BUILDING MATERIALS 169 



paint. The duty of the drier is to carry oxygen to the paint. 

 Driers are usually compounds of lead and manganese, dis- 

 solved in oil, with which are used the standard solvents, 

 such as turpentine or benzine. The quantity of drier should 

 be limited to about 10 per cent, since too rapid drying will 

 tend to produce a surface that will crack. 



Colors. Coloring matter is to be had in several qualities, 

 although in very few pure colors. Black is used in the form 

 of lamp black, bone black, and graphite. The yellows are 

 usually chromate of lead. The green known as chrome green 

 is largely arsenate of copper. The blue known as Prussian 

 blue is ferric-ferrocyanide. Red, violet, and purple are of 

 coal-tar origin. The various shades and tints are obtained 

 by mixtures of the above-named coloring pigments. Among 

 the color substitutes the metallic oxides of iron, such as 

 brown hematite, and brick dust are the most common. This 

 latter differs very little from ochre, except in the degree of 

 burning. 



Paint for inside. Paints for inside work are usually more 

 popular if free from gloss. This condition is easily obtained 

 by the use of less oil and more turpentine in mixing for 

 the proper consistency. 



Ready-mixed paints. Ready -mixed paints are to be had in 

 many varieties and prices. There is a large number of makes 

 of ready-mixed paints which are reliable and will last as long 

 as the "mixed-on-tbe-job" article. The mixed paints are 

 expecially valuable for the floor and porch. It is usually 

 desirable to have a floor paint which will dry quickly, but 

 with an elastic surface. 



Cold-water paints. Cold-water paints are a simple mix- 

 ture of an adulterating base, such as whiting or gypsum, 

 together with some cementing material, such as glue. They 

 are mixed with water and applied in the same way as any 

 other paint. They are inexpensive and not waterproof, 

 but may give a hard and highly satisfactory surface for 

 interior wall decoration. 



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