MARBLING
A sponge with large holes is dipped in potash, sulphate of iron, or some other deep coloured dye, and lightly applied over the surface of the leather so that parts of it corresponding to the holes in the sponge are left untouched; or the first application of colour may be made evenly over the leather and the marbling worked, as described, in a second application.
Many varieties of pattern can be obtained by moving the sponge in different ways. Leather may be bought ready marbled by a gelatine process.