Color stability of heat-treated wood during artificial weathering

The color change of wood after exposure to UV light may produce aesthetical damages. The stability of the color to light exposure is an important issue. This study describes experiments of testing the color stability of heat-treated wood samples. Heat treatment was done at 240 degreesC during 2 hours, under nitrogen. Heat-treated samples of ash, beech, maritime pine and poplar heartwood were exposed to UV-Iight (QUV equipped with fluorescent lamps UVA-340) during 835 hours. Color measurements during accelerated weathering were made at intervals throughout the test period. The results are presented in DeltaE and L* a* b* coordinates according to the CIELab system. The experiments show that the color stability for heat-treated wood is better during the 835 hours of exposure when compared to untreated wood. The properties of heat treated wood (lignin modifications, and monomers of phenolic compounds) are probably involved in the retified wood resistance against UV light under experimental conditions.