Combination Plate Etching with the Dow Etch Process.

Since the introduction of the original Dow Etch process for etching magnesium photo engraving sheet more than three years ago, combination plate etching has been a goal toward which considerable research has been directed by Dow, The ANPA Research Institute, Inc. and others. Several procedures have been proposed, tested, and used commercially. Some gave excellent results, but consistency was a problem which was solved only in a few commercial installations. Recently, a new bath was developed which etches coarse screen combination plates. Since the new method uses substantially the same chemicals, but in different proportions, and the same etching machines as the original Dow Etch Line and Halftone processes, the Combination process has gained wide acceptance in a short time.