Seirogan ingredient. That ingredient in the West may otherwise go by such names as "wood creosote", "beechwood creosote", or "liquid pitch oil", and should be distinguished from industrial "coal-tar creosote". To emphasize the distinction, wood creosote in Japan is sometimes called by such names as and minor variants thereof. The wood creosote is blended with two or more recognized in for their antiseptic and other effects, but the additional ingredients used are different among manufacturers (See under #Chemical composition for a sampling of formulas). Some quarters (perhaps kanpō medicine practitioners and others) insist however that "Seirogan is not strictly speaking kanpō
Wood preservation resistance of wood species is always based on the heartwood (or "truewood"). The sapwood of all timber species should be considered to be non-durable without preservative treatment. Tung oil has been used for hundreds of years in China, where it was used as a preservative for wood ships. The oil penetrates the wood, and then hardens to form an impermeable hydrophobic layer up to 5 mm into the wood. As a preservative it is effective for exterior work above and below ground, but the thin layer makes it less useful in practice. It is not available as a pressure treatment.