Wood species
Aspen wood
Aspen is a hardwood; this page covers the aspen, led by quaking aspen (Populus tremuloides). At 12% moisture content it has a Janka hardness of 350 lbf (1,557 N) and it weighs about 27 lb/ft³ (426 kg/m³), 2.2 lb (1 kg) per board foot.
Names and species on this page: quaking aspen, bigtooth aspen.
Key numbers
- Janka hardness, 12% MC
- 350 lbf (1,557 N)
- Green: 300 lbf (1,334 N)
- Weight at 12% MC
- 27 lb/ft³ (426 kg/m³)
- 2.2 lb per board foot
- Specific gravity (oven-dry weight)
- 0.38 at 12% MC volume
- 0.35 on green volume
- Shrinkage, green to oven-dry
- 6.7% tangential
- Radial 3.5%, volumetric 11.5%
One source: USDA Forest Products Laboratory, the authority for species properties it measured
Why: Measured by the USDA Forest Products Laboratory; aspen's density is worked from its specific gravity with the Handbook's own equation.
How much aspen moves
A 12 in wide flatsawn board of quaking aspen that goes from 6% to 12% moisture content swells about 0.17 in (about 5/32 in, 4.3 mm). Quartersawn, the same board moves about 0.09 in (about 3/32 in, 2.2 mm). Flatsawn faces move 1.9 times as much as quartersawn ones, because the wood shrinks 6.7% around the growth rings but only 3.5% across them.
Worked with the Wood Handbook's dimensional change coefficients for quaking aspen (Table 13-5: 0.00234 tangential, 0.00119 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
- Grayish white to light grayish brown heartwood that fades gradually into lighter sapwood.
- Grain and texture
- Usually straight, with a fine, even texture.
- Working and character
- Light and soft, low in strength and fairly high in shrinkage, but easy to work. Dry aspen gives no odor or taste to food.
- Uses
- Lumber, pallets, boxes and crates, turned items, matches and veneer; a preferred species for oriented strandboard.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-4.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Clear, straight-grained samples of quaking aspen 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) | 5,100 psi (35 MPa) | 8,400 psi (58 MPa) |
| Stiffness (MOE) | 860,000 psi (5.9 GPa) | 1,180,000 psi (8.1 GPa) |
| Crushing strength (compression parallel to grain) | 2,140 psi (15 MPa) | 4,250 psi (29 MPa) |
| Compression perpendicular to grain | 180 psi (1 MPa) | 370 psi (3 MPa) |
| Shear parallel to grain | 660 psi (5 MPa) | 850 psi (6 MPa) |
| Tension perpendicular to grain | 230 psi (2 MPa) | 260 psi (2 MPa) |
A dash means the Handbook prints no value; none is filled in.
The aspen
The Handbook tests each species separately; they are sold together as aspen. Across the 1 species measured, Janka hardness at 12% runs from 350 to 350 lbf.
| Species | Janka, 12% MC | Weight, 12% MC | Tangential shrinkage |
|---|---|---|---|
| Quaking aspenPopulus tremuloides | 350 lbf | 27 lb/ft³ | 6.7% |
| Bigtooth aspenPopulus grandidentata | — | 27 lb/ft³ | 7.9% |
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 quaking aspen at 350 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 × 0.38 × 1.12.
Arithmetic: exact by definition , sources [1]
The number
About 27 lb/ft³, or 2.2 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources