Bluestain reduces the value of wood in appearance applications where the natural wood colour is desired. Treatments that remove bluestain without degrading the natural colour of the wood could make this lumber more suitable for appearance-grade applications.
FPInnovations and UBC have each previously developed methods of decolourising bluestain but both resulted in unacceptable colourations in the wood (Binnie et al., 2000; Evans et al., 2007). Follow up work at FPInnovations found that the combination of hypochlorite bleaching and exposure to UV and visible light was able to remove bluestain from lodgepole pine (Stirling and Morris, 2008). The present work identified the minimum treatment times required for effective bluestain removal to be a 10 minute bleaching dip and 10 minutes of exposure to intense light. Near- and mid-infrared spectra indicated changes in surface chemistry after treatment. However, adhesion tests showed no signs of reduced coating adhesion caused by UV damage or hypochlorite exposure.