FOR BLACK.
Eikonogen, white crystals 6 parts
Water 500 parts
Pulverize the eikonogen, add the water and, at the same time, the material
on its removal from the printing frame, and keep in motion until the
development is effected.
FOR BROWN.
Pyrogallol 5 parts
Water 500 parts
After the development, which requires but a few moments, it suffices to
wash the material to fix the image by eliminating the soluble compounds.
However, for purple the material should be passed in a dilute solution of
tartaric acid and not washed afterwards; it should remain acid.
When it is desirable to obtain an impression in several colors, the
various developers are thickened with starch, then locally applied with a
brush on the image, which is always visible after exposure.
For printing on wood, glass and porcelain, see further on.