COLORS OF KNOTS IN SOFTWOOD LUMBER

The colors of knots appearing on planed lumber from seven softwood species were measured with the L*a*b* colorimetric system. Recognition by the color differences between knots and the surrounding wood tissues have been studied. In most species the colors of knots differ from the surrounding wood, but the extents and features vary among the species. The differences of color between knots and the surrounding wood is the most significant in hinoki, followed by akamatsu and white fir. Sugi, lodgepole pine, and Douglas-fir show less significant differences. Knot color of karamatsu is similar to the color of the heartwood, particularly of the latewood. This indicates that knots of karamatsu cannot be recognized by color from the clear parts of lumber.