Meta-analysis of chromatic properties of heat-treated wood

An attractive darker colour is an important advantage of heat-treated wood. The variation in colour of the heat-treated wood is influenced by the heterogeneous structure of wood and the different technologies that can be applied. In this study, chromatic parameters ( L * , a * , b * and △ E * ) were investigated via meta-analysis. The colour of heat-treated wood was species-dependent and associated with the tree age, silviculture method, and wood characteristics (hardwood or softwood, heartwood or sapwood, etc.). With increasing wood density, L * and b * decreased, while △ E * increased. In addition, the colour change of heat-treated wood was closely related to treatment factors (time, temperature, agent of treatment). 180 °C was a critical temperature for the evolution of colour changes. Predictions of colour changes were performed by fitting the chromatic parameters with density, treatment time, and temperature. Prediction of the colour of heat-treated wood was feasible based on the results of the meta-analysis. This study showed the quantitative influences of the material and technology related factors on the chromatic properties of heat-treated wood, and the results are helpful for regulating and optimizing heat treatment technology.