PHOTORESISTANCE OF HEAT TREATED WOOD IN INTERIOR USE

Wood is photochemical unstable substrate witch change colour even in interior use because of photooxidation of lignin. In this study, an attempt was made to analyze surface discolouration of heat treated wood when exposed to UV radiation filtered through window glass. The colour change was measured using a spectrophotometer on heat treated samples of beech and ash which were uncoated and coated with three different varnishes. The samples were exposed 32 days using QUV tester equipped with UVA-351 lamps. The experiment shows that the trend of discolouration could be observed on the all samples tested according to the overall changes in colour (Delta E*) after 32 days of exposure. The greatest discolouration, according to Delta E* values were recorded for uncoated samples and samples coated with UV-cure water borne varnish. The 2k PU varnish had reduced discoloration of wood, and adding the UV-absorber to this varnish did not improve its colour stability.