Spectral Sensitivity of Thermally Modified and Unmodified Wood

The chemical structure of wood changes significantly during thermal modification, significantly influencing the behaviour of wood during weathering. In this study, the effect of different wavelength ranges on thermally modified and unmodified aspen (Populus tremula L.) wood during solar irradiation was investigated. Irradiation was performed by exposing wood to natural solar irradiation under filters transmitting different wavelength ranges. For both woods, the magnitude of characteristic change (discolouration, changes in reflectance, and chemical composition) clearly depended on the solar wavelength bands, but the trends of the changes differed. For unmodified wood, the magnitude of the characteristic changes increased as the portion of short-wavelength radiation in the light increased. However, UV radiation was not found to be the dominant factor influencing changes in thermally modified wood during solar irradiation. The colour and chemical structure of thermally modified wood changed substantially for all studied irradiation conditions