Japanese lacquer is called “Urushi” in Japanese. Urushi have meanings such as Urushi tree, its resin and also Urushi crafts. Urushi has been used 9000 years ago in Japan. In this long history, Urushi crafts techniques have been developed, refined and inherited by many Urushi craftspeople. As a result, Urushi affect Japanese culture and aesthetic feeling greatly.
Urushi has various characteristics. For example, Urushi coating surface is very smooth and glossy. And more, Urushi is strong to acid and alkali. However it is very weak to ultraviolet rays. As a result, Urushi coating is degraded very quickly in sunlight.
In this study, 6 specimens were prepared by painting 6 kinds of Urushi resins on PMMA (polymethylmethacrylate) boards. Weathering tests of these 6 specimens were done to clarify the degradation of Urushi coating. Additionally, L* value (Brightness), C* value (Chroma) were also measured by spectrophotometric colorimeter to investigate the influence of the degradation on the optical characteristics. Both L* value and C* value were increased after weathering test in most specimens. Glossiness values of specimens were measured by gloss checker. As a result, glossiness values were decreased after weathering test in most specimens.
There was a difference in advance of degradation according to the kind of Urushi. Then when Urushi is used, there are necessities of proper use and change of refining method for Urushi.