The effects of several commercial wood coatings on the deterioration of biological pigments in wood exposed to UV light

This research subjected four wood species pigmented with the red stain of Scytalidium cuboideum and Acer negundo wood pigmented with the tree’s naturally occurring red stain to natural and artificial UV light. Several commercially available coatings were applied to determine the effect of coating on the degradation of both red stains over time. The red stain of Acer negundo was found to be significantly less stable in UV light than the red pigment produced by S. cuboideum on any wood species, even A. negundo. None of the tested coatings significantly increased the pigment retention time of the red stain produced by A. negundo. The red stain of S. cuboideum was significantly affected by both coating and wood species; Populus tremuloides retained pigment significantly longer than Fagus grandifolia or Acer saccharum, and the Danish oil coating retained pigment significantly longer than the lacquer, water-based polyurethane with UV inhibitors, or the uncoated samples. Overall, lacquer increased the degradation rate of the red pigment produced by S. cuboideum, with the most pronounced increase occurring on F. grandifolia. These results indicate that the red-pigmented wood produced by A. negundo may not be appropriate for applications involving UV exposure, regardless of coating utilized. However, P. tremuloides wood pigmented with S. cuboideum may be appropriate for such applications, especially if Danish oil is applied as a coating.