If the design is made well, the various colors can be laid on quite roughly, care being taken merely that each color shall be laid only where it is desired. Then the stone should be permitted to dry, after which all the surplus colors can be scraped away with one manipulation, without danger that one will mix with the other in the design.
V
OIL-PAINTING PRINT THROUGH TRANSFER
Colored impressions resembling oil paintings can be made by printing with colors and several plates on paper grounded with oil color. But perfect oil paintings are produced only as follows:—
Make a considerable quantity of special paper by coating unsized paper thinly with starch-paste or glue. On this make the separate impressions from each color plate. If the painting itself is to be produced from these separate parts, take a canvas that has been prepared for oil painting and lay on it a wetted impression of one of the colors, let us say, red. Print this off under light tension of the press, and when the paper is pulled away, it will be seen that the color has been transferred to the canvas. Then a wet impression of another color is laid carefully in place so that it will register exactly, and the process is repeated, till all the colors have been transferred to the canvas.
The transferring can be done with the hand or with any other method, as no great power is needed, since the color transfers itself readily.
VI
STONE-PAPER
This is the name already generally adopted for a substitute invented by me for the Solenhofen stones.
I had been trying for a long time to invent some stone-like mixture that would be equally suitable for printing. The ordinary parchment of the writing-tablets would do if its surface were not soluble in water. I made considerable progress with a composition of lime and freshly congealed milk after the mixture had aged enough so that the lime could sate itself with oxygen. Then I made a composition of chalk, gypsum, and glue, which I dipped into a solution of nutgall and alum, and I was able to use this for coarser work, at least, if not too many impressions were required.
I did not get a wholly satisfactory idea, however, until I observed that fat spots that were caused on a stone by oil, and also designs that had been transferred to the stone with mere oil color, refused to take color after a few weeks if they were prepared in only the slightest degree.