The vats were superseded by what are called engines, a Dutch invention well adapted to the purpose. The engines are sometimes arranged in pairs on different levels, the bottom of one being higher than the top of the other, so that the contents of the higher engine may be let off into the lower. In the upper engine, called the washer, the rags are first worked coarsely with a stream of water running through them to wash and open their fibres: this reduces them to what is called half stuff; they are then let down into the beating engine to be ground into pulp fit for making paper. Each engine consists of a large wooden vat or cistern V V, Figs. 3, 4, of oblong figure on the outside, with the angles cut off; the inside, which is lined with lead, has straight sides and circular ends. Or the vat may be entirely formed of cast-iron. It is divided by a partition P P, also covered with lead. The cylinder C is firmly fixed to the spindle s, which extends across the engine, and is put in motion by the pinion w, which engages other wheels set in motion by water or steam-power. The cylinder is of wood, but is furnished with a number of teeth or cutters attached to its surface parallel with the axis, and projecting about an inch from it. Immediately below the cylinder is a block of wood B, also furnished with cutters, so that when the cylinder revolves its teeth pass very near those of the block, the distance between them being regulated by elevating or depressing the bearings l l, on which the necks of the spindle s s are supported. These bearings are made on two levers l l, which have tenons at their ends fitted into upright mortises made in stout beams bolted to the sides of the engine. The levers l l are movable at one end of each, the other ends being fitted to rise and fall on bolts in the beams as centres. The front one of these levers, or that nearest the cylinder C, can be raised or lowered by turning the handle of the screw; the cylinder is thus made to cut coarser or finer by enlarging or diminishing the space between the two sets of cutters. At one part of the vat is a breasting B', made of boards and covered with sheet lead, curved to the form of the cylinder and nearly in contact with its teeth. An inclined plane I, passes from the bottom of the vat to the top of the breasting which terminates in the block B. The vat is supplied with water from the mill-dam by means of pumps worked by the water-wheel. The water is first discharged by the pipe P, Fig. 4, into the cistern c, the supply being regulated as occasion may require. A grating covered with a hair strainer is fixed across the cistern to prevent any solid impurity from passing into the vat; or the water may be strained through a flannel bag tied over the mouth of the pipe P, as shown in the figure. The vat being full of water and a quantity of rags put in, the cylinder is set in motion, the effect of which is to produce a regular current in the water in the direction of the arrows, by which the rags are drawn between the cutters of the cylinder and the teeth of the block; this cuts them to pieces: they are then thrown over the top of the breasting upon the inclined plane, down which they slowly slide and pass round the partition, and in about twenty minutes are again brought between the teeth of the cylinder and the block. The mode in which the rags are cut will be understood by considering that the teeth of the block are placed somewhat inclined to the axis of the cylinder, while the teeth of the cylinder are parallel to its axis, so that the cutting edges meet at a small angle and pass over each other something like the blade of a pair of shears, and the rags between them are cut up in a similar manner; and as they are brought many times under the action of the cutters, and must necessarily present their fibres each time in different directions, they are reduced to the condition of pulp.
Fig. 5.—BEATING-ENGINE.
The beater, with sixty teeth, and twenty to twenty-four cutters in the block, makes 180,000 cuts per minute, the effect of which is a low musical note or hum, audible at a distance from the mill. In the washing-engine the rags are opened, their fibres separated, and the dirt removed. Any small solid impurities are collected in the trough a, Fig. 4. When first put in the beating-engine, the rags are worked gently, the cylinder is raised some way above the block, so as to rub rather than cut the rags; at the same time a copious stream of water is admitted; after twenty or thirty minutes, the cylinder is let down so as to cut the rags, and the operation is at first so violent that the cylinder is often jerked or heaved up. After three or four hours the engine works steadily; the rags are cut up very small, and form what is called half stuff; this is let out into a basket, which retains it while the water flows off. For some kinds of paper the half stuff is left to mellow, or ferment; but it is usual at this stage to bleach the stuff, which is done by a solution of chloride of lime, in stone vats, or by using this solution instead of water in the engine at the last stage of the washing process, the slides g g being put down in the cover to prevent the loss of the solution. In the course of an hour, the yellow rags or half stuff are converted into a snow white. This is then put into the beating-engine, and in four or five hours it is ground into a fine pulp, a little water being let in from time to time, but none being allowed to escape. The quality of the water has considerable influence on that of the paper; the purest water is of course the best; water from chalky soils introduces lime into the pulp, and this forms a slight incrustation upon the moulds, which is washed off from time to time by vinegar.
In order to prevent common ink from running upon paper, size is introduced at a certain stage of the manufacture; but printing-ink being oily instead of watery, and, moreover, of greater consistence than common ink, is not so liable to run. Hence, for certain printing-papers, the sizing is done in the beating-engine towards the close of the operation. The size consists of finely pounded alum mixed with oil, about a pint and a half of the mixture being thrown into the engine at intervals during the last half hour of the beating. The blue is produced by smalt, or artificial ultramarine.
PAPER-MAKING BY HAND.
When the stuff is properly prepared, it is run out by the pipes o o', Fig. 4, into the stuff-chest, where the different kinds are mixed preparatory to moulding. From this chest it is transferred to vats or tubs, each about five feet in diameter and two and a half feet deep, provided at top with planks inclosed inwards to prevent the stuff from running over during the moulding. Across these planks is a board pierced with holes at one extremity, for supporting the mould. The stuff in the vat is kept at the proper temperature by a small grate placed in a hole lined with copper, at the side of the vat. The fuel is charcoal or coke, or the fire is entirely confined to the other side of the wall, a hole through it being made into the side of the vat. In this way smoke is prevented.
The paper is made into sheets by means of the mould and deckle, Figs. 6, 7. The mould is a square frame, or shallow box of mahogany, covered at the top with wire-cloth; it is an inch or an inch and a half wider than the sheet of paper intended to be made upon it. The wire-cloth of the mould varies in fineness with that of the paper and the nature of the stuff; it consists of a number of parallel wires stretched across a frame very near together, and tied fast through holes in the sides; a few other stronger wires are also placed across at right angles to the former; they are a considerable distance apart, and they are bound to the small wires at the points of intersection by means of fine wire. In several kinds of writing-paper the marks of the wires are evident from the paper being thinner in the parts where the pulp touched the wires. In what is called wove paper, there are no marks of the wires; these are avoided by weaving the wire in a loom into a wire-cloth, which is stretched over the frame of the mould, and being turned down over the sides is fastened by fine wire. The water-mark in paper is produced by wires bent into the shape of the required letter or device, and sewed to the surface of the mould;—it has the effect of making the paper thinner in those places. The old makers employed water-marks of an eccentric kind. Those of Caxton and other early printers were an ox-head and star, a collared dog's head, a crown, a shield, a jug, &c. A fool's cap and bells employed as a water-mark, gave the name to foolscap paper; a postman's horn, such as was formerly in use, gave the name to post paper.
Fig. 6. Fig. 7.