purpose), unless the treatment be carried too far, whilst See also:animal fibres or other organic matters are rendered soluble or destroyed by it. The cellulose, after its See also:resolution by chemical treatment, is still impregnated with insoluble colouring matters, which have to be eliminated or destroyed by treatment with a solution of See also:chlorine or See also:bleaching-See also:powder. The object of the paper-maker in treating any one particular fibre is to carry the action of the dissolving and bleaching agents just so far as to obtain the fibre as See also:free from impurities and as See also: Paper was first entirely made by See also:hand, See also:sheet by sheet, but in 1798 the invention of the paper See also:machine by See also: After further See also:thrashing and dusting, the rags are ready For boiling, the object of which is not only to get rid of the dirt still remaining in them and to remove some of the colouring matter, but also to decompose a particular glutinous substance which would impair the flexibility of the fibres and render them too harsh and stiff for readily making into paper. Various forms of vessels are used for boiling, but usually they are made to revolve by means of suitable gearing, and are either cylindrical or spherical (fg. 1). _se In these the rags are boiled with an alkaline solution under a low steam pressure for six to twelve See also:hours. The next step is that of washing and " breaking in," which takes See also:place in an See also:engine called the " breaker." This (fig. 2) is an oblong shallow See also:vessel or trough with rounded ends and dished bottom, usually about 13 ft. See also:long by 6 ft. wide, by about 2 ft. 6 in. in See also:depth, but the size varies greatly. It is partly divided along the centre by a See also:partition or See also:mid-See also:feather," and furnished with a heavy See also:cast-See also:iron See also:roll fitted See also:round its circumference with knives or bars of See also:steel in bunches or clumps. Underneath the roll and fixed in the bottom of the trough is the " See also:plate," consisting of a number of parallel steel bars bedded in a wooden See also:frame. The roll can be raised or lowered on the plate so as to increase or diminish, as desired, the cutting action of the bars and plate on the material. The See also:duty of the roll is to cut and tease out the rags, and also to See also:act as a lifter to cause the stuff to circulate round the trough. The breaker is See also:half filled with water and packed with the boiled rags; an ample supply of clean water is run Into the engine for washing the rags, the dirty water being withdrawn by the " See also:drum-washer," a hollow See also:cylinder fitted with buckets and covered with See also:fine wire-cloth. During the washing process the roll is gradually lowered on the plate to tease out the rags into their original fibres; this operation takes from two to four hours. As soon as all signs of the textile nature of the material are destroyed, the washing water is turned off, the drum-washer lifted, and a solution of chlorine or bleach is run in to bring the ppulpp up to the degree of whiteness desired, after which the rag " See also: The esparto, as shipped in See also:bales from the See also:Spanish or See also:African See also:fields, is mixed with roots, weeds and other impurities; and as most of these do not See also:boil or bleach as rapidly as the esparto they would, if not taken out of the pulp, show up in the finished paper as specks and spots. To get rid of them the esparto pulp when washed and bleached is run from the potcher into storage chests, from which it is pumped over a long, narrow See also:serpentine settling table or " sand-table," made of wood and fitted with divisions, or " weirs," behind which the heavy impurities or weeds fall to the bottom and are caught. The pulp is next passed over what is known as a " presse-pate " (fig. 4) or " half-stuff " machine, very similar to the wet end of a paper machine, consisting of strainers fitted with coarse-cut strainer plates, a See also:short wire and a pair of See also:couch and See also:press rolls. The pulp is See also:drawn by suction through the strainers, which keep back the finer impurities that have passed the sand-table, and then flows on to the wire-cloth in the form of a thick web of pulp. After pecoing through the couch and press rolls, the pulp leaves the machine with about 7o % of moisture, and is ready for the beating engine, the first operation of paper-making proper. This is the usual process, though various modifications are introduced in different mills and for different purposes. Most kinds of straw can be utilized for making into paper, the varieties generally used being See also:rye, See also:oat, See also:wheat and See also:barley; of these, the two former are the most important, as they give Straw. the largest yield in fibre. See also:Germany and France are the two principal users of straw, which closely resembles esparto in its chemical constitution, and is reduced to a pulp by a somewhat similar process. Scandinavia, Germany, the See also:United States and See also:Canada are the countries which mainly use wood as a material for paper-making. owing to their See also:possession of large See also:forest areas. They also export large quantities of wood-pulp to other countries. In Europe the Wood. Scotch See also:fir (Pinus sylvestris), the spruce (Picea excelsa), the See also:poplar (Populus See also:alba) and the See also:aspen (Populus tremula), are the timbers principally employed; and in See also:America the See also:black spruce (Picea See also:nigra), the See also:hemlock (Tsuga canadensis) , the poplar (Populus grandidentata) and the aspen (Populus tremuloides). 