DOES CHARRING TIMBER PROMOTE DURABILITY?

Otago Witness, Issue 1861, 22 July 1887, Page 7

DOES CHARRING TIMBER PROMOTE DURABILITY?

The general belief has long been that it does, and in accordance with this conviction the practice has been widely followed. But a contrary view of the subject is taken by Wood and Iron. That journal says in a recent issue : —

"As charcoal would endure for ages in places where timber would decay speedily, the practice of charring the surface of fenceposts and other timber has been repeatedly recommended in books and ephemeral publications, as eminently worthy of. universal adoption. "The theory. upon which such a recommendation is based would seem to warrant a confident expectation of satisfactory results in practice, but repeated experiments with charred timber have furnished conclusive assurance that the process will not promote its durability. Indeed, numerous experiments have shown that charring promotes premature decay. Two posts split from the same log may be set side by side in the ground, the surface of one being charred and the other not, and it will be seen that the charred post will perish before the other. " The same is true of railroad ties and all such timber as may be exposed to the altering influences of wet and heat. Could the entire timber be changed from its perishable condition to one solid piece of charcoal, the durability would be promoted to a surprising length of time, but the strength of the material would be destroyed. When fence posts or other sticks of timber are exposed to the rapid action of wet and heat, the surface will decay first. One might suppose, therefore, that when timber is enveloped by a layer of charcoal, the durability of the entire piece would be greatly promoted. And such would be the case were it not for the fact that the charcoal is not impervious to water ; and as water reaches the timber below the charred surface, decay will commence soon after the grain of the wood has been exposed to the influences of the weather. When the change has once begun beneath the charred surface, the durable covering of coal will be of no service whatever in preserving any portion of the wood. Taking this practical view of the subject, it. will be perceived that if only half an inch of the outside of a post be charred the post will not endure so long as if the same thickness of wood had been left uncharred to waste away by slower decay."