Soft, lightweight and flexible, balsa wood is easy to work and inexpensive to use for hobbies and home construction. Grown in tropical rain forests, its name means "raft" in Spanish, since it floats well. Balsa has excellent properties for such applications as energy and sound insulation, lamination, and making surfboards and musical instruments.
Like all woods, balsa has a density rating measured in pounds per cubic foot. Balsa's lightest-rated woods are ultra-light, 4 to 5.4 lbs.; light at 5.5 to 6.5 lbs.; and medium-light at 6.6 to 7.5 lbs. These woods are mostly used by professional airplane-model builders. The common type for hobbies is medium to medium-hard wood, 7.6 to 12 lbs. per cubic foot. Balsa's densest wood rates 13 lbs. or more and is used in home construction.
Balsa wood comes in three different grains, from supple to stiff. The most flexible is A-grain, with long fibers or grain lines. It bends well, especially when wet, but warps easily. B, or mixed-grain, is an all-purpose wood with moderate flexibility and shorter grain lines. One side or edge may remain rigid, while the other bends a little. The stiffest balsa wood is C-grain, giving it additional strength. Its fibers are extremely short, making the grain more resilient to warping.
Due to balsa's large pores, it quickly soaks up the first layer of stain or paint. However, once the pores close, its grain accepts all finishes with ease. Balsa's straight grain cuts with basic hobby tools, such as X-acto knives with various blades or fine-grit sandpaper. Wood glue is the best method to join balsa pieces together.
Balsa's light-colored outer sapwood is usually pale white or yellow to tan, with a light grain. The heartwood near the center of the tree is pink to reddish-brown. The darker grain is more prominent and deepens when stained. Balsa's natural look can be protected with a clear sealer.
A variety of sizes for balsa wood adds to its versatility in hobby crafts. It is available in sheets, sticks and blocks. Sheet widths include 2 inches to 6 inches with 24- to 48-inch lengths. Balsa sticks measure 36 to 48 inches long. The standard thickness for sheets and sticks ranges from 1/32 inch to 1/2 inch. Excellent for carving, blocks are 1 to 3 feet long, 2 to 4 inches thick and up to 6 inches wide.
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