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 g"&Ip• In the manufacture of chemical wood-pulp, very greatabout seven or eight hours, in a similar manner to esparto and straw, though it requires much severer treatment. The steam pressure varies from 90 1b to as much as Igo lb per sq. in., and the amount of soda required is about 16% of Na2O, estimated on the barked and cleaned wood. The essential feature of the sulphite process is the employment of a solution of sulphurous See also:acid combined with a certain amount of See also:base, either See also:magnesia or See also:lime. As the acid reaction of the bisulphite solution would attack any ex-posed ironwork with which it comes in contact, the boilers in all cases should be lined with See also:lead. The type of boiler employed varies according to the process adopted. The principal See also:patents connected with the sulphite process are those of Tilghman, Ekman, _,.xor$WwPipe 11 lrr Il~~l~~lllllllllili 11 (sq. 11 llJlp'I See also:waste See also:Pipe advances have been made since 188o, and wood-pulp has grown to be one of the most important fibres for paper-making purposes. Two methods are in use, known respectively as the soda or alkaline process, and the sulphite or acid process, according as soda or See also:sulphur (or rather sulphurous acid) forms the base of the reagent employed. Trees of See also:medium See also:age are usually selected, varying from seventy to eighty years' growth and running from 8 to 12 in. in See also:diameter. They are felled in See also:winter and reach the mill in logs about 4 ft. long. After being freed from bark and the knots taken out by machinery, the logs are cut into small cubical chips about a to a in. in size by a revolving cutter. The chips are then bruised by being passed between two heavy iron rolls to allow the boiling solution thoroughly to penetrate them, and are conveyed to the boilers over a See also:screen of coarse wire-cloth, which separates out the fine sawdust as well as any dirt or sand. In the soda process the wood is boiled in large revolving or upright stationary boilers for See also:Francke, See also:Ritter-Kellner, See also:Mitscherlich, and Partington. The subsequent operations, in both the acid and alkaline processes of washing, bleaching and straining the pulp, are all very similar to those described for esparto. Wood-pulp produced by the sulphite process differs in a marked degree from that made by the soda process; the fibre in the former See also:case is harsher and stronger, and papers made from it are characterized by their hardness and transparency, whereas those made from soda pulp are softer and more mellow, corresponding in some way to the difference between linen and cotton fibres. Each class of pulp is largely used, both alone and mixed with other materials. Within See also:recent years important modifications and improvements have been adopted in the preparation of esparto and wood half-stuff with a view to reduce the cost of manufacture and See also:save waste of material. From the boiler to the beater the process becomes a continuous one, so that the prepared pulp requires practically no cc co handling till it is made into finished paper at the end of the machine; this effects a considerable saving in cost of labour and reduces the waste of material incidental to a See also:series of disconnected operations. From the potcher or breaking engine the esparto or wood pulp is discharged, by means of a patent circulator or See also:pump, into the first of a series of upright bleaching towers. These towers (fig. 5) are built up of wrought-iron rods and a special See also:kind of See also:cement. They are usually about i6 ft. high in the parallel by 81 ft. in diameter; the bottom of the See also:tower is conical and connected to a powerful circulator or pump, which discharges the pulp into the top of the tower and causes thereby a continuous circulation and a thorough mixing of the pulp and bleach. A special form of concentrator is fixed on the top of the first tower, which reduces the water in the pulp as it leaves the potcher to the minimum quantity necessary for per- fect circulation in the tower; by this means a considerable saving is effected in the quantity of bleach required. After the necessary concen- tration of the pulp in No. I tower, the bleaching liquor is added and the circulator at the See also:foot of the tower put in See also:motion. A two-way See also:valve in the See also:discharge pipe allows the pulp to pass on to tower No. 2, and so on through the series. The circulator in each tower is only put in working for a short See also:time once in every See also:hour and there is never more than one circulator working in the series at one time. There is no See also:manual labour in working the process, perfect cleanliness, and a great saving in See also:power over the old process. Each tower will hold about two tons of dry pulp. When the pulp is fully bleached in the last tower of the series, fresh water is run into it, and a second concentrator, similar to the one on the first tower, is put in motion and washes out all traces of the bleach in about 25 to 30 minutes. These concentrators effect also another purpose, taking to some extent the place of the presse-pate machine for removing roots, weeds and other impurities. From the last tower and concentrator the bleached pulp is pumped through a See also:line of pipes to the beaters, valves being fixed in the line of pipes to discharge into whichever beater is desired. These beaters are constructed in tower-form like the bleachers, the roll and plate being fixed on the top of the tower and the circulation effected in the same way as in the bleachers. Fig. 5 shows plan and elevation of such an arrangement of beaters and bleachers arranged in series. The beaters are made to hold each about t5oo lb of dry paper and a series of four of these can make from 55 to 6o tons of paper per See also:week. f/tiya //1,! 