The influence of thermal treatment on color response of wood materials

In this study, the influence of thermal treatment on color changes of six different wood materials was investigated. Test specimens were subjected to three different temperatures (160, 180, and 200 degrees C) and durations (3, 5, and 7 h). The data obtained were analyzed using variance analysis, and then the statistical analysis of Tukey's test was conducted. After this treatment, the results showed that the color values of the six wood materials changed significantly. It was determined that L* (lightness) values decreased; the minimum change in L* was similar to 4% for Juniper wood, and the maximum change in L* was similar to 64% for Beech wood. The values of a* (red coordinate) and b* (yellow coordinate) showed varying levels of increase when the heat treatment conditions were 160 degrees C for 3 to 7 h (not including Cherry wood), but the values began to decrease slowly after treatment at 160 degrees C for 5 h. The ratios of the minimum and maximum color change in a* and b* were determined at 180 degrees C for 3 h in Plane wood, 200 degrees C for 5 h in Hazelnut wood, and 160 degrees C for 3 h and 200 degrees C for 7 h in Beech wood. As temperature and duration were increased, the minimum total color change (Delta E Delta ab*) was similar to 3.5% for 160 degrees C at 3 h in Cypress wood, and the maximum total color change (Delta E?ab*) was similar to 50% for 200 degrees C at 7 h in Cypress wood. (c) 2010 Wiley Periodicals, Inc. Col Res Appl, 2012; Published online 2 December 2010 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/col.20655