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Thermal modification is the most important commercial modification procedure. Thermally modified (TM) wood has improved durability, but its performance does not meet expectations predominately under moist conditions. To reduce water uptake of TM wood, Norway spruce specimens were treated with suspensions of a natural wax by dipping impregnation (DipI) or by vacuum-pressure impregnation (VPI). Wax-treated specimens were subsequently TM at 185, 200, 215, and 230°C. Control specimens were heated up to 100°C only. Contact angle (CA), short-term and long-term water uptake, bending strength, and performance against wood decay fungi of the resulting material were determined. The results show that a combination of wax treatment and thermal modification have a synergistic effect that considerably improves hydrophobicity, reduces liquid water uptake, slows down water vapor uptake, and improves the resistance against fungal decay of the treated material. [ABSTRACT FROM AUTHOR]

Sweet chestnut ( Castanea sativa ) heartwood is one of the most durable European commercial wood species. Various aspects that could potentially influence the durability were studied in the present research: presence of extractives, ring width and weathering. The properties of wood that had been in outdoor use for 35 years were also examined. The results indicate that ring width and weathering (outdoor use) did not influence the durability. None of the fungi used were able to degrade sweet chestnut heartwood in a modified EN 113 experiment. After extraction with methanol or water, specimens lost between 11% and 15% of total mass by leaching of extractives. However, extraction only slightly decreased the durability of the leached wood. This indicates that other components (in addition to water and methanol soluble extractives) could be responsible for durability. Furthermore, analysis of 35-year-old wood showed that not all relevant properties of the old sweet chestnut wood deteriorated within the mentioned time frame. This proves that old sweet chestnut hardwood can potentially be reused for a variety of applications. [ABSTRACT FROM AUTHOR]