1//a/yiya//1////1//// ye/e/1/i/eay/N/e///1//1////0////0////////A- Fibres like jute,, hemp, See also:manila, &c., are chiefly used for the manufacture of coarse papers where strength is of more importance than See also:appearance, such as wrapping-papers, paper for See also:telegraph-forms, &c. The boiling processes for them are similar to those used for esparto and straw. The alkaline liquors in which rags, esparto and other paper-making materials had been boiled were formerly run into the nearest water-course; but now, partly because it is Soda insisted upon in England by the See also:Rivers Pollution Acts, Recovery. and partly because the recovery of the soda can be made remunerative, all these liquors are preserved and the soda they contain utilized. One of the best and most economical of the simple recovery plants is that invented by Potion, a See also:French distiller, and named after him. This consists of an evaporating chamber A, on the See also:floor of which a few inches of the liquid to be evaporated See also:rest. By the action of fanners B, B revolving at a high See also:speed and dipping into the liquid, it is thrown up in a fine spray through which the heated gases pass to the See also:chimney. After being concentrated in the evaporating chamber the liquid flows into the incinerating furnaces C,C, where the remaining water is driven off by the See also:heat of the See also:fire D, and the See also:mass afterwards ignited to drive off the carbonaceous matter. A considerable feature in this evaporator is Menzies and See also:Davis's patent See also:smell chamber E, a chamber filled with See also:masonry in which the strongly-smelling gases from the incinerating See also:furnace are allowed to remain at a red heat for a short time. After being recovered, the soda, in the form of crude carbonate, is lixiviated and re-causticized by boiling with See also:milk of lime. Porion's method is open, however, to the objection that the -whole of the sulphur in the See also:coal employed for the furnaces finds its way into the recovered soda, and forms sulphur compounds, thus reducing the value of the ash for boiling purposes; in addition, a considerable amount of soda is volatilized during the evaporation. By the application of the See also:system of multiple-effect evaporation to the recovery of waste liquors these drawbacks disappear, and an important See also:change has been made in the soda-recovery plant of the paper-mill. This system of multiple-effect evaporation, originally introduced by M. Rillieux, was perfected by the invention of See also:Homer T. Yaryan, of See also:Toledo, See also:Ohio, U.S.A. This type may here be taken for description, though other types of evaporator are now also employed, notably the ordinary See also:vertical See also:tube multiple effect evapor- ator as used for concentrating See also:sugar liquors. The Yaryan evapor- ator was originally applied in the United States to the concentration of the waste alkaline liquors of paper-mills; it then came into extensive use for the manufacture and refining of sugar, the See also:pro- duction of See also:glucose and a variety of other purposes. The principle of multiple-effect evaporation is to utilize the latent heat of a vapour given off from a liquid under a certain pressure to vaporize a further quantity of the liquid under a pressure maintained by mechanical means below that of the first. The essential feature which dis- tinguishes the Yaryan evaporator consists in the boiling of the liquor to be treated while it is passing through a series of tubes, which constitute a coil and are heated externally by steam or vapour. The quantity of liquor entering the coil is so controlled that it is only permitted partially to fill the tubes, and thus leaves See also:room for the instantaneous liberation of the vapour and its free See also:escape.' As the liquor descends from tube to tube it becomes concentrated and reduced in See also:volume until it ultimately passes into a " separator," where it impinges on a plate or disk, which causes a complete separation of the vapour and liquid; each then passes un to the next " effect," the liquid through the second coil of tubes and the vapour to the chamber enclosing them. This See also:combination of a series of tubes, or coil, and separator constitutes a vessel or " effect," and the evaporator consists of a series, usually three or more, of these vessels, one above the other (fig. 7). The vital feature, it will be understood, is therefore that the latent heat of the original steam, after per- forming its See also:function in the first effect, is passed on to the second and then to the third or more effects, in each of which an equal amount of work is done before passing to the final See also:condenser, where a vacuum is maintained. Thus, if the See also:total temperature be divided three times, the result is a triple-effect, if four times, a quadruple-effect. Taking an evaporation of 10 lb of water per See also:pound of coal, a single-effect apparatus will evaporate to lb of water, a ' In England, it should be stated, it is found that both for paper liquors and other liquors equally good evaporation results are obtained and the tubes kept cleaner by keeping them under a See also:head of liquor, i.e. the liquor is fed into the bottom See also:row of tubes and has to ascend row by row to the top row, from which it flows to the separator. Elevation See also:Scale of Feet gi93$$41I, 9'? 8/eaching Touter rte...._-d ra_s Motor! See also:Masson, See also:Scott and Co., Ltd. Beating Plant. t i ~ III O~ Plan 5/l///1/////////1/1///1///////1/1N///1/1H//////////p////1//1///////1////1//1//1///1//////. See also:double-effect 20 lb, a triple-effect 30 lb, and so on." The liquor to be concentrated is pumped from the storage tanks to the top or first effect of the Yaryan apparatus through a series of multiple-effect heaters, corresponding to the number of effects in the machine, by means of which the liquor is heated to as near the boiling point as possible of the liquor in the tubes of the first effect. The Mirrlees See also:Watson Co., Ltd. Live steam is introduced into the chamber surrounding the tubes of the first effect, and from the separator of the last effect the concentrated liquor is pumped to the incinerator. Any form of incinerating See also:hearth can be used in See also:conjunction with the multiple-effect evaporator, but one very suitable to the continuous work of, and the high degree of concentration produced by, the Yaryan machine is that known as the See also:Warren rotary furnace. This consists of a revolving iron cylinder lined with See also:brick, about 12 ft. long by Io ft. in diameter. The lining being 6 in. thicker at the inlet 2 than at the discharge, the interior of the furnace is conical in form so that the ash gradually See also:works forward and is eventually discharged fully burnt into trucks for storage, or on a travelling See also:band, and so carried automatically to the dissolving or lixiviating tanks. The strong liquor runs in at one end in a slow continuous stream; by the rotation of the hearth the burning mass is carried up the sides and drops through the See also:flame again to the bottom, much in the same manner as rags do in a revolving