Wood species
Black ash wood
Black ash is a hardwood (Fraxinus nigra). At 12% moisture content it has a Janka hardness of 850 lbf (3,781 N) and it weighs about 34 lb/ft³ (549 kg/m³), 2.9 lb (1.3 kg) per board foot.
Also called: Fraxinus nigra.
Key numbers
- Janka hardness, 12% MC
- 850 lbf (3,781 N)
- Green: 520 lbf (2,313 N)
- Weight at 12% MC
- 34 lb/ft³ (549 kg/m³)
- 2.9 lb per board foot
- Specific gravity (oven-dry weight)
- 0.49 at 12% MC volume
- 0.45 on green volume
- Shrinkage, green to oven-dry
- 7.8% tangential
- Radial 5.0%, volumetric 15.2%
One source: USDA Forest Products Laboratory, the authority for species properties it measured
Why: Measured by the USDA Forest Products Laboratory; black ash's density is worked from its specific gravity with the Handbook's own equation.
How much black ash moves
A 12 in wide flatsawn board of black ash that goes from 6% to 12% moisture content swells about 0.2 in (about 3/16 in, 5 mm). Quartersawn, the same board moves about 0.12 in (about 1/8 in, 3.1 mm). Flatsawn faces move 1.6 times as much as quartersawn ones, because the wood shrinks 7.8% around the growth rings but only 5.0% across them.
Worked with the Wood Handbook's dimensional change coefficients for black ash (Table 13-5: 0.00274 tangential, 0.00172 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
- Darker brown heartwood than American white ash, with light to nearly white sapwood.
- Working and character
- Lighter than the white ash group: the Handbook gives the black ash group a basic specific gravity of 0.45 to 0.48, against more than 0.50 for white ash.
- Uses
- Decorative veneer, cabinets, millwork, furniture, cooperage and crates.
The Handbook reports that the IUCN lists black ash as critically endangered because of the emerald ash borer, and that live and dead trees are being widely harvested.
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 black ash 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) | 6,000 psi (41 MPa) | 12,600 psi (87 MPa) |
| Stiffness (MOE) | 1,040,000 psi (7.2 GPa) | 1,600,000 psi (11 GPa) |
| Crushing strength (compression parallel to grain) | 2,300 psi (16 MPa) | 5,970 psi (41 MPa) |
| Compression perpendicular to grain | 350 psi (2 MPa) | 760 psi (5 MPa) |
| Shear parallel to grain | 860 psi (6 MPa) | 1,570 psi (11 MPa) |
| Tension perpendicular to grain | 490 psi (3 MPa) | 700 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
Buying and finishing black ash
Work it out for your project
- Rank woods for furniture with the species picker
Weigh black ash against other woods on hardness, weight, movement and color, every figure from the Wood Handbook.
- Plan a finish for furniture in black ash
The finishes whose makers name that use, and a dated coat schedule from each product’s own sheet.
Why these numbers
Why these numbers?
The situation
The USDA Forest Products Laboratory measured black ash 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 × 0.49 × 1.12.
Arithmetic: exact by definition , sources [1]
The number
About 34 lb/ft³, or 2.9 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources