PROCESS OF ALAN UFACTURE BY MACHINERY.
Whether for hand-made or fur maelone-made paper, the preparation of rags for pulp may be divided as follows: ( 1 ) (leaning: (2) boiling; (3, washing: (4) bleaching: 1 5) beating or re ducing to pulp. The preparation of substitutes for rags is practically (lie same except that the boiling process is more drastic, varying with the substance used.
(1) Clc(ming.—Rags are received at the mill in bales more or less sorted into white. colored, linen, cotton, canvas. etc., but need. for the finer sorts of paper (in which alone rags are now used at all I, a thorough dusting and further sorting by hand. The duster may lie of various forms, and removes dust and foreign substanees by vigorous mechanical methods. The sorting is done by girls who stand before tables covered with wire screens through which dust and dirt sifts. The girls cut otT buttons. rubber (a great curse to the modern paper-maker. as it does not bleach and appears in the paper as black specks, besides sticking to rolls and clogging the straining screens), and other for eign substances. and sort the rags accurately into different grades. A further dusting and chopping into pieces a couple of inches long make the rags ready for boiling.
(2) Boiling.—The rags are packed in a large horizontal boiler. called the 'rotary.' 'I'his is provided with manholes for the admission and discharge of the rags and lime. and is mounted on hollow trunnions through which steam is admitted. To elean the rags from all fatty, colored, and non-cellulose impurities. a solution of lime is used, and the rags cooked and slowly rotated under steam pressure for several hours, the amount of lime, pressure. and time of boiling varying according to circumstances. When sutli cielitly cooked, the steam and liquor are blown MI and the in dumped out by slowly the rotary with the manholes opened. The rags are now of a brown color, and most of the impurities have been saponified, combining with the lime to form insoluble compounds which eau be washed away, or. in the ease of colors,
reduced to simple colorless compounds.
(3) Trnshing.—The washing or beating en gine is shown in the cut. It is also called the Tlollander. It consists of a woolen or metal tub 10 to 1S feet long, with rounded ends (see cut 1. in the centre of which is a partition (E) called the 'mid-feather ; a roll (C) is provided with knives, and revolves rapidly over a bed plate (B) of similar knives. The distance be tween the bed plate and the roll is regulated by raising or lowering the supports of the roll with a wheel and screw. The rags after passing between the bed plate and the roll flow down the 'backfall' (A) and around the mid-feather back to the starting point. as indicated by ar rows. The washing engine is provided with a washing cylinder (D), which is so made that as it revolves it scoops up the water. which flows out through its axis, the rags being kept out by a fine wire cloth surrounding the cylinder. The rags to be washed are put into the washing engine' with enough water, the roll being raised so that the rags pass around freely without being beaten into pulp, as otherwise the dirt would be ground into the fibre. A large quantity of water is admitted, which is removed by the drum washer, as described above, and the rags are in this manner rapidly cleaned. The roll is now lowered gradually, and the rags slowly macerated. losing their characteristics of tex tiles, and being finally resolved into single fibres tub is often used. In place of chloride of lime, a s'olution much used in France is prepared by electrolysis of magnesium chloride. After bleach ing, the pulp is emptied into the drainers, large chambers with floors of porous tiles, where the moisture and surplus bleach drain off. The pulp is left. sonic days in the drainers. till it is nearly dry. In Europe, in place of drainers, the pulp is usually dried by making up into thick sheets of paper on a machine similar to the wire of the Fourdrinier machine called a yresse te.