duster. In this way all the labour required to stir the ash of the ordinary hearth is dispensed with, and the burning material comes continuously in See also:close contact with the flame, a complete and thorough See also:combustion being the result. The fire-See also:box is situated at the delivery end of the furnace, and is mounted on trucks so that it can be run back when cleaning or repairing the See also:brickwork. The waste heat is utilized in raising steam in a steam boiler set behind the furnace, and often in keeping the thick liquor hot after leaving the evaporator and before entering the rotary furnace. Paper-making proper from prepared pulp, whether of rags, esparto, wood or other raw material, may be said toi begin with the operation technically known as " beating " which is i The figures given here are theoretical rather than actual. In practice a double effect is not capable of evaporating twice as much with i lb of coal as a single-effect, owing to loss' of efficiency through See also:radiation, &c. 2 This was the original Warren principle, but has largely been abandoned in favour of a parallel brick lining throughout; the ash gradually works forward and is discharged as described. A later method is to build the fire-box on the descending side of the rotary furnace, while a specially constructed door and ash discharge shoot are provided at the ascending side, which gives See also:access to the inside of the furnace and provides all the other essentials without the loss of heat which resulted from the portable fire-box, due to leakage between the box and the rotary furnace proper.carried out in one of the various forms of beating engine or " Hollander." The object of the beater is to reduce the fibres to suitable lengths and also to See also:beat or bruise them into a stiff pulp of sufficient consistency to absorb and carry the water necessary to See also:felt them together on the wire- Masson, Scott & Co., Ltd. Fin. 8.-See also: In the pipe is fixed a two-way valve, so that when the beating operation is complete the finished pulp can be run into the stuff-chests of the paper machine. The advantages of this form of beater are that a quicker and more thorough circulation of the pulp takes place than when the roll has to do the double duty of making the pulp travel and beating it up at the same time, and thus tends to reduce the time of the operation. Also more bars can be fixed in the roll, increasing its effect on the pulp, and less power is required than when the roll revolves in the middle of the stuff as in the ordinary form of beater. Beating engines of quite a different construction are now largely used in See also:American mills, and also to some extent in Great Britain. These are known as " refiners," and the most important forms are the See also:Jordan and Kingsland beaters (so called from the names of the inventors), or modifications of them. The first (fig. 9) consists of a conical plug or roll fixed on a See also:shaft and revolving at a high See also:rate of speed within an See also:outer casing of corresponding shape; both the plug and the casing are furnished with steel bars parallel with the shaft, but set at slightly different angles, taking the place of the bars in the roll and plate of the ordinary beater. This conical plug or roll can be moved in either direction parallel to its See also:axis and by this means the cutting action Beating, of the two sets of bars can be increased or reduced. The pulp flows into the top of the beater at the smaller end of the See also:cone through a box provided with an arrangement for regulating the flow and passes out through an opening in the casing at the other end. The roll or plug revolves at from 350 to 400 revolutions per See also:minute, and requires a power to drive it of from 25 to 40 h.p., Tirflowthe machine process. Only the finest qualities of rags are used for hand-made paper; and the preparation of the half-stuff is the same as that already described under treatment of rags. The pulp after being prepared in the beating engine is run into Paper-maker according to the work to be done, and one engine is capable of passing as much as moo lb See also:weight of dry pulp per hour. The Kingsland beater consists of a circular box or casing, on both inside faces of which are fixed a number of knives or bars of steel or bronze; inside the case is a revolving disk of See also:metal fitted on both sides with corresponding and similar bars. The contact between the revolving and stationary bars can be regulated, as in the Jordan engine, to give the required amount of beating action on the pulp. The refiner is essentially a See also:finishing process as an See also:adjunct to the beating process proper. The advantages to be derived from its use are a considerable saving in the time occupied in beating and the See also:production of a more See also:uniform and evenly divided pulp, particularly where a mixture of different fibres is used. By the use of the refiner the time occupied in the beater can be reduced by nearly one-half, the half-beaten pulp passing through the refiner from the beater on its way to the paper-machine. It is not, however, generally employed for the best kinds of paper. During the operation of beating various materials and chemicals are added to the pulp for the purposes of sizing, loading, colouring, &c. Papers for writing and most of those for printing purposes must be rendered non-absorbent of See also:ink or other liquid applied to them. To effect this some form of animal or vegetable size or See also:glue must be applied to the paper, either as a coating on the finished web or sheet, or mixed with the pulp in the beating engine. The former, called " tub-sizing" will be described later; the latter which is known as " engine-sizing" consists in filling up the interstices of the fibres with a chemical precipitate of finely-divided See also:resin, which, when dried and heated on the cylinders of the paper-machine, possesses the See also:property of being with difficulty wetted with water. Except in the very best qualities of paper, it is usual to add to the pulp a certain quantity of cheap loading material, such as See also:china-See also:clay or See also:kaolin, or See also:pearl-hardening, a chemically precipitated form of sulphate of lime. The addition of such loading