Wettability of sapwood and heartwood of thermally modified Norway spruce and Scots pine

In this research, the effect of thermal modifications at 170°C, 190°C, 210°C and 230°C on the wettability of sapwood and heartwood of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) was studied by measuring the static contact angles of distilled water on the surfaces as a function of time. The results were compared to industrially kiln-dried reference samples. The thermal modification at the lower temperatures of 170°C and 190°C increased the wettability of all wood materials with the exception of the heartwood of pine that had been thermally modified at 170°C, which was the most water-repellent material in the whole study. Thermal modification at the very high temperature of 230°C was needed to decrease the wettability of wood. The differences in water repellency between sapwood and heartwood were greater for pine than for spruce