Effect of Heat Treatment Temperature on the Color of Okan Wood

In this study the effect of high temperature on color change of okan wood was investigated. Wood specimens were subjected to heat treatment at 160°C, 180°C,200°C,220°Cfor 4 hours with the superheated steam as a heating medium and a shielding gas. Color changes were measured in the Minolta Croma-Meter CR-300 color system. The color parameters L*, a*, b* were determined by the CIEL*a*b* method on the surface of untreated and treated wood, and their variation with regard to the treatment (△L*,△a*,△b* ) were calculated. It was found that heat treatment resulted in a darkening of wood tissues, Color became dark with the temperature increases. The darkening accelerated when treatment temperature exceeded approximately 200°C. We found that heat treatment temperature were substantially important regarding the color responses. Strong correlations between total color difference and the treatment temperature were found. The effect of treatment temperature on color change in sapwood is more obvious than that in heartwood, the color of sapwood and heartwood tended to be more uniform when the temperature reaches more than 200°C.