PAINTS, DYES, AND VARNISHES 



some medium. Thus a stain or dye enters into intimate 

 combination with the wood or the fabric to which it is 

 applied. Being transparent it does not conceal the 

 grain of the wood or the fibers of the cloth that it 

 colors, and does not increase its thickness to any ap- 

 preciable depth. A paint, on the other hand, simply 

 covers and conceals the underlying structure by an 

 appreciable layer without becoming an integral part of 

 it. This is shown in the familiar example of paint 

 peeling off wood, leaving the original surface exposed. 



A varnish is essentially a transparent paint, rather 

 than a stain. Color effects may be produced very much 

 the same as in the case of stains by incorporating a 

 transparent pigment in the varnish; but it is possible for 

 a varnish to peel off from an underlying surface, just as 

 in the case of a paint. 



In speaking of the various paints their "covering 

 power" will often be referred to. This should be under- 

 stood as meaning the amount of surface that a pigment 

 will conceal with an opaque layer. This quality is often 

 determined by the size of the individual particles of the 

 opaque pigment, the smaller the particles the greater 

 the covering power, generally speaking, a rule, how- 

 ever, that is subject to many exceptions. 



The processes in paint manufacture known as 

 "grinding," "filtering," "precipitating," etc., are suf- 

 ficiently self-explanatory without going into details 

 here. What is known as "levigation," however, needs 

 fuller explanation. 



The principle of the process of levigation depends 

 upon the fact that the larger particles of a substance, or 



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