Wood photosensitivity to different artificial light sources

Mostly the effect of solar and UV radiation on wood photodegradation has been researched. This paper discusses the effect of artificial light sources, which differ in the spectral composition of the emitted light, on the photodegradation of wood. Ash, birch, aspen, pine sapwood and heartwood, and spruce wood were exposed to two LEDs of different colour temperature (3000 and 6500 K), incandescent and fluorescent lamps. Changes in colour (ΔE) and colour parameters L*, a*, b* (CIELAB colour space) as well as reflectance and FTIR spectra were analysed to evaluate the photodegradation of wood depending on the light source. According to the results of changes in the chromaticity system of woods, the tested light sources can be divided into two groups: one group with similar results includes the two tested LEDs while the other group includes incandescent and fluorescent lamps. Lower irradiation dose was needed for the LEDs to impart visually perceptible discolouration, whereas colour changes of greater magnitude were caused by the incandescent and fluorescent lamps at higher irradiation doses. It was detected that depending on the light source, there are differences in the changes in the chromophores between hardwoods and softwoods, with more total discolouration observed for softwoods. The transformations in the chemical structure, which was analysed by FTIR, considerably differed for all tested light sources with a general trend of the greatest effect of the fluorescent lamps followed by the incandescent lamps and LEDs.