The mould is then returned to the vat-man, who repeats the process as before: the coucher, in the mean time, lay3 another felt upon the sheet or tablet just couched, whereon the second sheet is to be laid in the same manner, and so on until all the felts are occupied; over which another level plank is placed, and the whole drawn away on a small rail-road waggon to the great press, where it undergoes a pretty severe pressure.
The tablets will now be found to have sufficient adhesion to bear handling with care, and are separated from the felts, and placed one upon another, so as to form the packs; these packs are to be submitted again to the action of the press, until more water is expelled; then are parted sheet by sheet, pressed and parted again; and this is repeated as often as is necessary, taking care to increase the pressure every operation, until the face of the tablets is sufficiently smooth; they are then carefully dried, sized, picked, sorted, etc.; carried to the rolling mill, and several times passed between the polished cylinders, to give them the last finish.
The above is the process for the plain or white tablets. In making the tinted tablets, the following additional particulars are to be attended to. The rags are cleansed, washed, and beaten into half stuff", in the usual way; the water being drained off the pulp is put into a vat with a solution in water of acetate of alumine, or sulphate of iron, as a mordant or ground to fix the colour intended to be made; the whole is well incorporated, and suffered to remain for half an hour or more, when the colouring tincture, previously prepared, is added; after which, the whole being returned to the engines, is beaten into fine pulp, and then wrought into fine tablets. The dyeing materials chiefly made use of by Mr. Steart, are, mangrove bark, quercitron bark, best blue Aleppo galls, sulphate of iron, and acetate of alumine. A due combination of these materials produce a great variety of drabs, greys, sand-colours, etc.
An apparatus and process for sizing paper in a more effectual manner than it had previously been done, was recently patented by Mr. Towgood, of Dart-ford, in conjunction with Mr. L. Smith, of Paternoster-row, London. This invention consists in the application of pressure along with the size; which is effected by depositing on the surface of a pair of pressure rollers, or on one of them, if the paper be required to be sized only on one side, a thin uniform film of size, which is pressed into the paper as it passes between the rollers. An endless felt is sometimes made to pass over each of the rollers, and in that case the size will be forced through the felt to the paper. This sizing apparatus may be applied either separately, or in combination with a paper machine of any construction; but the form and arrangement of the different applications will necessarily vary with the form of the machinery to which it is applied. The form represented in the following diagram will be sufficiently explanatory.
a b represent two pressure rollers, with pieces of endless felts ccc, and ddd passing around them, being supported and guided by a series of friction rollers e e e and fff; g is a small trough with a perforated bottom for supplying the surface on the surface of the pressure roller a; and A is a similar trough for supplying size to the roller i, which transfers its supply to the other pressure roller b; and jj are two scrapers for keeping clean the surfaces of the pressure rollers.
The cutting of paper into sheets of any required dimensions as exactly and expeditiously as possible, is an object of great importance to the manufacturer; and as the machine-made paper is of considerable greater width than is required, it becomes necessary to cut it lengthwise. The following is the patented method adopted by Mr. Crompton, of Tamworth, in Lancashire, and Mr. Taylor, of Marsden, in Yorkshire, according to their enrolled specification, dated 1828. Fig. 1 is a side elevation of the machine; Fig. 2 a plan of the cutters. a is the roller upon which the paper (either in the moist state in which it is delivered from the felts when freshly made, or when dry,) is rolled; b b and c c are two pairs of drawing rollers, which conduct the paper first between the circular cutters ee, and thence on to the roller d, where it is wound in its divided state. The shaft upon which the upper cutter is fixed, is driven by any prime mover; and by means of endless bands and pulleys it imparts motion to the upper drawing rollers b and c; these two upper rollers turn the two lower, by means of cogwheels at the other extremities of their axes, which gear into each other the vol.
K K upper cutter has in like manner a toothed wheel upon its axis, which turns another toothed wheel upon the axis of the lower; none of these toothed wheels are brought into view in the drawing, to prevent confusion. By the revolutions of these parts of the apparatus, the paper, represented by a line gg, is drawn from a between the rollers b, is severed at e, and thence is carried by the rollers c on to d, by means of an endless band from the latter, as shown. In order to accommodate this movement to the increasing circumference of the roller d, occasioned by the paper accumulating upon it, the band pulley on d is a friction roller, which is set so as to allow of its slipping a little in its revolutions. It should also be noticed, that the axis of the lower cutter is not quite parallel to the axis of the upper one, by which means the edges of the cutters facing the rollers a are brought into contact, whilst the other edges diverge, which causes the paper to be more freely delivered from the cutters.
The great rapidity of this process of cutting is evident.