Wetting of Tartrate and Arabate Films on Aluminum and Zinc Plates.

The success of the lithographic process depends on the continuous stability of boundaries between the water receptive nonprinting areas and the coplanar ink receptive image areas. As a part of a study on the surface chemistry of lithography, the water receptivity of adsorbed tartrate and arabate films on aluminum and zinc plates was determined from contact angle measurements. The water wettability could be reduced either by an acid hydrolysis product of arabic acid or by the introduction of octanoic acid as a model scumming molecule. The adsorption of arabic acid measured on aluminum and alumina increases markedly with decreasing pH; however, the scumming components are not excluded from the adsorbed film.