Process for electrograining aluminum substrates for lithographic printing

Abstract From the Canadian patent

Abstract of the Disclosure, Aluminum substrates are electrograined for lithographic printing in an electrolytic cell using an electrolyte of hydrochloric acid or nitric acid, and a "regulated alternating current" whereby the inter-electrode voltage is applied with a higher anodic voltage than the cathodic voltage the ratio, of cathodic coulombic input to anodic coulombic input is less than one and preferably in the range of 0.3-0.8 and the, anodic half cycle period or time is not longer than the cathodic half cycle period or time, so that they acquire a "pits-within-a-pit" grain structure uniformly over their entire surfaces.