material to a moderate extent, say to to 15%, is not entirely in the nature of an adulterant, as it serves to close up the pores of the paper, and for ordinary writing, printing and lithographic papers renders the material softer, enabling it to take a much better and more even See also:surface or glaze. But if added in excess it is detrimental to the strength and hardness of the sheet. Most materials, however well bleached, have a more or less yellowish tinge; to produce the desired white shade in the paper certain quantities of red and See also:blue in the form of See also:pigments or dyes must be added to the pulp. The blues usually employed are See also:ultramarine, smalts and the See also:aniline blues, while the red dyes are generally preparations of either See also:cochineal or the aniline dyes. Other See also:colours are required in the manufacture of papers of different tints, and with one or two exceptions they must be mixed with the pulp in the beater. There are two distinct processes of producing the finished paper from the pulp, known respectively as " hand-made " Paper and " machine-made." The expense of manumachine. facture of hand-made paper and the consequent high price render it too costly for ordinary use; the entire process on the machine occupies a few minutes, while in the ordinary state of the See also:weather it could not be done by hand in less than a week. A brief description of the hand-made process will suffice and it will at the same time facilitate the right comprehension of large chests from which the vat is supplied; before reaching this it is strained as on the paper-machine (see below). The sheet of paper is made on a See also:mould of fine wire-cloth with a removable frame of wood to keep the pulp from running off, extending slightly above the surface of the mould, called the " deckel." To form the sheet, the paper-maker dips the mould into a vat (see fig. ro) containing the prepared pulp, lifting up just so much as will make a sheet of the required thickness; as soon as the mould is removed from the vat, the water begins to drain through the wire-cloth and to leave the fibres on the surface in the form of a coherent sheet, the felting or intertwining being assisted by a lateral motion or " shake " given to the mould by the Workman; the movable deckel is then taken off, and the mould is given to another workman, called the " coucher," who turns it over and presses it against a felt, by this means transferring or " couching " the sheet from the wire to the felt. A number of the sheets thus formed are piled one above another alternately with pieces of felt, and the whole is subjected to strong pressure to expel the water; the felts are then removed and the sheets are again pressed and dried, when they are ready for sizing. Any See also:pattern or name required in the sheet is obtained by making the wire-cloth mould in such a way that it is slightly raised in those parts where the pattern is needed (fig. II); consequently less pulp lodges there and the paper is proportionately thinner, thus showing the exact counterpart of the pattern on the mould; such are known as " watermarks." The expense of manufacturing paper in this way is very much greater than by machinery; but the gain in strength, partly owing to the time allowed to the fibres to knit together, and partly to the free expansion and contraction permitted them in drying, still maintains a steady demand for this class of paper. The paper-machine (fig. 12) consists essentially of an endless mould of fine wire-cloth on which the pulp flows and on which a continuous sheet of paper is formed; the sheet then passes through a series of press rolls and over a number of steam-heated cylinders until it is dry. From the beating engines, the pulp is emptied into storage tanks or stuff-chests, fitted with revolving arms or See also:agitators; from these the pulp is pumped into a long upright supply box at a higher level, called the stuff box, which communicates with the sand See also:trap or table by means of a regulating valve. With the pulp a certain amount of water is allowed to flow on to the sand trap so as to dilute it sufficiently to form on the wire-cloth of WET IIp IRIIIIRIOUIhIfl Vllfih v =1 1 °111iilll "See also:face of a rapidly-revolving disk driven by a pair of speed-cones, so that the speed of the shake can be altered. The object of this shake is to interlace the fibres together, but it also assists in keeping the water from passing through the wire too rapidly before the paper has been properly formed. Most machines have two suction-boxes with the See also:dandy-roll " revolving between them on the top .A -------------------- END r _ tet Preis i Rolla M • `4... ,q $}ra o~ pus R~yOO D,,,dy Couch Rolla r ~`C C ' I Is I ~ ilmuu n i vunw inumm~ II11 ~ d 1 il~ , x nl o IN RN~ ~ r ^t .: ~nPihuiGV-~I~.!u{~Nly^ B! moment it spreads on the wire until it arrives at the first suction- box, where the web is sufficiently dry to retain its edges. The frame of the machine from the See also:breast-roll to the first shake. suction-box is hung on a pair of strong hinges, and is capable of a slight See also:horizontal motion imparted by a horizontal connecting-See also:rod, one end of which is eccentrically keyed on to thepieces of wire are soldered representing the watermark water-to be reproduced in the paper. From the last suction- marking box the half-dried sheet of pulp passes between the and " couch-rolls," so called from the corresponding operation Gouchingt of couching in hand-made paper, which, by pressing out most of the remaining moisture, impart sufficient consistency to the paper to enable it to leave the wire; both rolls are covered with a felt jackets and the top one is provided with levers and weights to increase or diminish the pressure on the web. The paper is now fully formed, and is next carried by means of endless felts Pressing between two and sometimes three pairs of press-rolls and Dryings, to See also:extract the remaining moisture, and to obliterate as much as possible the impression of the wire-cloth from the under-side of the web. The web of paper is finally dried by passing it over a series of hollow steam-heated drying cylinders driven one from, the other by gearing. The slower and more See also:gradual the drying process the better, as the change