Powderless Etching of Copper.

A process for the powderless etching of copper plates for photoengraving has been developed, based on the formation of a protective film on the metal surface by reaction between copper ions and an organic additive to the ferric chloride etchant. Two additive materials, GT-1 and PERl 13a are available for use by members of Photo- Engravers Research, Inc. Careful control of bath composition, bath temperature and machine speed is needed. Powderless etched plates have proved superior to plates prepared conventionally in efficiency of plate production, in subsurface structure, and in tone reproduction.