The true firs, called true firs to distinguish the wood from Douglas-fir, consist of more than 40 species in North America, but only seven species produce commercial lumber. In eastern North America, there is one main species, balsam fir (Abies balsamea) ranging from Alberta to Newfoundland, south to Wisconsin and New York. The majority of the timber is in Canada; balsam fir is the official tree of New Brunswick.
In the western side of the continent, the commercial fir lumber species are subalpine fir (A. Lasiocarpa), California red fir (A. Magnifica), grand fir (A. Grandis), noble fir (A. Procera), Pacific silver fir (A. Amabilis) and white fir (A. Concolor). Although the trees can easily be separated into separate species, once cut into lumber, the wood of all the firs looks alike.
Balsam fir is the most symmetrical of northeastern coniferous species, with a narrow pyramidal crown that terminates in a slender spire-like tip. The typical balsam fir tree is about 60 feet tall and 1-1/2 feet in diameter, although much larger trees (90 feet tall and 2-1/2 feet diameter) are seen.
Balsam firs are popular for Christmas trees as the needles stay fresh for a long time.
The wood is used for furniture, construction lumber (2×4, 2×6), particleboard, and pulp. As construction lumber, the grade stamp will indicate the species as SPF (spruce, pine and fir); the fir is balsam fir, also called Canadian fir or eastern fir.
There are some reports of contact dermatitis from the resin from the true firs.
Processing suggestions and characteristics
Density. The true firs are one of the lightest weight softwoods in North America, averaging about 25 pounds per cubic foot at 10 percent MC. This is equivalent to 1.4 pounds per board foot for 8 percent MC, ¾-inch planed lumber.
Drying. The firs have a high risk of developing fungal blue stain (also called sap stain) and becoming infested with ambrosia beetles that leave small holes in the sapwood when the MC is high. Rapid handling from log to the kiln, or other dying systems, is required to avoid and control these risks. This wood dries very easily. Drying defects are few. Shrinkage in drying is under 5 percent. The final MC for spruce should be between 8.0 to 9.5 percent MC.
Gluing and machining. Gluing is excellent. The wood is very forgiving even if gluing parameters are not perfect. Machining is excellent so long as tools are very sharp.
Stability. The wood is quite stable when the MC changes. It takes over 4 percent MC change to develop 1 percent shrinkage in the width of flatsawn lumber (tangentially) and 10 percent MC change to the thickness by 1 percent (radially).
Strength. For balsam fir, the ultimate strength (MOR) is 9,200 psi; the stiffness (MOE) is 1.45 million psi; the hardness is 400 pounds.
Color and grain. Firs are a straight grain, odorless, white or pale white uniformly colored wood. The sapwood and heartwood have the same color and cannot be easily separated. Small, tight, red knots are common and add character to the wood. A premium “knotty pine” look is easily obtained.
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