Wood species
Sweetgum wood
Sweetgum is a hardwood (Liquidambar styraciflua). At 12% moisture content it has a Janka hardness of 850 lbf (3,781 N) and it weighs about 36 lb/ft³ (582 kg/m³), 3 lb (1.37 kg) per board foot.
Also called: redgum, sap gum.
Key numbers
- Janka hardness, 12% MC
- 850 lbf (3,781 N)
- Green: 600 lbf (2,669 N)
- Weight at 12% MC
- 36 lb/ft³ (582 kg/m³)
- 3 lb per board foot
- Specific gravity (oven-dry weight)
- 0.52 at 12% MC volume
- 0.46 on green volume
- Shrinkage, green to oven-dry
- 10.2% tangential
- Radial 5.3%, volumetric 15.8%
One source: USDA Forest Products Laboratory, the authority for species properties it measured
Why: Measured by the USDA Forest Products Laboratory; sweetgum's density is worked from its specific gravity with the Handbook's own equation.
How much sweetgum moves
A 12 in wide flatsawn board of sweetgum that goes from 6% to 12% moisture content swells about 0.26 in (about 1/4 in, 6.7 mm). Quartersawn, the same board moves about 0.13 in (about 1/8 in, 3.3 mm). Flatsawn faces move 1.9 times as much as quartersawn ones, because the wood shrinks 10.2% around the growth rings but only 5.3% across them.
Worked with the Wood Handbook's dimensional change coefficients for sweetgum (Table 13-5: 0.00365 tangential, 0.00183 radial per 1% change in moisture content), which hold between 6% and 14%. Individual boards vary: the Handbook gives shrinkage a coefficient of variation of about 15% (p. 4-11).
Color, grain and working
- Color
- Sold as sap gum (the light sapwood) or redgum (the reddish-brown heartwood).
- Grain and texture
- Often interlocked, which gives a ribbon stripe when quartersawn.
- Working and character
- Moderately heavy, hard, strong and stiff. The interlocked grain means it must be dried slowly.
- Uses
- Furniture, interior molding, millwork, veneer, plywood, boxes and crates.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-9 to 2-10.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Clear, straight-grained samples of sweetgum tested by the Forest Products Laboratory (Wood Handbook Table 5-3b). Knots and cross grain make lumber weaker than these clear samples (Handbook Chapter 5).
| Property | Green | 12% MC |
|---|---|---|
| Bending strength (MOR) | 7,100 psi (49 MPa) | 12,500 psi (86 MPa) |
| Stiffness (MOE) | 1,200,000 psi (8.3 GPa) | 1,640,000 psi (11.3 GPa) |
| Crushing strength (compression parallel to grain) | 3,040 psi (21 MPa) | 6,320 psi (44 MPa) |
| Compression perpendicular to grain | 370 psi (3 MPa) | 620 psi (4 MPa) |
| Shear parallel to grain | 990 psi (7 MPa) | 1,600 psi (11 MPa) |
| Tension perpendicular to grain | 540 psi (4 MPa) | 760 psi (5 MPa) |
A dash means the Handbook prints no value; none is filled in.
Dust and health
- Wood dust is classed as carcinogenic to humans (Group 1) by the International Agency for Research on Cancer, chiefly for cancers of the nose and sinuses.
- NIOSH recommends keeping wood dust exposure to 1 mg/m³ of total dust, as quoted in OSHA's sawmill guidance.
This is what the named authorities publish, not medical advice.
Compare with
Why these numbers
Why these numbers?
The situation
The USDA Forest Products Laboratory measured sweetgum at 850 lbf of side hardness at 12% moisture content, on clear, straight-grained samples (Wood Handbook Table 5-3b).
One source: USDA Forest Products Laboratory, the authority for species properties it measured , sources [1]
What that means
Side hardness (Janka) is the load needed to press a 0.444 in (11.28 mm) steel ball halfway into the wood across the grain; a higher number dents less (Handbook p. 5-5).
One source: USDA Forest Products Laboratory, the authority for species properties it measured , sources [1]
So
Density at 12% is water's density × specific gravity × (1 + 0.12) (Handbook Eq. 4-14): 62.43 × 0.52 × 1.12.
Arithmetic: exact by definition , sources [1]
The number
About 36 lb/ft³, or 3 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources