Wenge highly favored, but endangered
By Gene Wengert
June 17, 2013 | 9:00 am CDT
Wenge (Millettia laurentii) is a tree found mainly in Tanzania and Mozambique. Another name for the wood is African rosewood. The tree is short, seldom reaching over 50 feet in height. The diameter of the mature tree is 30 to 36 inches. The bark has been valued for a reddish sap called kino. Kino is high in tannin content and is very astringent. Note: A very close relative in appearance and strength is panga panga (Millettia stuhlamnnii).
The wood is very heavy and can be used as a substitute for hickory in sporting goods where its high impact resistance is a plus. In fact, its striking grain pattern, especially when quartersawn (photo) makes it more attractive than hickory. Wenge also is used for both strip and parquet flooring, especially as an accent with a lighter colored floor. It is also used as an accent wood for furniture and cabinets. It has been used for guitar fingerboards. Although not common in the North American markets, wenge lumber is sometimes available. The species is now considered to be endangered.
Processing suggestions and characteristics
Density. The density of kiln-dried wood ranges from 45 to 55 pounds per cubic foot. A board foot of lumber will weigh about 4-1/2 pounds, which is heavier than North American lumber.
Drying. Drying is slow. Warping is minimal. Most wenge is dried before it arrives in North America.
Shrinkage in drying from green to 6 percent MC is estimated to be 4-1/2 percent tangentially (the width of flatsawn lumber) and 2-1/2% radially (quartersawn width). This is quite small.
Gluing and machining. Wenge will often be quite resinous, which leads to problems when gluing. Surfaces should be freshly prepared and should then be cleaned with a solvent moments before gluing, similar to gluing teak.
The wood is so dense that it is hard to machine and the heat generated rapidly dulls tools. Tools must be kept as sharp as possible for best performance.
Splinters of wenge cause persistent inflammation. Exposure to the sawdust can cause abdominal cramps, eye irritation and breathing problems.
Stability. This wood is very stable, requiring a change of 6 percent MC for a 1 percent size change tangentially and a 12 percent MC change radially. This is less than half the movement of red oak. Because it moves so little, one might be tempted to use wood that is a bit higher in MC than normal for other hardwoods. I suggest using wood no higher than 9 percent MC; check the MC before using.
Strength. Wenge is very strong (MOR is 16,200 psi) and very stiff (MOE is 1.97 million psi). It is also quite hard, with a rating of 1630 pounds. The wood is also high in shock resistance; hence its use for sporting goods and tool handles.
Color and grain. The heartwood is dark brown with fine, closely-spaced black lines that are very striking on a quartersawn surface. A flatsawn surface also has a striking pattern. The grain is coarse with large open vessels, similar to red oak. The grain is usually fairly straight.
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