The Study of Spot Scumming Generating Mechanism on Lithographic Printing Plate

Abstract

In order to develop a high-quality and easy printing plate material, it is important to understand the printing phenomena. In this study, we could evince the mechanism of spot scumming (= machine stop greasing) generation. The more the chloride ions mix under the printing condition, the more spot scumming is generated. By morphological observations, we found that the spot scumming generated surface of a lithographic printing aluminum support is not different from the clean surface, but under an anodized aluminum film, the inner aluminum is dissolved by the chloride ion. Moreover, by electrochemical analysis, we found that the ink consumes the electron generated by aluminum solving via an oxidative polymerization mechanism. We suggest that the oxidation-reduction reaction between the ink and aluminum promotes oxidation polymerization of ink, generating spot scumming.