Measurement of photodegradation-caused roughness of wood using a new optical method

• Wood samples were irradiated by mercury vapour lamp at 80 °C.
• The effect of photodegradation on surface roughness of wood was studied.
• The diffuse reflectance IR spectra were recorded.
• The baseline shift was found to monitor the roughness change caused by the photodegradation.
• The method was sensitive to measure small changes.

The aim of this study was to clarify the intensity of the surface roughening of wood caused by light radiation using a fast optical method. The samples were irradiated by mercury lamp and the roughness change was monitored traditionally using a perthometer. The infrared (IR) diffuse reflectance spectrum was measured and the baseline shift was found to be a proper parameter to monitor the roughening effect of photodegradation. Linear correlation was found between the traditionally measured roughness and the baseline shift. This newly developed optical method is able to detect the degradation difference between earlywood and latewood. Some of the samples were immersed in distilled water for a day after an all light irradiation period of two days. This new baseline shift method was able to visualise and determine the small change in roughness caused by the leaching effect of water.