Tropical wood · Southeast Asia and Oceania
Geronggang wood
Geronggang (Cratoxylon arborescens, family Guttiferae) is a tropical timber from Southeast Asia and Oceania. Green, its Janka hardness is 420 lbf (1,868 N), and air-dry it weighs about 30 lb/ft³ (481 kg/m³). The figures are from the USDA Forest Products Laboratory's Tropical Timbers of the World, pp. 599–600.
Other names, by country: Serungan (Sabah, Northern Sarawak, Brunei).
Key numbers
- Janka hardness, dry
- Not printed
- Green: 420 lbf (1,868 N)
- As printed: “Janka side hardness 420 lb for green material.”
- Air-dry density
- 30 lb/ft³ (481 kg/m³)
- Basic specific gravity
- 0.40 oven-dry weight, green volume
- As printed: “Basic specific gravity (ovendry weight/green volume) 0.40; air-dry density 30 pcf.”
- Shrinkage, green to air-dry
- 4.7% tangential
- Radial 2.6%
One source: USDA Forest Products Laboratory, Tropical Timbers of the World (Chudnoff, 1979 edition), the only published source read for this wood
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE); crushing strength is compression parallel to the grain. The sheet collects these from published tests: it prints one data set, each at the moisture content printed beside it, never restated as 12%.
| Moisture | Bending strength (MOR) | Stiffness (MOE) | Crushing strength |
|---|---|---|---|
| Green | 5,750 psi (40 MPa) | 1.16 million psi (8 GPa) | 2,660 psi (18 MPa) |
A dash means the sheet prints no value; none is filled in.
What the data sheet says
- Color, grain and texture
- Heartwood varies from light brick-red to dark pink, darkening upon exposure; sapwood yellow, sometimes with a pink or orange tinge, usually clearly demarcated. Texture uniform and rather coarse; grain typically straight, sometimes interlocked; lustrous; without distinctive odor or taste.
- Working properties
- The timber saws without difficulty and dresses to a smooth surface but cutters are reported to dull rapidly.
- Durability
- Rapidly attacked by decay fungi if in ground contact and vulnerable to termites. Not resistant to marine borers.
- Uses
- Furniture, joinery, veneer and plywood, light construction, particleboard, fiberboard. Reported to make good roofing shingles if impregnated with preservatives.
- Where it grows
- Locally common in Malaysia and Indonesia, mainly in coastal dipterocarp swamp forests.
Quoted from Tropical Timbers of the World, pp. 599–600, a USDA Forest Products Laboratory work in the public domain.
Work it out for your project
- Rank woods for furniture with the species picker
Weigh geronggang against other woods on hardness, weight, movement and color, every figure from the Wood Handbook.