on the fibres of the web due to the rapid contraction in drying is thereby not so excessive, and the heat required at one time is not so great nor so likely to damage the quality of the paper; the See also:heating surface should therefore be as large as possible, and a great number of cylinders is required now that .the machines are driven at high speeds. The cylinders are so placed that both surfaces of the web are alternately in contact with the heating surface. All the. cylinders, except the first two or three with which the moist paper comes in contact and where the greatest evaporation occurs, are encased by continuous travelling felts. The drying cylinders are generally divided into two sets between which is placed a pair of highly polished chilled iron rolls heated by steam, called " nip-rolls," or " smoothers," the purpose of which is to flatten or smooth the surface of the paper while in a partially dry See also:condition. Before being reeled up at the end of the machine the web of paper is passed through two or more sets of " calenders," according to the degree surfacing. of surface or smoothness required. These calenders consist of a vertical stack of chilled iron rolls, generally five in number, revolving one upon another, and one or more of which are bored and heated by steam; pressure can be applied to the stack as required by means of levers and screws. The web of paper is now See also:wound up in long reels at the end of the machine. Paper-machines are now usually driven by two See also:separate steam engines. The first, running at a See also:constant speed, drives the strainers, pumps, shake motion, &c., while the second, working the paper-machine, varies in speed according to the rate at which it requires the paper-machine. The sand trap consists of an elevated table ~ of the pulp (so called because it can be made to give to the paper in which is sunk a shallow serpentine channel lined on the bottom any desired water-marking). The " dandy-roll " (fig. 13) is a See also:light with rough felt and divided throughout its length by a number of skeleton cylinder covered with wire-cloth on which small small strips of wood, behind which the impurities collect as the pulp flows over them on its way to the strainers. The strainers are made of plates of See also:brass or some hard and durable See also:composition with fine parallel slits cut in them, through which the Straining. fibres pass, all knots and improperly divided portions remaining behind; the pulp is made to pass through them by the rapid vibration of the plates themselves or by a strong suction underneath them, or sometimes by a combination of the two. From the strainers the pulp flows into a long wooden box or trough, of the same width as the paper machine, called the " breast-box," and thence on to the wire-cloth. The wire consists of a continuous See also:woven brass cloth, supported horizontally by small brass rolls, called " tube-rolls," carried on a Fanning et frame; it is usually 40 to 50 ft. long and is stretched the She. tight over two rolls, one at each end of the frame, called respectively the " breast-roll " and the " lower-couch roll." The ordinary See also:gauge for the wire-cloth is 66 meshes to the See also:inch for writings and printings; finer wires are sometimes used, however, up to 8o to the inch; for lower grades the mesh is coarser. The water, mixed with the pulp, flows from the wire-cloth by See also:gravitation along the lines of contact between it and the tube-rolls; this water, which contains a considerable percentage of fibre, especially from finely beaten pulps, drops into a See also:flat See also:copper or wooden See also:tray, from which it flows into a tank and is pumped up with the water for diluting the pulp so that none of it shall be wasted. From the tube-rolls the wire conveys the pulp over a pair of suction-boxes for extracting the remaining water from the web. The width of the web of paper is determined by two continuous straps of See also:vulcan- ized See also:rubber about 11 in. square, one on each side of the wire, called the " deckel-straps "; the distance between these straps can be increased or diminished; they serve to See also:guide the pulp from the to be driven. The power consumed by the two engines will See also:average from 40 to 100 h.p. The drying cylinders of the paper-machine form a convenient and economical condenser for the two steam-engines, and it is customary to exhaust the See also:driving engine into the drying cylinders and utilize the latent heat in the steam for drying ,the paper, supplementing the supply when necessary with live steam. The speed of the machine has frequently to be altered while in motion. An alteration of a few feet per minute can be effected by changing the driving-speed of the steam-engine See also:governor; for a greater change the machine must be stopped and other driving-wheels substituted. Arrangements are made in the driving-See also:gear by which the various parts of the machine can be slightly altered in speed relatively to one another, to allow for the varying See also:con-See also:traction or expansion of the paper web for different kinds and thicknesses of paper. The average speed of a paper-machine on fine writing, papers of medium weight is from 6o to 90 ft. per minute, but for printing-papers, See also:newspapers, &c., the machine is driven from 12o up to as much as Soo and 400 ft. per minute. The width of machines varies greatly in different mills, from about 6o in. to as much as 15o in. wide. Mills running on higher classes of papers as a See also:rule use narrow machines, as these make a closer and more even sheet of paper than wider ones. On fine writing-papers an average machine will make from 20 to 40 tons per week, while for See also:common printing and newspapers the weekly output will amount to 50 to 70 tons. All hand-made papers, and many of the best classes of machine- made papers, instead of being sized in the beater with a preparation rub-sizing. of resin are what is called " tub-sized," that is, coated with a solution of See also:gelatin. Such papers, when machine- made, are reeled off the machine straight from the drying cylinders in the rough state. The web is then led slowly through a tub or vat containing a heated solution of animal glue or gelatin mixed with a certain