There are several companies who have processes of treating wood to render it fire-resisting. These processes differ materially. None of them renders the wood absolutely fireproof, and tests have conclusively established that all such treated woods will burn if subjected to sufficient heat for a considerable time. Some authorities place this temperature limit at which ignition will occur, as low as 100° above the temperature required to burn untreated wood. Other authorities claim that the period during which wood will glow after it has been ignited and the flame removed, is as 1 to 10 for the treated and the untreated woods respectively.
The process of treating woods is to impregnate them with certain chemicals which serve to retard the giving off of combus tible gases by the wood under heat, and which also, under the action of heat, themselves give off certain other gases that serve to extinguish combustion when started.
It has undoubtedly been demonstrated that treated wood will burn, and that the gases from it are combustible. It is, however, equally well established that treated wood will not ignite as readily as untreated wood; that it requires a higher temperature to main tain its combustion; and that when the source of heat is removed the wood will cease to glow more quickly than untreated wood.
A material has recently been put on the market in England under the name of "Uralite," which, it is claimed, can be worked like wood ; and can be used largely in the same way, that is, either solid or as a veneer to form a fireproof covering. The basis of the material is asbestos mixed with whiting. The finished material is made of several thin layers felted together. For a description of this material, see August 15, 1902