DISCOLORATIONS OF HEM-FIR WOOD - A REVIEW OF THE MECHANISMS

The natural appearance of many wood species can be affected by a varie ty of undesirable ''non-microbial'' discolorations. This study reviews and summarizes the current knowledge of the causes of discolorations occurring in western hemlock (Tsuga heterophylla [Raf] Sarg.), and ama bilis ftr (Abies amabilis [Dougl.] Forbes). Recently, such discolorati ons in Canadian hem-fir have become economically important and researc h has been renewed into the cause of this problem, with the intention of proposing preventive measures. Several factors potentially contribu ting to color formation in hem-fir products are addressed. Examples of discolorations found in other wood species are provided to illustrate the significance of such factors.