The Effect of Solar Radiation on the Surface Checking of Wood

IRG/WP 07-40356

P Evans, K Urban

The aim of this research was to investigate whether exposure to solar radiation increases the checking of wood exposed to the weather, and examine the causes and spectral dependency of such an effect. Lodgepole pine samples were exposed outdoors under filters which transmitted selected regions of the solar spectrum while allowing other weathering factors to act on samples. Surface checking in samples was quantified after 12, 24 and 36 weeks, and the structural changes occurring at weathered wood surfaces were examined. Check numbers and dimensions were greater in samples exposed to the full solar spectrum than in samples exposed under filters that blocked the transmission of UV, visible or infra-red radiation. Samples that were shielded from more energetic wavelengths developed less checking. Checks developed in the rays and propagated at the interface between adjacent tracheids, close to the middle lamella. We conclude that exposure to UV and visible light increases the tendency of wood to check during exterior exposure. Our findings suggest that water-repellent treatments designed to prevent wood exposed outdoors from checking should contain additives that restrict the surface photodegradation of wood.


Keywords: solar radiation, checking, surface, weathering, pine

Conference: 07-05-20/24 Jackson, USA


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