Effects of Curing Conditions on Color of OrientalLacquer Film with Pigment

Abstract

In the manufacturing processes for lacquer wares, a color conflict between a raw lacquer solution mixed withpigments and resulting oriental lacquer coatings often becomes a problem. This can be attributed to stronglydark brawn color of the original lacquer solution. In this paper, effects of curing conditions, UV irradiation andconventional enzymatic laccase oxidation at room temperature, of the lacquer coatings on their color aftercuring are investigated. As a result, curing by UV provided clearer colors of a lacquer film as compared to theconventional curing. Furthermore, an addition effect of acid or base into the lacquer solution is also examinedwith the conventional curing process. When a lacquer coating was cured by an ordinary enzyme together withacid or base additives under certain humidity, the coating with acid condition showed stronger colors thanthe ones with base. This demonstrates that acidic reagents should be added in the coating solution in order toobtain the desired color of lacquer wares rather than basic reagents. Finally, the component which leads thesecolor changes were estimated by GC/MS analysis and they indicated that condensed catechol compounds areconsidered to be actual color changing agents.