USDA Forest Service
Forest Products Laboratory
One Gifford Pinchot Drive
Madison, WI 53705-2398
(608) 231-9200

 

Wood Technical Fact Sheet

 

 Pterygota spp.

Pterygota

Family: Sterculiaceae

Other Common Names: Kyere, Awari, Okyere (Ghana), Koto (Ivory Coast), Poroposo, Kefe (Nigeria).

Distribution: Common in tropical evergreen and mixed deciduous forests of West Africa.

The Tree: May reach a height of 120 ft; bole rather straight and cylindrical, clear to 40 to 80 ft, buttressed to 20 ft; trunk diameters 2 to 4 ft.

The Wood:

General Characteristics: Wood pale yellow to a creamy white with little differentiation between sapwood and heartwood. Texture rather coarse; grain straight to interlocked; green material has an unpleasant smell which disappears on drying; high rays give a conspicuous flecked figure; commonly with small knot

clusters.

Weight: Basic specific gravity (ovendry weight/green volume) 0.47 to 0.56; air-dry density 35 to 43 pcf.

Mechanical Properties: (2-cm standard)

Moisture content Bending strength Modulus of elasticity Maximum crushing strength

(%) (Psi) (1,000 psi) (Psi)

Green (9) 10,600 1,270 5,130

12% 16,100 1,670 8,400

Green (9) 8,300 1,080 3,870

12% 12,300 1,340 6,300

12% (47) 17,800 2,140 8,450

Janka side hardness 670 to 790 lb for green material and 940 to 970 lb for dry. Amsler toughness 260 in.-lb at 12% moisture content (2-cm specimen).

Drying and Shrinkage: Timber seasons fairly rapidly with only a slight tendency to check or warp. Kiln schedule T10-D4S is suggested for 4/4 stock and T8-D3S for 8/4. Shrinkage green to ovendry: radial 5.7%; tangential 11.4%; volumetric 15.0%. Movement in service rated as medium.

Working Properties: Works fairly easily with hand and machine tools, a cutting angle of 20 degrees is suggested to reduce tearing of interlocked grain in planing, glues and nails satisfactorily, peels and slices into veneers satisfactorily.

Durability: Heartwood is not durable and is liable to termite attack; sapwood liable to powder-post beetle attack. Logs are prone to stain and insect attack requiring rapid removal from the forest or a chemical treatment.

Preservation: Heartwood moderately resistant to impregnation; sapwood permeable.

Uses: Furniture components, joinery, general carpentry, boxes and crates, plywood.

Additional Reading: (3), (9), (47)