When the intention is to print from the stone, it is placed upon the platten or bed of the press, and a proper sized seraper is adjusted to the surface of the stone. Rain water is then sprinkled over the gum on the stone, which, being dissolved gradually, and a wet sponge passed lightly over all, the printer works the ink, which is on the colour table placed beside him, with the roller, in all directions, until it is equally and thinly spread on the roller. The roller is then passed over the whole stone, care being taken that the whole drawing receives a due portion of ink; and this must be done, by giving the roller an equal motion and pressure, which will of course require to be increased, if the drawing does not receive the ink readily. When the drawing is first used, it will not receive the ink so readily as it will afterwards; and it is frequently necessary to wet the stone, and roll it several times, before it will take the ink easily. After this takes place, care must be taken not to wet the stone too much; the dampness should not be more than is necessary to prevent the ink adhering to the stone where there is no drawing. After the drawing is thus rolled on, the sheet of paper is placed on the stone, and the impression taken.
Upon taking the paper off the stone, the latter appears to be quite dry, owing to the paper having absorbed the moisture on the surface; it must therefore be wetted with a sponge, and again rolled with ink, the roller having been well worked on the colour table before being applied. During the printing, some gum must always remain on the stone, although it will not be visible, otherwise the ink will be received on the stone as well as on the drawing, by which the latter would be spoiled; so that if by too much wetting, or by rubbing too hard with the sponge, the gum is entirely removed, some fresh gum water must be laid on. If the stone has in the fust instance been laid by with too small a quantity of gum, and the ink stains the stone on being first applied to it, gum water must be used to damp the stone, instead of pure water. Sometimes, however, this may arise from the printing ink being too thin, as will afterwards appear. If some spots on the stone take the printing ink, notwithstanding the above precautions, some strong acid must be applied to them with a brush, and after this is washed off, a little gum water is dropped in the place. A steel point is here frequently necessary to take off the spots of ink.
The edges of the stone are very apt to get soiled, and generally require te be washed with an old sponge after rolling in; they must also frequently have an application of acid and gum, and sometimes must be rubbed with pumice-stone. If an ink is too thin, and formed of a varnish not sufficiently burned, it will soil the stone, notwithstanding the proper precautions are taken of wet ting the stone, and preparing it properly with acid and gum; and if, on the other hand, the ink is too thick, it will tear the lighter tints of the chalk from the stone, and thus destroy the drawing. The consideration of these circumstance leads at once to the - . , .