Balsa (Ochroma pyramidale) is widely distributed throughout tropical America from southern Mexico to southern Brazil and Bolivia, but Ecuador has been the principal source of supply since the wood gained commercial importance. It is usually found at lower elevations, especially on bottomland soils along streams and in clearings and cutover forests. Today, it is often cultivated in plantations.
Several characteristics make balsa suitable for a wide variety of uses. It is the lightest and softest of all woods on the market. The lumber selected for use in the United States weighs, on the average, about 180 kg/m3 (11 lb/ft3) when dry and often as little as 100 kg/m3 (6 lb/ft3). The wood is readily recognized by its light weight; nearly white or oatmeal color, often with a yellowish or pinkish hue; and unique velvety feel.
Because of its light weight and exceedingly porous composition, balsa is highly efficient in uses where buoyancy, insulation against heat or cold, or low propagation of sound and vibration are important. Principal uses are for life-saving equipment, floats, rafts, corestock, insulation, cushioning, sound modifiers, models, and novelties.
*Much of the base wood information presented here is made available by the USDA FPL FS. If you are interested in a much more technical description of wood properties, I encourage you to visit the source.