Properties and Uses of Balsa

Balsa (Ochronia lagopus SW.) is the lightest wood in commerce. A fast-growing hardwood in Central and South America (principally Ecuador) it produces two 16-foot logs of 15 inches diameter in 6 or 7 years. The soft-textured wood requires care to prevent staining during manufacture, allowing but 3 days from saw to kiln. Chemical preservative sprays are commonly used. Three density levels are recognized; light, medium, and firm. Tabulated values of mechanical properties for the three classes show specific gravities of 0.10, 0.18, 0.25 respectively. Comparable moduli of rupture in bending are–1,375 psi, 1,725 psi, 2,535 psi; moduli of elasticity–280,000 psi, 625,000 psi, 925,000 psi. Other properties are tabulated, including the effect of high temperature on coloration and checking, and comparisons with similar materials. The physical properties important to the wide range of uses are 1) lightness, 2) structural strength, 3) insulating properties, 4) bouyancy, 5) dimensional stability, 6) durability, and 7) workability. Principal uses are discussed including core stock for doors, boat hulls, aircraft panels, insulation for walls or partitions, buoyant articles in marine applications, and material for hobby crafts.

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