PRESERVING TIMBER.

Taranaki Daily News, 16 July 1919, Page 6

PRESERVING TIMBER.

WHAT HAS BEEN BONE HI DENMARK. Good results have been obtained in Denmark by impregnating pine and beech with tar-oil. A number of heavy piles driven in 1902 were in 1912 found still saturated with oil and in perfect condition, while' unimpregnated timber was entirely destroyed by pile worm. The State railways therefore now dehand ihat all timber used for marine purposes mus.t be impregnated with taroil. It hits been found possible to impregnate the heartwood of good pine timber, as the cells are already filled with resin, but it is important that the sap wood is uniformly saturated with oil and protected against attacks by pile-worms. Piles are therefore specified to be unsawn, completely unstripped of bark, and scraped free from all bast. Timber to be impregnated is enclosed in a steel cylinder large enough to contain the longest piles, and is first sob-, jected to a vacuum continued until all moisture is extracted, when heaw coal tar-oil at a high pressure is pumped into the cylinder. The specific gravity of the oil must not be less than 1.04 nor more than 1.10, with an evaporation not exceeding 25 per cent of its volume when heated at 482deg.F. Light oils are not suitable. The quantity absorbed by pine-wood is 11J ,to 1211b per cubic foot. * Beech wood is gene/ally impregnated in two stages, and will absorb 12yb W 221b of oil per cubic foot. It is valuable for marine work, being very durable, but cannot be obtained of sufficient length for piles, and its use is confined to planks for covering the projecting porios of piles, and for bulwarks, s.teps and shipways.