THE LIGHTEST WOOD IN THE WORLD.

Otago Witness, Issue 3509, 14 June 1921, Page 52

THE LIGHTEST WOOD IN THE WORLD.

Balsa, the trojiical wood lighter than cork is now on the American market for a variety of special uses that require buoyancy, non-conductivity for heat, smoothness, softness and lightness, and speed in working. Balsa is, so far as known, the lighest wood that grows. It averages in weight about one-third less than cork. Ibis lightness results from its peculiar cellular structure, which is said to differ from that of any other wood. The cell walls are extremely thin ; and where ordinarily there are woody fibres, there is in balsa practically no lignification. This structure coniines within its large, barrelshaped cells a quantity of “dead” air, which represents 92 per cent, of the total volume of the wood and which accounts for its remarkably high insulating value. In its natural state of preservation by painting or otherwise, are ineffective iii preventing deterioration. After extended experimentation in the treatment of balsa, a process of wood preservation has been developed which meets the requirements of balsa and its uses, giving adequate protection and permanency of quality to the wood. This process thoroughly impregnates all parts of the wood with a thin coating which does not appreciably increase its weight. Treated balsa is waterresisting and is not subject to the attacks of insects or the bacteria of decay. Combined with its light weight and its quality of insulation against heat, balsa possesses a structual strength which, pound for pound, is greater than that of any wood. In actual test, balsa shows a strength per square inch fully one-half the strength of spruce.

Extensive tests have shown that balsa has an insulating efficiency at least equal to that of any other commercially used product. The heat conductivity of water is such that very small percentages of moisture absorption greatly lower the quality of an insulation. Balsa is so thoroughly waterproofed that its original efficiency is maintained. Treated and waterproofed, balsa is now being used, we are told, as insulating material for refrigerated sjwces in over 50 ships. Tiie early extension of its industrial use to refrigerator-cars and trucks is expected, as well as to all insulated compart ments, from small parcel-post boxes for foodstuffs, etc., to cold-storage warehouses Insulation is, however, only one of the many uses to whinch balsa has already been put. and further study of its properties is constantly disclosing new directions in which it will prove of value. The writer goes on : “Balsa first attracted attention by reason of its light weight, which suggested its uses in life-preservers and other equipment for saving lives at sea. During the war, large numbers of balsa rafts, elliptical rings of solid, treated balsa, waterproofed and covered with canvas, were a familiar part of the safety equipment carried on board the American transports. Balsa fenders are used on two types of lifeboats. The great buoyancy of this wood has also been made use of in a line of water sporting goods, such as surf boards and decoys. “Excellent proof of the effectiveness of the waterproofing treatment was shown during the war by the 70.000 mine-buoys whoso use largely made possible the 250mile ‘mine barrage' across the North Sea. This was said 1o be the onlv type of float which could withstand the long submersion and the crushing effect of depth charges. “Of the miscellaneous uses dependent upon its light weight, balsa has already been successfully employed in the construction of hydroplane pontoons and for filling out stream-lines of airplane struts. “The smoothness and softness of baba have led to its inereasinging vise in the protection during shipment of highly finished furniture surfaces, such as phonographs and pianos. N< t only is the woo l smooth. but it has remarkable elasticity, and this is not in the least altered by subsequent compressions. “The facility and speed with which treated balsa may be worked either by hand or with wood working machinery have made is particular!v adaptable to use in toy manufacture, such as toy airplanes. Tt has also been used for the throats of phonographs, which in certain makes must be hand-carved.”