VARNISHING. 



linseed-oil for a few minutes, and strain it. Use 

 it warm. 



Essential Oil Varnish. 



The essential varnishes consist of a solution of 

 resin in oil of turpentine. This varnish being ap- 

 plied, the turpentine evaporates, leaving the resin 

 behind. They are commonly used for pictures. 



To dissolve Gum Copal in Oil of Turpentine. 



Whatever quantity is to be dissolved should be 

 put into a glass vessel capable of containing at 

 least four times as much, and it should be high in 

 proportion to its breadth. 



Reduce two ounces of copal to small pieces, and 

 put them into a proper vessel. Mix a pint of oil 

 of turpentine with one-eighth part of spirit of sal 

 ammoniac j shake them well together, put them to 

 the copal; cork the glass, and tie it over with a 

 string or wire, making a small hole through the 

 cork. Set the glass in a sand heat, so regulated as 

 to make the contents boil as quickly as possible, 

 but so gently, that the bubbles may be counted as 

 they rise from the bottom. The same heat must be 

 kept up exactly till the solution is complete. 



It requires the most accurate attention to suc- 

 ceed in this operation. After the spirits are mixed, 

 they should be put to the copal, and the necessary 

 degree of heat be given as soon as possible. It 

 should likewise be kept up with the utmost regu- 

 larity. If the heat abates, or if the spirits boil 

 quicker than is directed, the solution will immedi- 

 ately stop, and it will afterwards be in vain to pro- 

 ceed with the same materials j but if properly 



9 

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