The analysis of tropical wood discoloration caused by simulated sunlight

This study investigated the wood surface discoloration due to simulated sunlight of tropical woods native to South America. Wood of jatoba (Hymenaea courbaril L.), massaranduba (Manilkara bidentata A. Chev.), tigerwood (Astronium graveolens Jacq.), angelim amargoso (Vatairea spp.), angelim pedra (Hymenolobium spp.) and angelim vermellho (Dinizia excelsa Ducke) was exposed to a treatment by xenon-arc lamp light simulating outdoor sunlight, for 144 hours. Colour measurement of exposed and non-exposed areas of samples was performed by means of a spectrophotometer measuring in CIEL ^∗ a ^∗ b ^∗ colour system. The resulting wood discoloration was evaluated according to the value of the overall colour change ΔE ^∗. Changes of particular parameters (L ^∗,a ^∗ and b ^∗) were also observed during exposure. The wood surface darkened rapidly during the first hours of exposure to simulated sunlight. Later, samples showed only a slight increase in lightness. Within one wood species the colour changes were more significant (higher ΔE ^∗) for lighter samples.