Density and density profile changes in birch and spruce caused by thermo-hydro treatment measured by X-ray computed tomography

Birch and spruce samples were scanned using X-ray computed tomography (CT) to determine changes in the density and density profile caused by thermo-hydro treatment (THT). Small-dimension wood blocks were subjected to treatment at three different temperatures (160 °C, 170 °C and 180 °C) for 1 h and scanned before and after treatment. Identical acquisition and analysis procedures were used to evaluate the changes in approximate mean density and radial density profile of oven-dried untreated and treated material. The X-ray CT scans enabled measuring of the changes in wood density after THT. The results confirm that there were similar tendencies in the total density decrease with increasing temperature. However, variations in density changes between the earlywood (EW) and latewood (LW) of birch and spruce were found. A correlation of the radial density profiles of treated versus untreated specimens showed a similar density decrease in EW and LW in birch wood and inconsistent reductions in spruce wood.