Roasting Wood for Strength
Name: Robert B.
Date: Febraury 2003
I was once told that the native Americans would "roast"
their spears over a fire to make the wood stronger. Is it true that
heating wood or burning it to a certain point makes the wood stronger?
I do not know much about what the native Americans did with wood, but it
seems very plausible. The following advantages of dried wood are given in
the USDA Forest Service publication titled Drying Hardwood Lumber:
"Some advantages of dried lumber over undried or partially dried lumber are
- Lumber with less than 20% maximum moisture content (MC) has no risk of
developing stain, decay, or mold as a result of fungal activity.
- Dry lumber is typically more than twice as strong and nearly twice as
stiff as wet lumber.
- Fasteners driven into dry lumber, including nails and screws, will perform
much better than do fasteners in wet lumber, especially if the wet lumber
dries after fastening.
- Dry lumber weighs 40% to 50% less than wet, undried lumber. For example,
an 18-wheel, flatbed truck can haul about 7,500 board feet of wet lumber,
10,500 board feet of partially dried lumber, and 12,500 board feet of
- Products made from properly dried lumber will shrink very little or none
at all while in service; products made from wet lumber often shrink
substantially as the wood dries.
- Gluing, machining, and finishing are much easier to accomplish with dry
- Wood that will be treated with fire retardants or preservatives (such as
copper chromium arsenate, CCA) after drying must be at least partially dried
to allow for quick penetration of the treating chemicals."
So, it is pretty obvious that drying of wood imparts some very positive
properties, included increased strength, reduced weight, and less tendency
to warp or shrink as it ages. If you would like to learn more about the
mechanisms that improve the wood through drying, you can visit the web site
of the Forest Service's Forest Product Laboratory at the University of
Wisconsin. Their address is www.fpl.fs.fed.us. Go to their publications
link to download the publication on hardwood drying and many other
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Update: June 2012