MECHANICS AND USEFUL ARTS. G3 



OX THE PROTECTION OF WOOD FROM FIRE. 



The attention of practical men has been for some years past directed, from . 

 time to time, to the importance of affording to wooden erections some degree 

 of protection from the effects of fire; and numerous plans have been pro- 

 posed, and to some extent tested, for lessening the combustibility of wood, 

 and for covering its surface with a protective coating more or less unalterable 

 by fire. 



The simple application of lime or clay wash, for example, has been found 

 to afford some slight protection to wood, although the tendency of such 

 materials to peel off the surface of the wood (into which they do not in any 

 way penetrate), by exposure to heat, and the rapidity with which the 

 coating is destroyed by atmospheric influence, render them very ineffective 

 agents. 



The successful results obtained by the application of alkaline silicates, as 

 protective materials, has recently induced the English War Department to 

 institute an examination, with a view of testing the comparative value of 

 the cheapest of these, the soluble silicate of soda, as an agent for decreasing 

 the combustibility of wood. 



The property possessed by the soluble alkaline silicates, of being readily 

 softened by hot water, and thus converted into a state of solution, while 

 they are but slightly affected by cold water, renders their application to 

 wood, either in the form of a bath, or as a wash, very simple. Their dilute 

 solutions being readily absorbed by wood, the surfaces of the latter, as it 

 dries, assume the form of a hard coating. 



From the official report, we dei'ive the following extracts, descriptive of 

 the results arrived at, by employing silicate of soda. 



" Various specimens of dry wood were prepared with silicate of soda, by 

 being soaked for a few hours in a weak solution. Upon examining the 

 interior of these, after removal from the bath, and subsequent desiccation, 

 the silica was found to have penetrated about a quarter of an inch on all 

 sides. On piling the above over a fire, together with specimens of unpre- 

 pared wood, and others that had been prepared by different processes, the 

 superiority of the silicate of soda, as a protective agent, was fully demon- 

 strated. Some specimens were then simply painted with a moderately 

 strong solution of silicate; and afterwards placed, together with unprepared 

 wood, in a pool of coal-tar naphtha, and the naphtha ignited. The result 

 was, that while the unprepared Avood was speedily consumed, the wood 

 coated with silicate was only scorched, but not burned." 



Shortly after the experiments above described were made, the possibility 

 suggested itself of rendering the coating of silicate less destructible by 

 exposure to wet, of increasing its efficiency as a protective, and of rendering 

 its application more economical by combining with its use that of ordinary 

 lime wash. 



Some pieces of plank were prepared in the following manner: a dilute 

 solution of the silicate of soda was first applied with a brush ; when this 

 had thoroughly soaked into the wood and dried, a thick lime wash (made 

 by slaking some lime, and reducing the hydrate to a smooth wash of the 

 consistence of thick cream) was applied; and, lastly, after the planks had 

 been exposed to the air for two or three hours, they were painted with a 

 second solution of silicate of soda, somewhat stronger than that first used. 



