64 ANNUAL OF SCIENTIFIC DISCOVERY. 



The results of trials, similar to those above recorded, proved most satis- 

 factorily that the protective coating resisted to a remarkable degree the 

 action of heat, evinced no symptom of peeling off the highly heated surface 

 of the wood, and protected the fibre to a great degree from the influence of 

 flame playing upon its surface. The durability of the coating was tested by 

 exposing prepared surfaces of wood to a continuous stream of water and to 

 heavy rains for a considerable period. It was found that the rain had no 

 effect upon the coating ; in the other more severe test, the material Avas only 

 to some extent removed, after a time, on that spot where the jet of water 

 first impinged upon the wood. A trial was made of the firmness of the 

 coating, by applying heavy blows to the surface of the wood. The covering 

 was only disturbed in one or two places, where the lime had been laid on 

 rather too thickly. 



The above report was accompanied by a communication relating to the 

 cost of the application of the silicate coating, in which it was stated that, 

 provided the silicate of soda employed has been prepared with especial 

 reference to this application (that is, so as to be readily and completely 

 mixable with water), one pound of the material is sufficient to prepare a 

 surface of wood of ten square feet; while the wholesale price of the silicate, 

 in the form of a syrup, of a certain degree of concentration, is 20 per ton; 

 so that the cost of the silicate required to prepare the wood is at the rate of 

 about two pence for a surface of about ten square feet. 



The following are the directions adopted for general guidance in preparing 

 wood with the coating of silicate of soda and lime. 



The silicate of soda must be in the form of a thick syrup, and the lime 

 wash should be made by slacking some good fat lime, rubbing it down with 

 water until perfectly smooth, and then diluting it to the consistency of thick 

 cream. 



The protective coating is produced by painting the wood firstly with a 

 dilute solution of silicate of soda; secondly, with the lime wash; and lastly, 

 with a somewhat stronger solution of the silicate. The surface of the wood 

 should be moderately smooth; and any covering of paper, paint, or other 

 material, should be first removed entirely, by planing or scraping. A solu- 

 tion of the silicate, in the proportion of one part by measure of the syrup to 

 three parts of water, is prepared in a tub, pail, or earthen vessel, by simply 

 stirring the measured proportion of the silicate with the water, until com- 

 plete mixture is effected. The wood is then Avashed over with this liquid, by 

 means of an ordinary white-wash brush, the latter being passed two or three 

 times over the surface, so that the wood may absorb as much of the solution 

 as possible. When this first coating is nearly dry, the wood is painted with 

 the lime wash in the usual manner. A solution of the silicate, in the pro- 

 portion of two parts by measure of the syrup to three parts of water, is then 

 made ; and a sufficient time having been allowed to elapse for the Avood to 

 become moderately dry, this liquid is applied upon the lime in the manner 

 directed for the first coating. The preparation of the Avood is then complete. 

 If the lime coating has been applied rather too thickly, the surface of the 

 wood may be found, when quite dry, after the third coating, to give off a 

 little lime when rubbed Avith the hand. In that case it should be once more 

 coated over Avith a solution of the silicate, of the strength prescribed for the 

 second liquid. 



