Woods to Know: African Blackwood | Canadian Woodworking

Woods to Know: African Blackwood

African Blackwood (Dalbergia melanoxylon)

Aptly called the 'tree of music', African Blackwood is a well known tone wood for woodwinds and stringed instruments. It is a dense waxy wood, excellent in holding fine detail, which makes it one of the finest choices for woodturning.
 
A member of the Rosewood family, African Blackwood is a widespread species in sub-Saharan Africa, growing south to the Transvaal in South Africa. It prefers a solitary existence and favours a dry climate. Tanzania and Mozambique are the primary exporting countries.

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It is a small, slow growing tree typically 12' to 45' tall, with diameters around one foot. In the past, exceptional individuals 60' tall and 3' in diameter were harvested. It can take up to 60 years to mature and the older trees can have buttressed trunks. These trees often have heart rot and other structural defects.
 
The name Blackwood derives from the inky black heartwood in the mature tree. The heart in younger trees ranges from a deep dark brown to an indigo shade of black.  Slower growing trees with limited water uptake are reported to produce the deepest black colouration. The sharply demarcated sapwood is a creamy yellow-white and is less dense than the heart.  
 
The wood is extremely dense with a fine even texture. It can be difficult to dry and the sapwood is usually left on to help season the material without cracking the heart. It must be dried slowly (no kiln drying) and is often coated in wax to help slow down the process. Once dry, it is very stable in all directions. 
 
Given its limited stature, African Blackwood is usually found as small logs, cants, and smaller dimensional blocks. Tooling has to be extremely sharp to deal with this dense wood. Screw holes have to be predrilled. It turns exceptionally well, producing detailed pieces with a lustrous surface that does not need to be finished. When carved, it holds detail extremely well.

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African Blackwood end-grain
 
The indigenous carving co-ops of Central Africa use it for all manner of carved figures. Chessman, walking sticks, pulleys, and duck calls have also used this fine turning wood. The high density, stability, and waxiness of the wood make African Blackwood ideal for woodwind instruments. When these instruments are played, hot moist air is blown into them. This creates a moisture and temperature gradient in the wood. The resulting stresses can crack the instrument and cause tuning issues. The African Blackwood's inherent characteristics minimize these problems. Clarinets, oboes, flutes, and bagpipes all use African Blackwood. It is also found in guitar backs and sides as well as banjo tone rings and fingerboards. Since it holds screws very well, musical hardware attaches to all these instruments with little problem.  
 
The demand for Blackwood is high and, of course, that means stocks are declining and the tree is now vulnerable. Little is known about its botanical characteristics, so it is hard to properly assess its future. At the very least, it is undergoing a process of commercial extinction. The large desirable trees are being cut down which weakens the genetic diversity of the species. The larger trees can't reproduce, potentially shifting the population to the less desirable individuals. There are groups dedicated to preserving this species, and FSC approved Blackwood is now available to supply the musical instrument trade.
 
Despite these concerns, working with African Blackwood is a highlight for any woodworker. It can be very expensive (due to the high waste factor in processing), but small blocks and shorts are available at a reasonable price for small turnings, accents, inlays, and other uses. With conscientious use, woodworkers can help this exceptional species survive and prosper. 

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Spanish Olive Hollow Vessels with African Blackwood Accents (Paul Ross)
 
 
Average Dried Weight79 lbs/ft³A measure of its weight at 12% moisture and an ambient temperature of 70°F.
Specific Gravity1.27A measure of the ratio of its density compared to water (at 12% MC)
ShrinkageRadial: 2.9%,
Tangential: 4.8%,
Volumetric: 7.7%
Radial (the amount of crosswise shrinkage);
Tangential (the amount of lengthwise shrinkage);
Volumetric (the total amount of shrinkage.)
T/R Ratio1.7A measure of the uniformity of tangential to radial shrinkage.
Janka Hardness3,670 lbfA measure of resistance to denting and abrasion.
Crushing Strength10,570 lbf/in²A measure of compression strength parallel to the grain.
Colour
Heartwood is a deep black, sometimes a dark brown or purple. Sapwood is clearly demarcated with a creamy yellow white.
GrainStraight grained.
TextureFine even texture.
Workability
Difficult to work, requires sharp tooling. Excellent turning wood with an outstanding ability to hold fine details.
UsesWoodwind and string instruments, carved objects, all sorts of turned pieces.
Price$48.00/bf 4/4
Usually sold in blanks. Typical prices:
2" x 2" x 24": $82.00
1-1/2" x 1-1/2" x 16": $32.00
1-1/8" x 1-1/8" x 16": $14.00
 
  
Photos and Specifications Courtesy of: The Wood Database