1 84 OILS, PAINTS, AND VARNISHES 



For the sake of ornamentation paints of various colors are in 

 demand. Paints are colored by mixing pigments, or coloring 

 substances, with the white lead and oil. These coloring sub- 

 stances are usually metallic compounds ; for example, Bruns- 

 wick green is a metallic compound made by soaking copper in 

 salt water containing certain sulphates ; yellow ocher is an oxide 

 of iron. Some of the brightest and most beautiful pigments 

 are formed when lead unites with oxygen to form lead oxides. 

 Black paints are usually obtained by stirring lampblack or 

 finely ground charcoal with the white lead and linseed oil. A 

 pigment much used for pleasing effects by photographers and 

 water color artists is sepia. This coloring substance is obtained 

 from a sac in the cuttlefish, and is, in fact, the substance which 

 is thrown out by the fish when it is disturbed, and which 

 serves to blacken the water around the fish. 



The pigments which are stirred into the paints are not dis- 

 solved in the oil, but are suspended in it in a finely divided 

 state. These minute particles are spread with the paint. 

 When the paint dries, they are caught and held in the tough 

 skin, and give color to the surface which the film covers. 



Varnish and shellac. Almost every home has linseed oil 

 with which to rub down dingy furniture, to refinish worn and 

 scratched household articles, and to brighten floors and fixings. 

 When linseed oil alone is rubbed over a surface it dries to a hard 

 tough film and serves as a protection, but it does not give any 

 marked brilliancy to the surface. The protective coating 

 formed by varnish, on the other hand, is brilliant and glossy, as 

 well as hard and tough, and is more desirable for many pur- 

 poses. Varnish is made by putting melted rosin in boiling lin- 

 seed oil. When the mixture has cooled, turpentine is added 

 until the mass becomes thin enough to spread with a brush. 



Occasionally varnish is made by dissolving resin in alcohol. 

 The alcohol evaporates and leaves a brilliant but brittle film 



