Thermally Modified Ash (White Ash)
Fraxinus americana · Hardwood
- Type
- Hardwood
- Origin
- Native to Eastern North America (Northern US and Canada).
- Hardness
- 1,320 lbf (Hard) - Note: Thermal modification slightly reduces impact toughness while maintaining surface hardness.
- Durability
- Very Durable. The thermal process removes hemi-celluloses (sugars), making it highly resistant to rot, fungi, and insect attack compared to untreated ash.
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Grain Pattern
Strong cathedral grain figure with prominent growth rings; coarse texture and straight grain characteristic of ring-porous hardwoods.
Color & Appearance
Even chocolate brown throughout. Thermal modification (torrefaction) has darkened the naturally light heartwood/sapwood into a uniform, rich dark tone that persists through the board.
Hardness (Janka)
1,320 lbf (Hard) - Note: Thermal modification slightly reduces impact toughness while maintaining surface hardness.
Durability & Decay Resistance
Very Durable. The thermal process removes hemi-celluloses (sugars), making it highly resistant to rot, fungi, and insect attack compared to untreated ash.
Value & Sustainability
- Estimated Market Value
- $8.00 - $12.00 per board foot (Thermally modified stock carries a premium over standard ash).
- Wood Age Estimate
- Relatively modern stock (under 5 years); show signs of recent machining but the dark color is a result of industrial heat-treatment, not natural oxidation.
- Sustainability Status
- Generally available as FSC certified; however, North American Ash is currently under severe threat from the Emerald Ash Borer beetle (Critically Endangered per IUCN).
Common Uses
Exterior decking, cladding, outdoor furniture, siding, flooring, and high-end cabinetry where rot resistance is required.
Geographic Origin
Native to Eastern North America (Northern US and Canada).
Workability
Excellent. Planes and sands very cleanly, though it is more brittle than untreated wood. Pre-drilling is essential as heat-treated wood is prone to splitting.
Finish Recommendations
Penetrating UV-inhibiting oils to maintain the chocolate color, or can be left unfinished to weather to a silver-grey; avoid high-build films.
Notable Features
Distinctive burnt or toasted sweet scent; extremely stable with very low moisture content (approx 4-6%); lacks the elasticity of natural ash.
