Plasma treatment and bleaching to remove blue-stain from lodgepole pine sapwood

Abstract

The hypothesis that a combination of plasma treatment and bleaching will be more effective than bleaching alone at removing stain from blue-stained lodgepole pine sapwood was tested. Blue-stained wood was pre-treated with glow-discharge plasma in vacuo for different times, immersed in a concentrated aqueous solution of sodium hypochlorite for 30 s and air-dried. The colour of dry samples before and after plasma treatment and also after bleaching was measured with a spectrophotometer. Prolonged plasma treatment (without bleaching) removed some blue-stain, but the effect was small. In contrast, the combination of plasma treatment and bleaching removed most of the blue-stain. It was concluded that vacuum plasma pre-treatment and bleaching shows promise as a way of removing blue-stain. Further research should be done to examine whether more practical (atmospheric) plasma pre-treatments can increase the effectiveness of hypochlorite bleach at removing blue-stain.