Balsa wood is very soft and light, with a coarse, open
grain. The
density of dry balsa wood ranges from , with a typical density around . Balsa is the softest wood ever measured using the
Janka hardness test (). The wood of the living tree has large cells that are filled with water. This gives the wood a spongy texture. It also makes the wood of the living tree not much lighter than water and barely able to
float. For commercial production, the wood is kiln-dried for about two weeks, leaving the cells hollow and empty. The large volume-to-surface ratio of the resulting thin-walled, empty cells gives the dried wood a large strength-to-weight ratio because the cells are mostly air. Unlike naturally rotted wood, which soon disintegrates in the
rainforests where balsa trees grow, the cell walls of kiln-
seasoned balsa wood retain their strong structure of
cellulose and
lignin. Because it is low in density but high in specific strength (strength per weight), balsa is a very popular material for light, stiff structures in
model bridge tests, model buildings, and construction of
model aircraft; all grades are usable for airworthy
control line and
radio-controlled aircraft varieties of the aeromodeling sports, with the lightest "contest grades" especially valuable for
free-flight model aircraft. However, it is also valued as a component of full-sized light wooden
aeroplanes, most notably the
World War II de Havilland Mosquito. Balsa wood is often selected as a core material in
composites. Because balsa grows quickly and tolerates poor soils, it is lower in cost per performance compared to polymer foams like
EPS while having better tensile strength than typical foams. For example, the blades of
wind turbines are commonly constructed of many balsa plywood cores and internal spars covered with resin infused cloth on both sides. In
table tennis rackets, a balsa layer is typically sandwiched between two pieces of thin
plywood made from other species of wood. Balsa wood is also used in
laminates together with
glass-reinforced plastic (
fibreglass) for making high-quality balsa
surfboards and for the
decks and topsides of many types of
boats, especially pleasure craft less than in length. On a boat, the balsa core is usually
end-grain balsa, which is much more resistant to compression than if the soft balsa wood were laid lengthwise. More than 90% of the world's Balsa wood volume is prepared into end grain panels for the composites industry, mostly used as structural cores in the wind turbine blades, where strength, rigidity, durable and environmentally sustainable materials are sought after. Balsa is also used in the manufacture of "breakaway" wooden props such as tables and chairs that are designed to be broken as part of theatre, movie, and television productions. The
fifth and
sixth generations of the
Chevrolet Corvette had
floor pans composed of balsa sandwiched between sheets of
carbon-fibre reinforced plastic. Balsa wood is also a popular wood type used in the arts of
whittling, == Gallery ==