amount of See also:alum; after passing through a pair of brass rolls to squeeze out the superfluous size, the web is reeled up again and allowed to remain for some time for the size to set. The paper is then led by means of continuous travelling tapes over a long series of open skeleton drums, about 4 ft. in diameter, inside J. Milne & Son, Ltd. The bottom roll and the 3rd, 6th, 8th and loth rolls, all reckoned from the bottom, are made of highly polished chilled cast-iron; the others of highly compressed paper. which revolve fans for creating a circulation of hot See also:air; rows of steam-pipes underneath the line of drums furnish the heat for drying. Slow and gradual drying is essential to this process to get the full benefit of the sizing properties of the gelatin. In hand-made papers, the sheets are passed by handfuls of three or five on an endless felt through the gelatin solution and between a pair of rolls, and then slowly dried on rope lines or " tribbles " in a steam-heated and well-ventilated See also:loft. The cheaper kinds of paper are glazed on the paper-machine in the calenders as before described. For the better class or very highly-glazed papers and those that are tub-sized, a C3lazirg or subsequent See also:glazing process is required; this is effected SarPaciny. by sheet or plate-glazing and by super-calendering or web-glazing. The plate-glazing process is adopted mainly for the best grades of writing-papers, as it gives a smoother, , higher and more permanent See also:gloss than has yet been imitated by the roll-See also:calender. In this method each sheet is placed by hand between two See also:zinc or copper plates until a See also:pile of sheets and plates has been formed sufficient to make a handful for passing through the glazing-rolls; this handful of about two quires or 48 sheets of paper, is then passed backwards and forwards between two chilled-iron rolls gearing together. A considerable pressure can be brought to See also:bear upon the top roll by levers and weights, or by a pair of screws; the pressure on the rolls, and the number of times the handful is passed through, are varied according to the amount of gloss required on the paper. The super-calender (see fig. 14) is used to imitate, the plate-glazed surface, partly as a matter of See also:economy in cost, but principally for the high surfaces required on papers for books and See also:periodicals to show up wood-cuts and photographic illustrations. It usually consists of a stack of chilled cast-iron rolls, alternating with rolls of compressed cotton or paper so that the web at each nip is between cotton and iron; it will be seen from the See also:illustration that there are two cotton rolls together in the stack for the purpose of See also:reversing the action on the paper and so making both sides alike; pressure is applied to the rolls at the top by See also:compound levers and weights or screws. A very high surface can be quickly given to paper by See also:friction with the assistance of heat; the process is known as " burnishing," and is used mostly for envelope papers and wrappings where one surface only of the web is required to be glazed. It is produced by the friction of a chilled-iron roll on one of cotton or paper, the ratio of the revolutions being as 4 to 5; steam is admitted to the burnishing iron roll. At the end of the 19th century a large and increasing demand sprang up for papers embossed with a special pattern, such as linen-finish, &c.; these are used principally for See also:fancy writing-papers, programmes, menu-See also:cards, &c. This See also:embossing is effected usually on the plate-glazing machine, in the. case of linen and similar finishes by enclosing each sheet of paper between two pieces of linen or other suitable material to give the desired texture or pattern on the surface of the sheet. Each sheet of paper with its two pieces of cloth is placed between zinc plates and passed backwards and forwards between the rolls of the machine as in plate-glazing. Except for special purposes, such for example as for use in a continuous printing-machine, paper is usually sent from the mill in the form of sheets. A number of reels of paper is cutting.
hung on spindles between two upright frames to feed
the cutting-machine (see fig. 15); the various webs of paper are drawn forward together through two small rollers, and ripped into widths of the required size by means of a number of pairs of circular knives or " slitters "; they then pass between another pair of rollers, and over a long dead-See also:knife fixed across the cutting-machine, on which they are cut into sheets by another transverse knife fastened to a revolving drum and acting with the dead-knife like a large pair of shears. The cut sheets then fall upon an endless travelling felt, from which they are stacked in piles by boys. It is often necessary, as in the case of water-marked papers, that the sheets should be cut with great exactness so that the designs shall appear
See also: Writing Papers. Drawing and See also:Book Papers. Printing Papers. Inches. Inches. Inches. See also:Pott . . 122 X 15 Demy. 151 X 20 Demy 171 X 221 Foolscap 13i X 161 Medium . 174 X 221 Double demy 221 X 35 Double foolscap 162 X 261 Royal 19 X 24 Quad demy . 35 X 45 Foolscap and third. 134 X 22 Super-royal 194 X 27 Double foolscap 17 X 27 Foolscap and half . 134 X 241 Imperial 22 X 30 Royal . . 20 X 25 Pinched post . 141 X 182 See also:Elephant 23 X 28 Double royal . 25 X 40 Small post . 154 X 19 Double elephant. 261 X 40 Double See also:crown 20 X 30 Large post 161 X 21 See also:Colombier . 231 X 341 Quad crown . 30 X 40 MeDoudibleuml. large post . . 1218 X X 23 33 See also:Atlas .1 Antiquarian . 