In North America, the maple species are divided into two groups: soft maple (which includes red maple, Acer rubrum, silver maple, A. saccharinum, and bigleaf maple, A. macrophyllum) and hard maple (which includes sugar maple, A. Saccharum, and black maple, A. Nigrum). Once the lumber is manufactured, it is possible with 10x magnification to separate hard maple from soft maple as hard maples have rays cells of two different widths (seen from the end grain) while soft maples have one width. Soft maple also tends to be softer, lighter weight, weaker and more dingy colored than hard maple.
There are a variety of local names for maple. Two examples: silver leaf maple is silver maple; Oregon maple is bigleaf maple.
Of the two main soft maples, red maple is about 10 percent harder and 15 percent heavier than silver maple. Red is also stronger and stiffer than silver. It is not unusual to have lumber buyers indicate that they want red maple rather than just soft maple.
Red maple grows throughout the East Coast, from Florida to Newfoundland and west to Texas and Minnesota. It prefers wetter sites, but grows in a wide variety of climatic and soil conditions. Trees are typically 70 feet high and 24 inches in diameter at maturity, but larger trees do exist. It has bright red leaves in the fall. It is the state tree of Rhode Island.
Silver maple also grows along the East Coast, but is not found commercially in Florida, Louisiana or Texas. Silver maple trees are a bit taller and a bit larger in diameter than red maple. Silver maples also have the largest winged seeds of all the maples. Silver maples leaves turn yellow in the fall.
Red and silver maple are a highly desirable wildlife browse food. Elk and white-tailed deer especially use the current season's growth of red maple for winter food. Squirrels like early spring seeds. Beavers eat small diameter material. Birds eat the seeds. By adding sulfate of iron to the tannin extracted from the bark, pioneers were able to make ink.
Although not as strong as hard maple, the name "soft" gives the wrong impression. Soft maple is more than adequate for many uses, including furniture, flooring, cabinets, kitchenware, clothes hangers and the like. Red and silver maple also can be used for syrup production, although the good sugar season is earlier and shorter and yields are less than with hard maple.
Processing characteristics and suggestions
Red maple weighs about 36 pounds per cubic foot at 7 percent MC. This means that a piece of lumber planed to 3/4 inch will weigh 2-1/4 pounds. Silver maple weighs about 31 pounds per cubic foot at 7 percent MC. Dry, planed lumber will weigh just under 2 pounds per BF.
Drying is easy. There is little risk of checking and warp with proper stacking and proper drying conditions.
Slow drying can develop stain, both fungal and chemical, so aggressive drying ASAP after sawing is suggested, especially for clearer more valuable lumber. Dry stickers are essential as well. In air drying, protecting the lumber from rain wetting is important.
Shrinkage in drying averages about 6 percent in width for flatsawn lumber and 3 percent in thickness.
Gluing and machining
Red and silver maple are excellent gluing woods even if conditions or gluing variables are not perfect. These maples are very easy to machine. Due to the softness of the wood, very sharp tools work best. Avoid moisture contents over 8.0 percent MC for best machining.
The soft maples are less responsive to humidity changes than the hard maples. For flatsawn lumber, a 4 percent MC change results in 1 percent shrinkage or swelling. In the radial direction or thickness of flatsawn lumber, an 8 percent MC change results in 1 percent size change.
Red maple has an ultimate strength in bending (MOR) of 7700 psi, a stiffness (MOE) of 1.39 million psi and surface hardness of 700 pounds. Silver maple has an MOR of 5800 psi, MOE of 0.94 million psi and hardness of 590 pounds. Hard maple comparable values are 9400 psi, 1.55 million psi and 970 pounds.
Color and grain
The grain of these two maples is very fine textured with white sapwood (if dried rapidly). Heartwood is buff colored to darker brown with sometimes a greenish coloration.
One unique characteristics of soft maples is the development of small boat shaped (or oval shaped) discolorations (several inches long and 1/4 to 1-1/5 inch wide). Oftentimes there will be two or three 1/8-inch diameter holes in the discoloration, adjacent to each other. These characteristics are a result of the Columbian timber beetle activity in the living tree. This striking defect adds a great deal of character to an otherwise plain wood appearance.
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