Minute Color Measurement of Sugi Timber (Cryptomeria japonica) Dried by Five Conditions II.

Warm color of wood is a very important design factor for building materials, furniture, and so on. Therefore, color measurements for the surfaces of timber and wood products are often performed using a colorimeter. However, most of such color data are mean values inside a confined measurement area, and these values are entirely compared and evaluated based on L, a, b and ΔE values. In the present study, surface colors of sugi timbers (Cryptomeria japonica) dried by five different conditions were measured using an imaging spectrometer, and surface colors of 4 parts (heartwood-latewood, heartwood-earlywood, sapwood-latewood, and sapwood-earlywood) were examined for each drying condition based on the three color attributes (lightness L, chroma C, and hue angle H °). The color analysis revealed very clear linear relations between H ° and L regardless of drying conditions. Although the surface colors of the 4 parts were clearly distinguished from each other in the air-drying condition, the range of hue angle became narrow as the drying conditions became more severe and it was difficult to distinguish the two parts of heartwood-earlywood and sapwood-latewood by their colors. Originally bright surfaces such as the sapwood-earlywood part selectively darkened (lower lightness) and deepened (higher chroma) by the kiln drying.