SCIENCE IN THE INDUSTRIAL WORLD 



three things the care in making, the quantity of the 

 ingredients, and their quality. It is needless to say 

 that the best varnish cannot be made except from 

 carefully selected resins, carefully prepared and re- 

 fined oil, and highly refined turpentine. Everything 

 else being equal, the relative amounts of these sub- 

 stances determine the kind, rather than the quality of 

 the varnish. 



The best representative of the spirit varnishes, and 

 the one used preeminently in commerce, is shellac 

 varnish. It is simply shellac resin dissolved in alcohol 

 a process requiring no heat, and no manipulation, 

 although stirring hastens the process. The proportion 

 of alcohol to the resin varies within wide limits, but in 

 this country the usual proportion is about one part resin 

 to one and a half parts alcohol. In this mixture there 

 is not a complete solution of all parts of the shellac resin, 

 as a waxy substance seems to be held in suspension. 



When a thin layer of shellac varnish is spread over 

 a surface the alcohol evaporates almost immediately, 

 leaving a thin, impervious film of shellac resin and wax. 

 On account of this quick-drying quality shellac varnish 

 is most convenient for any purpose. The drying takes 

 place so rapidly that several coats may be applied in a 

 very short time; but curiously enough, if too many 

 coats are applied at short intervals, a thick, rubbery film 

 is formed that does not harden completely even after a 

 long time. It is good practice, therefore, not to apply 

 more than two or three coats without allowing some 

 little interval for drying. 



Damar varnish, the type of varnish made by dissolving 

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