Colored lithography, called chromo-lithography, is produced by using several stones consecutively (each transferring a separate color), so that the design shall be complete when the whole are printed.
The art of printing consists in producing impressions from a pattern or types--cut out and projecting, or engraved and indented--by smearing the projecting parts or filling up the indented markings with ink, so that impressions, to any number, and exactly resembling each other, may be taken from them. Printing is comparatively a modern invention, although impressing or taking impressions from seals is one of the very oldest. It is divided into two kinds, plate-printing and surface-printing. Printing from type or blocks having the marks to be impressed raised, is called surface-printing, while that in which the lines or marks are cut in, is called plate-printing.
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 On being withdrawn, and the frames opened, the paper is found to have received a perfect impression, in ink, of the type upon which it was impressed.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.