Acetylation of wood causes photobleaching.

This paper deals with the photobleaching of acetylated wood. The acetylated spruce wood was irradiated by artificial sunlight emitted from xenon lamp with covering several kinds of band-pass filter. The lightness (L()) of acetylated wood increased with integral irradiance. The chroma (ΔC()) decreased by light-irradiation with wavelength from 430nm to 500nm. However, the light-irradiation including ultraviolet ray region made it decrease after increase with integral irradiance. The visible light made hue angle (h°) increase, however, the ultraviolet ray made it decrease. The lignin degradation and the production of carbonyl groups were observed by light-irradiation including ultraviolet ray. However, no remarkable changes in IR spectra were observed by visible light-irradiation. Photobleaching of acetylated wood was caused by mainly visible light without modifying the IR spectra of lignin.