Details:
Summary:
After nearly five years of experimental work, a new method has been developed for chemically etching magnesium printing plates. Line engravings which require 60 minutes or more to be etched by conventional means can be etched to 0.020 depth in as little time as five minutes with this new method. The quality of etch is equal to or superior to most conventionally etched plates. Etching of the plate is accomplished by the application of a, unique etching bath in a special etching machine. The bath contains nitric acid and certain organic film forming chemicals which give preferential protection to the sides of the image areas. In effect, the plate is continuously powdered during the etching operation, thereby eliminating the time consuming manual powdering operations. At present, this method of etching is recommended only for line work; however, promising results have been obtained with halftones in the laboratory. It is hoped that this development, by providing an economical engraved printing plate, will help point the way to better and more economical methods of printing.