Influence of thermal modification on colour of poplar ( populus x euramericana ) rotary cut veneer

Abstract

This paper presents the results of poplar (Populus x euramericana) veneer colour change caused by one-hour long thermal treatments at temperatures of 190, 200, 210 and 215 C. There were three veneer zones included in this experiment: Veneer from sapwood, veneer from heartwood and veneer from intermediate zone - mixed. The measurement results by CIELAB colour system confirmed that there were significant colour differences among the three groups of veneer before thermal treatments. Of all thermal treatments, only the treatment at 210 degrees C contributed to a significant decrease in difference of colour among of all observed veneers. Based on more intensive color change in veneer formats from sapwood, it could be assumed that there were differences in chemical composition between the peripheral and core zones of poplar wood.