PRINTING-PRESS.
INKING-TABLE.
In surface-printing, when types are used, they are packed up closely into masses and wedged together in iron frames, so that they form, as it were, solid blocks; the types or wood-blocks when required to be printed from are placed in the press, and rolled over by a roller smeared with printing-ink—this roller is coated with an elastic substance made of glue and treacle, and resembling India-rubber. It is worked to and fro on the “inking-table” (a smooth iron slab fitted with a receptacle for ink), in order that the ink may be evenly distributed over its surface—a point to which great care and attention, and no little skill, on the part of the workman, is directed. The ink, being rolled over the type, covers and adheres to the surface of the projecting parts. The paper is placed on a frame turning upon a hinge, and is secured in its place by another frame brought down upon it. These frames, with the paper, are now turned down upon the blackened surface of the type, and the whole—paper and type—passed under the printing press, where, by the working of a handle, a piece of iron is caused to descend and press evenly and with great force upon them. On being withdrawn, and the frames opened, the paper is found to have received a perfect impression, in ink, of the type upon which it was impressed. This process, of course, can be repeated to any extent, and as many impressions produced as may be required.
In plate-printing, the plate is first warmed, and all the engraved parts are filled in with ink, the superfluous ink being wiped off, and the surface cleaned bright by using a little whiting (which is rubbed on the hands), leaving only the indented parts full of ink. The paper (in a damp state) is then laid on the plate, with a fold or two of flannel over it, and the whole is carried, by turning the handles of the press, between two rollers, which compress the plate and paper together so forcibly that, when removed, the ink is found to have left the plate and attached itself to the paper, forming an impression.
Printing is now in very many cases done by machinery, worked by steam power, so that a very large number of impressions can be produced in a very short time, as in the case of newspapers, the whole impression of which (amounting to many thousands) is printed in a few hours.
Printing in colors of various tints, so arranged as to form a picture, has lately been much resorted to. The usual method pursued is to print one color, and when that is dry, to print the next, and so on till the picture is complete; but a machine has been invented by which many colors may be printed at one time.
PHOTOGRAPHY.
