Zinc-Etch'ing, a favorite process for reproducing pen-drawings or engravings in white and black. A photograph is taken of the drawing or engraving which is to be copied, and the negative is placed over a zinc or copper plate, which has been covered with a varnish, and is then exposed to the light. The varnished portions which are exposed to the light become insoluble, while the parts protected by the lines of the photograph remain soluble. The plate is then treated with an acid solution by which the soluble portions of the varnish are removed and the lines of the drawing or engraving are etched or eaten into the metal. Consult Hamerton's Etcher's Handbook Herkomer's Etching and Kohler's Etching.