26 X 34 31 X 53 Imperial 22 X 30 different shades of colour, &c.; this entails considerable time and Of not less importance are the qualities which belong to paper expense as each sheet has to be passed in See also:review separately. as a chemical substance or mixture, which are: (a) its actual composition; 2 the liabilit to change under whatever con- the trade respectively as "perfect," "retree " and " broke "; the ditions of storage and use it may be subjected to. For all best of the defective sheets form the second quality "retree," a papers to be used for any permanent purpose these See also:physical See also:term derived from the French word retirer (to draw out), and are and chemical qualities must ultimately See also:rank as regulating the to the mill to be repulped as waste paper. In England and See also:Wales in 1907 there were 207 mills, using 09 Paper is sold in sheets of different sizes and is made up machines and 99 vats for hand-made paper; in See also:Scotland, 59 mills into reams containing from 480 to 516 sheets; these sizes and iii machines; in See also:Ireland, 7 mills and II machines. A rough estimate o the rmed onf the basis tunt See also:hat averpage m lls wou d represent f om £20000 The table at foot of See also:page shows the amounts and values of the See also:British imports and exports of paper and paper-making materials in 1907. of the Paper-trade," Cantor Lectures, Society of Arts (See also:London, 1877) ; Clapper- ton, See also:Practical Paper-Making (London, 1894) ; See also:Cross and Bevan, See also:Report on See also:Indian Fibres and Fibrous Substances (London, 1887) ; id., Cellulose (London, 1895–1905) ; id., A See also:Text-Book of Paper- Making (London, 1888) ; See also:Clayton See also:Beadle, Chapters on Paper-Making (London) ; Davis, The Manufacture of Paper (Phila- delphia, 1886) ; Dropisch, See also:Die See also:Papier Machine (See also:Brunswick, 1878) ; id., Papier- With the enormously increased production of paper and the fabrikation (with atlas) (See also:Weimar, 1881) ; See also:Griffin and Little. The eat reduction in See also:rice within recent it has been found I See also:Chemistry of Paper-making (New See also:York, 1894)T; See also:Herzberg, Papier- $r price years, .prufung (See also:Berlin, 1888; Eng. trans. by P. N. See also:Evans, London); t paper-making id., Mikroskopische Untersuchung See also:des Papiers (Berlin, 1887); See also:Hof- See also:mann, Handbuch der Pa ier fabrikation (Berlin, 1897) ; Hoyer, Fabrikation des Papiers (Brunswick, 1886) ; Indian See also:government, Report on the Manufacture of Paper and Paper Pulp in Burmah (London, 1906); See also:Schubert, Die Cellulose fabrikation (Berlin, 18S7); id., Die Praxis der Papierfabrikation (Berlin, 1898) ; id., Die Holz- stoff-See also:oder Holzschliff-fabrikation (Berlin, 1898); Sindall, Paper Technology (London, 1904–1905); " Report of the See also:Committee on the Deterioration of Paper," Society of Arts (London, 1898); See also:Wyatt, " Paper-making," Proc. Inst. C. E., lxxix. (London, 1885) ; id., " Sizing Paper with See also:Rosin," Proc. Inst. C.E., xci. (London, 1887); Paper-Makers' Monthly See also:Journal (London, since 1872); Paper- Trade Journal (New York, since 1872); Papier-Zeitung (Berlin, since 1876). (J. W W)
See also:India Paper.—This name is given to a very thin and light
but tough and opaque kind of paper, sometimes used for
printing books—especially Bibles—of which it is desirable to
reduce the bulk and weight as far as possible without impairing
their durability or diminishing their type. The name was
originally given in England, about the middle of the 18th century,
to a soft absorbent paper of a See also:pale See also:buff shade, imported from See also:standards that the " See also:science " of has scarcely
of Quality. advanced with the same rapid strides as the See also:art
itself. Although a sheet of paper made to-day differs
little as a fabric from the papers of earlier epochs, the introduc-
tion of new and cheaper forms of vegetable fibres and the
See also:auxiliary methods of treating them have caused a great change
in the quality, strength and lasting power of the manufactured
See also:article. The undue introduction of excessive quantities of
mechanical or ground wood-pulp in the period 1870–1880 into
the cheaper qualities of printing-papers, particularly in Germany,
first See also:drew See also:attention to this matter, since it was noticed that
books printed on paper in which much of this material had been
used soon began to discolour and turn See also: Value. Tons. £ Tons. £ Paper, unprinted 268,036 3,917,954 Paper, printed 11,494 621,293 Straw- and millboards . . . 164,381 1,134,568 87,055 2,342,420 443,911 5,673,815 Rags, linen and cotton . . 20,039 206,151 122,909 752,739 Esparto and other vegetable fibres 202,523 738,834 (including other Wood-pulp— paper making Chemical 282,098 2,396,856 materials.) Mechanical 192,756 915,491 607.416 4,257,332 to numerical expression. The result of these investigations has I China, where it was made by hand on a paper-making frame been the fixing of certain standards of quality for papers intended generally similar to that used in Europe. The name probably for different purposes. These qualities are grouped and defined under such heads as the following: Strength, expressed in terms of the weight or See also:strain which the paper will support. Elasticity and texture, measured by See also:elongation under strain and resistance to crumpling or rubbing. Bulk, expressed in the precise terms of specific gravity or weight per unit of volume.
originated in the prevailing tendency, down to the end of the 18th century, to describe as " Indian " anything which came from the Far See also:East (cf. Indian ink). This so-called India paper was used for printing the earliest and finest impressions of engravings, hence known as " India proofs."
The name of India paper is now chiefly associated with
See also:European (especially British) machine made, thin, opaque
printing papers used in the highest class
of book-printing. In 1841 an See also:Oxford
See also:graduate brought See also:home from the Far
East a small quantity of extremely thin
paper, which was manifestly more opaque
and tough, for its weight, than any paper
then made in Europe. He presented it
to the Oxford University Press, and in
1842 See also: The paper, when subjected to severe rubbing, instead of breaking into holes like ordinary printing paper, assumed a texture resembling See also:chamois See also:leather, and a See also:strip 3 in. wide was found able to support a weight of 28 lb without yielding.
The success of the Oxford India paper led to similar experiments by other manufacturers, and there were in 1910 nine mills (two each in England, Germany and See also:Italy, one each in France, See also: Additional information and CommentsThere are no comments yet for this article.
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