Growth-Quality Evaluation of Black Walnut Wood. Part II-Color Analyses of Veneer Produced on Different Sites

Heartwood color is an important wood quality parameter in the grading of black walnut veneer. One of the primary factors that causes a reduction in veneer grade is variability in heartwood color. This variability may be in the form of streaked heartwood or in coloration not of a uniform light chocolate brown nature. Black walnut trees from four distinctly different sites were selected to describe wood color of commercially prepared veneer sheets, using standard color measurement techniques, so that within-tree, between-tree, and between-site variations could be determined. Selected logs were sliced into veneer by a commercial process and the veneer was graded according to industrial standards. Reflectance data were obtained from selected veneer samples and these data were transformed into standard color parameters. Wide ranges in luminance and purity parameters were obtained. However, only the differences in luminance were detectable upon visual examination. This suggests that variability in luminance (i.e., darkness or lightness) is the primary cause of heartwood color variability. These analyses revealed statistically significant within-site differences in heartwood luminance, but within-tree differences were also observed. Between-site differences were considered less important than within-site differences.