Polychrome Corporation

Daniel Bourgeois

Jen-chi Huang

An all electrolytic method for quickly and efficiently producing a well roughened, substantially non-directional, fine honeycomb surface on an aluminum sheet which is characterized by excellent adhesion to coatings and therefore suitable for making lithographic printing plates. The method comprises graining said aluminum sheet with alternating current for less than about 10 seconds in a first aqueous electrolyte solution containing hydrochloric acid, washing and drying the resulting grained aluminum sheet, and then further graining said dried aluminum sheet with alternating current for less than about 10 seconds, preferably 5 to 10 seconds, in a second aqueous electrolyte solution containing nitric acid alone or admixed with hydrochloric acid to obtain the substantially non-directional, fine honeycomb surface on said aluminum sheet.

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Mahopac, NY, United States of America

Daniel Bourgeois