Yellow balau is a wood used by structural engineers due to its high tensile strength. It is commonly used for boats, bridges, staircases, door and window frames, heavy traffic flooring, vehicle bodies, cabinets and heavy duty furniture. Yellow balau is indigenous to Malaysia, India, Indonesia, Vietnam, Pakistan, Laos, the Phillipines, Thailand, Burma and Cambodia. Its capacity to dry slowly is a benefit in woodworking providing for efficient re-sawing before the final product is made.
Yellow balau wood gets its name from its yellow-brown appearance. During growth, the first layer of balau wood, the heartwood, is either yellow or has a greyish brown hue. The sapwood or outer layer of balau wood is a lighter yellow. After long-term exposure to air and water, the outer layer of yellow balau wood will change colour and look silver or grey. When the heartwood is exposed to air and water, it turns from yellow or grey to a deep brown or olive colour.
Strength and Longevity
Yellow balau wood is both weather and pest resistant. It is reported to be 50 per cent stronger than oak. Three tested species of yellow balau have a tensile strength of at least 12 megapascals when green and first cut. The wood takes a long time to dry after being cut. Once dry, shear strength increases by 25 per cent. Strength contributes to the longevity of yellow balau. Untreated specimens of balau species, Shorea maxwelliana, was found to have the longest tested lifespan of 15.8 years when used in a graveyard. Yellow balau is resistant to preservative treatments and does not necessarily last longer than untreated wood.
The toughness of yellow balau wood makes it very difficult to cross cut. The Shorum laevis species, however, provides for easy cross cutting when freshly cut or considered to be green. Planing or flattening and smoothing the wood out is fairly easy for most species when they are newly cut except for Shorum maxwelliana. Once dry, planing becomes difficult. Boring holes in the wood to impart joints should also be done while the wood is green. Because of these machining properties, it is best to begin woodworking with yellow balau before it dries.
Yellow balau tends to develop fissures in the surface of the wood while it dries because it dries slowly. While the heartwood is resistant to infestations and infections, the outer sapwood is prone to fungus and powder-post beetle takeovers. When choosing yellow balau for construction support, very old trees should be avoided as the heartwood may be soft inside and filled with pockets of resin. Soft heartwood can result in compression failures. Further, even if most of the heartwood appears stable in an old tree, there may be stretches of wood next to the heartwood that are full of soft intercellular canals.