African padauk
August 15, 2010 | 7:00 pm CDT

There are three species of trees that produce lumber that we call padauk: Burma padauk, Andaman padauk (named for the Andaman Islands in the South Atlantic where it grows) and African padauk. All are legume family, grow in tropical rain forests, and have the Latin names of Pterocarpus macrocarpus, P. dalbergioides, and P. soyauxii.

African padauk, the more commonly seen species of lumber in North America, grows in central Africa, including Gabon, Congo, Cameroon, Nigeria and Ivory Coast. The larger trees at maturity are often up to 100 feet tall and 4 feet in diameter.

The bark yields a wonderful, bright red dye that was used for body coloring for religious festivals by native Africans. The wood itself is also quite red. When working with padauk, the fine red dust can coat everything in sight if the dust removal system is not adequate. Any dust on clothes will color the wash water for a load or two.

Padauk is an excellent turning wood and is widely used for fancy turnery such as knife and tool handles. It is also prized for high-end cabinets, furniture, carving, veneer, inlay, flooring, dyewood, joinery, dowels, shuttles, spindles, paddles and boat building. Due to the high cost of this wood, it is used today mainly for accent purposes. Overall, however, it is a wonderful wood; I wish there was more available.

Processing suggestions and characteristics

Density. Padauk is a fairly dense wood, with a kiln-dried density that ranges between 41 to 50 pounds per cubic foot. A board foot of lumber will weigh about 4 pounds, which is similar to hickory.

Drying. Even though this is a high-density wood, it dries very well with a minimum of loss in the kiln. In most cases, it would be air-dried or kiln-dried before shipping to North America.

Shrinkage green to 6 percent MC is 4.2 percent tangentially (the width of a flatsawn piece of lumber) and 2.6 percent radially (the width of quartersawn).

Gluing and machining. As with all dense woods, the surfaces to be glued must be straight and true. As there can be a bit of oil in this wood from time to time, surfaces to be glued should be less than 30 minutes old. It would be prudent to wash older surfaces with a solvent before gluing.

This wood does machine well both with hand and machine tools. Because of interlocked grain (which is when the grain in the piece is not parallel to the faces lengthwise but sometimes dives into the piece and sometimes comes out of the piece, alternating from year to year), it is hard to finish the wood surfaces smoothly unless tools are sharp and sandpaper is fresh.

Of special note is that the sawdust, in addition to being red, is a nasal irritant and can cause respiratory problems. Splinters from rough lumber can also cause irritation.

Stability. The wood is exceptionally stable when the moisture content changes. It takes more than a 7 percent MC change to cause a 1 percent size change tangentially and 10 percent MC change radially.

Strength. As might be expected for a dense wood, it is very strong (MOR is 18,600 psi) and stiff (MOE is 1.75 million psi). The wood is also very hard. Screw and nail holding are very good, but predrilling of holes for fasteners is wise.

Color and grain. The grain is at times very straight and at other times it is interlocked. Overall, the texture would be rated as coarse with large pores, similar to red oak. The heartwood is rich red to purple red heartwood; the color darkens appreciably with exposure to light. The sapwood, 4 to 8 inches wide in a log, is white. With the natural oil in the wood, it finishes to a beautiful sheen.

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About the author
Gene Wengert

Gene Wengert, “The Wood Doctor” has been training people in efficient use of wood for 35 years. He is extension specialist emeritus at the University of Wisconsin-Madison.