Wood of the Month:
Blackbean's a Winning Veneer Entry From Down Under

By Jo-Ann Kaiser


FAMILY NAME
Castanospermum australe of the Family Leguminosae

COMMON NAMES
Blackbean, Moreton Bay bean, Moreton Bay chestnut, beantree, yuba, bean wood

HEIGHT/WEIGHT
Average height is 130 feet with diameters of 4 feet. Average weight is 44 pounds per cubic foot with a specific gravity of 0.70.

PROPERTIES
Experts say extreme care is needed to dry the hard and heavy wood of blackbean. They recommend very slow air drying prior to kiln drying to avoid splitting and honeycombing. Wood contains minerals that can pose problems during machining. Wood is moderately heavy and tough with low stiffness and shock resistance and moderate movement in service. Wood is brittle and not recommended for steam bending.

Blackbean, a tree from Australia also known as beantree, is named for the tree's distinctive looking fruit, found in large woody pods. The pods are brown-colored on the tree but turn black after they age and fall. The seeds are poisonous, but legend has it that the Aborigines once found a way to treat and prepare the blackbean seeds. They supposedly soaked and washed the cracked seeds repeatedly and ground them into meal, which was fashioned into cakes and roasted. The seeds reportedly tasted a little like chestnuts, which accounts for one of its common names, Moreton Bay chestnut.

Today blackbean is known for its attractive veneer and heavy, tough lumber high in decay resistance. Its use as a foodstuff is a thing of the past. Common names for the tree - Moreton Bay chestnut and Moreton Bay bean - refer to the area near Brisbane where the tree was reportedly first discovered. Blackbean flourishes in the moist forest regions of Eastern Australia, specifically from Queensland to New South Wales.

Beautiful But Not Widely Used
Greg Engle, sales manager for Certainly Wood, East Aurora, NY, is familiar with blackbean veneer, but says his company has not had many requests for it in the last four to five years, probably because it is less available than other veneers. "When we see it, it is usually quarter cut. It's a beautiful veneer, especially when you find an interesting figure, like a mottle figure typically. Blackbean is usually used for high-end custom furniture and elevator interiors. When it is finished properly, it's a very lustrous wood," Engle says.

In addition to the uses mentioned, blackbean is used for fancy turnery, brushbacks, tool handles and mallet heads. Sculptors and turners like the properties and look of blackbean and prize blocks with interesting grain patterns.

Blackbean also is used for more utilitarian uses such as heavy construction and interior joinery in the areas where it grows. Because of the wood's unique insulating qualities, it is used for electrical appliances, switchboards, electrical fittings and measuring instruments.

The veneer is used in many upscale uses including architectural paneling and flush doors and is also popular for marquetry and inlay work.

Striking Good Looks
Blackbean's heartwood is dark, usually chocolate brown, with narrow steaks of black or grey-brown. The streaks are actually parenchyma tissue and surround large pores in the wood. The wood is usually straight-grained but can have an interlocked grain that yields an attractive striped figure when quarter cut.

Albert Constantine Jr., who refers to the tree as yuba in his book, Know Your Woods, describes blackbean wood as "attractive in appearance, brown or olive green in color deepening nearly to a black with streaks of lighter shades, like a blending of chestnut and teak."

Working properties earn mixed reviews with this wood. The wood poses no problems for nailing and screwing. The heartwood is moderately resistant to termite attack but the sapwood is susceptible to powder post infestation. Blackbean lumber is rated as durable.

Drying can be a problem and material should be air dried slowly before it is kiln dried or the wood will split or honeycomb. Experts recommend keeping cutting tools very sharp. According to author William A. Lincoln, in the book World Woods in Color, "The wood has a high resistance to the cutting edges of tools and a moderate blunting effect. The relatively softer patches of lighter colored tissue tends to crumble during planing or moulding unless tools are kept very sharp." The wood has minerals and gum pockets plus a "greasy feel" that interferes with machining, gluing and finishing.

Still, all references to blackbean include high praise for the beauty of the wood and veneer despite problems with availability and working the wood.

                                                                                                                                                                                           

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