Page:The American Cyclopædia (1879) Volume XIII.djvu/57

 PAPER hyposulphite of soda; sulphite of calcium is also used. The engine heing put in motion, the cylinder is brought down upon the block by degrees, so that in the course of three or four hours the rags are beaten into a fine pulp. When the operation is nearly completed, the paper may be colored or given a bluish tint, by the use of ultramarine, Prussian blue, indigo, aniline blue, or oxide of cobalt. Paper may be sized in the engine or in the paper-making machine; the materials used are different in the two cases. There are various prescriptions for engine size; the most common is called resin size, made by adding a solution of alum to a resin soap dissolved in soda. It is beaten up and mixed with the pulp in the beating engine before being delivered to the vat from whence it is distributed to the paper-making machine. Sizing for the machine, where the size is applied to the paper, is made of gelatine ; and manufacturers generally make their own size, in a room adjoining that which contains the machine, so that it may be used while in solution, by which time in dissolving and pre- paring and other expense is saved. It is made of the best hide clippings, which, being soft- ened and soaked several days in large wood- en tubs of water, are then put into wooden cylinders from 4 to 6 ft. in diameter and about 10 ft. long, revolving on a horizontal shaft, by which means they are washed and cleansed of dirt. They are then put into a tub 6 or 8 ft. in diameter, made of wood or galvanized iron, and having a perforated false bottom, beneath which steam is introduced through a coil of pipe perforated with many holes. The water is not boiled, but raised to about 185 F. and kept at that point for 12 or 18 hours, dissolving the gelatine. The latter being strained, enough alum is added to it to give a slight astringent taste, which prevents fermentation and also stickiness, and adds body to the paper. Within a few years clay, china clay, and kaolin have been added to the pulp, mainly to increase the weight of the paper. The alumina of these substances has a strong affinity for vegetable matter and adheres closely to the fibres. The clay must be put into the engine before the size, as it will then reach the fibres, and the size surrounding both will better fasten the clay. All kinds of paper will carry from 5 to 15 per cent, of clay without size, and it is asserted that a small addition of it to the pulp improves some kinds of paper, making them smoother and more opaque; but too great a quantity weakens the paper and makes it brittle. 2. Waste paper is dusted and sorted in the same way as rags. It is then boiled and printers' ink stains removed by soda, which unites with the oil, leaving the color to subside. The boil- ers are stationary, so that the paper shall not be reduced to pulp too soon, and thus incorpo- rate the coloring matter of the ink. The wa- ter is continually changed, producing a current which after a while removes the dirt. The material is put through the washing, bleach- 634 ing, and beating engines as in the reduction of rags, although the bleaching and beating pro- cesses occupy much less time. 3. Straw is cut into short lengths with cylindrical cutters and then boiled with caustic soda. (See SODA.) It may here be stated that straw, wood, and other coarse vegetable fibre is generally boiled with caustic soda under high pressure to dissolve the resinous and gummy matters which hold the fibres together. The caustic soda, or soda ash of commerce, contains too much carbonic acid to answer the purpose of the paper maker. It must be made more caustic, and this is ac- complished by the addition of caustic lime, by which the carbonic acid is removed in the form of carbonate of lime. The soda solution, after having been sufficiently acted upon by cream of lime, and the resulting carbonate having sub- sided, is let into revolving boilers (which may be heated by steam or by the direct application of fire, the latter being preferred), which have been previously carefully packed full of the cut straw. A boiler 16 ft. long and 6 ft. in di- ameter will hold about 2,500 Ibs. of the straw, if carefully packed. Two or three boilers are sometimes connected for the purpose of saving fuel by blowing out the steam from one to another. After digestion the material, which answers to half stuff, is washed, bleached, and reduced to pulp in engines in much the same way as with rags. This process is known as Mellier's ; more recent ones by Dixon, Ladd, Cresson, Keene, and others, by which the boil- ing is performed under much greater pressure, thus shortening the time, have been introduced. The pulp is usually made into paper on a cyl- inder machine. 4. Esparto grass, a spontane- ous growth of the gravelly and sandy soils of eastern Spain and northern Africa, where it has for centuries been made into matting and baskets, is treated in a similar manner to straw, but makes a superior paper, as its fibres are tougher. It may be made into paper either on a cylinder or a Fourdrinier machine. 5. Wood. Paper was made from wood as early as from straw, but only on a small scale till the erec- tion of the works of the American wood paper company. Charles Watt and Hugh Burgess patented the invention in England in 1853 and in the United States in 1854. One of the establishments of the company, at Manayunk, Pa., has a capacity for making 15 tons of wood pulp a day. The works were built in 1865, at a cost of $500,000. The wood used is chiefly American poplar or whitewood. It is cut into slices about half an inch thick, across the grain, being fed to a rotary disk cutter armed with strong knives in the form of cord wood 5 ft. long. One of the cutters will daily reduce 40 cords of wood to chips. The chips are placed in upright cylindrical boilers about 5 ft. in diameter and 16 ft. high, with hemispheri- cal ends, and provided inside with perforated diaphragms, each space holding a quantity of chips equal to a cord of wood. A solution of caustic soda having a strength of 12 Baum6 is VOL. XIII.-