Degradation of Japanese Lacquer under Wavelength Sensitivity of Light Radiation

Degradation of Japanese lacquer caused by light irradiation was examined at various wavelengths. By exposing lac-quer specimens to a narrow monochromatic light band isolated from dispersed polychromatic light emitted by a Xe lamp source, the wavelength sensitivity characteristics of lacquer degradation could be determined on the basis of ra-diant energy. Tame-Urushi (brown) lacquer displayed peak degradation maxima at 220 and 315 nm. A broad shoulder peak was also observed in UVA. For Shu-Urushi (cinnabar) lacquer, in addition to peaks in the UVA-UVB range, a large degree of degradation was observed following exposure to light in the visible range. Ao-Urushi (green) lacquer showed similar characteristics, although it was less prone to degradation. Similarly, Shin-Urushi (black) lacquer showed little change in response to light, although UV light caused limited degradation. These results indicate that along with the damage caused by UVA and UVB, visible light in the range 510- 650 nm may also have a significant degradation effect. Our results provide experimental evidence that Japanese lacquer responds differently to light of various wavelengths and that specific wavelengths, including visible light, can cause significant degradation