SCIENCE IN THE INDUSTRIAL WORLD 



charcoal, bones, and smoky lamps charged with foul- 

 smelling oils, as it is from these sources that he makes his 

 wares. 



As most of the forms of carbon found in the mineral 

 world, except the mineral oils, are crystalline in char- 

 acter and hence not available for making the best pig- 

 ments, the vegetable kingdom furnishes the cheapest 

 sources. For production from the latter two general 

 methods are used; one, the process of dry distillation, 

 or heating the substance to be carbonized in the absence 

 of air; in the other the supply of air is restricted. An 

 example of the last method is shown in the soot formed 

 by smoky lamps or defective gas-burners, such soot 

 making the finest forms of black pigment which may be 

 used without further treatment. In the case of the car- 

 bon produced by dry distillation, a good pigment can 

 be produced only by grinding and the addition of oil. 



In the commercial world there are two principal 

 kinds of black pigments, "charcoal" blacks and 

 "soot" blacks. Practically all black pigments on the 

 market, regardless of their commercial or trade names, 

 have one or the other of these two blacks in them. It 

 is possible, of course, to make a fine black from such a 

 substance as ivory; and "ivory black" was formerly 

 made exclusively from this substance. But aside from 

 some of the very finest forms of artists' pigments, little 

 ivory black is now made from ivory, the name indicating 

 the quality rather than the composition of the pigment. 



In making charcoal black the first step in the process, 

 that of making the charcoal, does not differ materially 

 from that of the ordinary process of charcoal-burning. 



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