Balsa

Balsa

Balsa

Colour

Durability

Density in kg/m3

Balsa

The Tree
Balsa is a rapid growing tree with a very short life. It often attains a height of 21.0m and a diameter of 0.5m in 7 years, and on good sites slightly larger dimensions in 5 years. After 8 years. the heart tends to develop a pink colour which is inferior to the sapwood. The trees reach maturity in 12 to 15 years, after which they deteriorate rapidly, growth slows, the heartwood becomes waterlogged and doty, and the new growth is hard and heavy.

The Timber
Balsa is the lightest and softest timber used commercially. It possesses an unusually high degree of buoyancy and provides very efficient insulation against heat and sound; where these properties are essential, the wood is adaptable to a great number of special uses. The best balsa is almost white in colour with a lustrous surface; the grain is open and straight. It varies greatly in weight, sometimes from 120 kg/m3 at the centre of the log to 340 kg/m3 near the outer edge. However, wood cut for export generally weighs from 128 kg/m3 to 224 kg/m3 with an average weight of 160 kg/m3 when dried.

Drying
Balsa is extremely difficult to air dry from the green condition. In Ecuador, end racking is practised, and stock 100mm thick dried to below 20 per cent moisture content in 14 to 21 days. It has been reported that heavy degrade sometimes accompanies this rapid drying. In Puerto Rico, 25mm stock air dried under cover in stickered piles, dried to 17 per cent moisture content in 4= months with moderately heavy degrade in the form of cupping, bowing and twisting, and very slight surface checking. Kiln drying requires great care to avoid warping, splitting, case-hardening, and 'toasting' the wood. Once the wood is dry, it is stable in use; changes in atmospheric conditions cause only minor shrinkage or swelling. Green, freshly cut balsa generally contains from 200 to 400 per cent moisture. Soaked specimens have been recorded at 792 per cent moisture. To overcome this tendency to soak up moisture, balsa is often given water-proofing treatments with paraffin wax, water-repellents, water-repellent preservatives, varnish, or paint.

Strength
For its weight, balsa is a strong timber, but in comparison with European redwood (Pinus sylvestris), balsa has about half the strength in bending and stiffness and about 70 per cent the strength in compression parallel to the grain. It is about 40 per cent weaker in bending, and 20 per cent less stiff than obeche (Triplochiton scleroxylon). The heartwood of balsa has only half the strength of the sapwood.

Working Qualities
Good - Very easy to work with sharp, thin-edged power or hand tools and has practically no dulling effect on cutting edges. It takes nails and screws readily but owing to the softness of the wood does not hold them well. Gluing is the most satisfactory method for fastening or holding the wood in use. It can be stained and polished but it absorbs much material used in the process.

Latin Name
Ochroma pyramidale, Ochroma lagopus, Ochroma bicolor

Also known as
Guano (puerto Rico and Hondutas), Ianero (Cuba), polak (Belize and Nicragua), topa (Peru), tami (Bolivia)

Wood Type
Hardwood

Treatability
Difficult

Moisture
Small

Texture
Fine

Origin
Cuba, Trinidad, Mexico, Central America, Brazil, Bolivia, Peru, Ecuador, Venezuela, Belize, Guatemala, Honduras, Nicaragua, Costa Rica, Panama, India, Indonesia