PAINTS, DYES, AND VARNISHES 



the natural product, ground and levigated. Burnt 

 umber, which has a darker and warmer color than 

 the raw mineral, is made by heating the natural umber 

 to a red heat. 



Chemically, umber is a very complex substance, 

 specimens from different sources showing considerable 

 variation in this respect. Among its components are 

 silica, manganese, aluminum, calcium carbonate, ferric 

 oxide, and barium sulphate. The color of umber is per- 

 manent; it mixes well with other pigments, and for 

 these reasons, and because of its cheapness, it is a favorite 

 with painters and artists. 



Vandyke brown is a pigment made from several 

 natural deposits, some of them of peaty origin, and 

 named after the great Dutch painter on account of his 

 fondness for brown colors. It is also manufactured 

 from the cuttings of cork that have been calcined. The 

 common Vandyke browns for sale in the market are 

 usually mixtures of some black pigment, such as lamp- 

 black, with red oxide of lead and yellow ochre. They 

 are good pigments, however, mixing well with other 

 colors, and being practically permanent tinder all 

 conditions. 



PIGMENTS FROM VEGETABLE AND ANIMAL SOURCES 



Generally speaking, it may be said that the pigments 

 from animal and vegetable sources are of greater im- 

 portance than those of mineral origin to the dyer, while 

 to the painter the reverse is the case, although there 

 are certain pigments from every source of great 



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