Wood Preservation 



phant, solution of the problem than ever before. Decay is some- 

 thing that enters wood from the outside, at some time. To 

 prevent the entrance of the spores of the disease into sound 

 timber is to save it, A protective covering that will effectively 

 do this is the quest of science and of all the wood-consuming 

 industries. One of the earliest hints came to men before the 

 days of Plato and Aristotle. The lasting qualities of charred 

 wood were observed. So they learned to char the lower parts of 

 all stakes, posts and poles before setting them in the ground. 

 The ancient practice is still held to in many regions. The timbers 

 in salt mines last indefinitely. So the suggestion to soak posts 

 in brine has been eagerly followed. But the salt soon leaches out 

 in contact with soil water. Impregnation of timbers with chemi- 

 ::als has been practised commercially for about one hundred 

 years. Numerous preparations and processes have been tried 

 with varying success. Chloride of zinc and of mercury, sulphate 

 of iron and of copper, and other things have had their advocates. 

 Most of them fail because the preservatives are lost to the sur- 

 rounding soil or water, in a short time. Some are too expensive 

 to be practical. Impregnation by soaking, steeping, boiling 

 and pressure has been tried. High temperature, while it produces 

 thorough impregnation, has a disintegrating effect upon the wood 

 fibres as a whole. Soaking takes too much time. Pressure 

 requires elaborate and expensive machinery. Each seems to 

 have its drawbacks. 



Creosote oil, a by-product of illuminating gas, is believed now 

 to be the best substance available for impregnation, and the 

 following the best method of treating the tim.bers. Seasoned 

 railroad ties are placed in a tank in the hot oil until a high temper- 

 ature is reached. The oil is drawn off, and a cold supply pumped 

 in. The sudden cooling and condensing of gases and vapour in 

 the wood cells produce a vacuum suction, to which is added the 

 force of capillarity. Thus oil is forced into the wood. 



Creosote oil has the following good points: (i) It fills the 

 cells with oil, thus keeping water out. (2) It does not leach or 

 lose strength in water or soil. (3) It is a fungicide, and is also 

 poisonous to boring insects and crustaceans, like the white ants, 

 the ship worm, and the Limnoria, creatures that honeycomb 

 furniture, ship bottoms and wharves, giving no visible warning 

 until the structure is a wreck. Creosote prevents the rusting of 



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