Wettability of extracted southern pine

Southern yellow pine wood blocks were sequentially extracted with ethanol-toluene, ethanol, and water. The contact angle of unextracted and extracted wood blocks was measured using water as a reference liquid. Wood extracted with ethanol-toluene exhibited higher contact angles compared to unextracted samples, suggesting a partial coverage of the wood surface by hydrophobic wood extractives. The same observation was noticed after the second extraction with ethanol. A third sequential extraction with water resulted in a contact angle similar to that of unextracted wood, indicating the solubilization or removal of extractives by water.