TWELFTH STONE—DARK RED.
THIRTEENTH STONE—DARK FLESH TINT.
In the case of an ordinary colour-drawing the usual method is to prepare a keystone—that is to say, an outline of the picture, together with the black or grey portions. It is then marked off into colours, each colour requiring, as has been said, a separate stone. Of the uncoloured outline as many copies are printed as there are to be colours in the finished picture, and each of these serves as a key or guide in determining in what position on each stone the separate colour shall be. Each artist then sets to work on his own part of the picture, which is very often, as will be seen by our illustrations, a picture by itself. The master-lithographer knows just how many of these pictures will be necessary to achieve a facsimile. It may be that one colour will frequently have to be printed over another in order to produce the precise effect.
FOURTEENTH STONE—DARK BLUE.
For colour-printing the stone is polished. Naturally the order in which the colours succeed each other is very important, and must be carefully considered. But perhaps the great object of the maker of pictures from stones, after the picture in its various phases has been prepared, is to see that each colour falls accurately into its proper place on the paper. Nothing is more common, in a badly done lithograph, than to find in the face of the human subject, say an attractive young lady, the flesh colour overlapping the collar or the hat, or even extruding itself out into space beyond the ear. All this implies bad "registering." The drawing on each stone must be made to fit in, or register, with the preceding one, so that, as the paper is passed through the printing machine, the picture is built up colour on colour, each, however, being allowed to dry before the next is applied.
In preparing the stone to take the picture extreme care has to be exercised, for so great is its affinity for grease that even a finger-mark will become perpetuated. After a drawing on the stone is finished it is a precaution to coat it with a solution of gum-arabic and nitric acid, which fills up the pores of the stone in the unfilled parts and prevents the drawing from spreading.
