PAINTS, DYES, AND VARNISHES 



facture of this product constitutes an enormous industry. 

 The apparatus for its manufacture consists essentially 

 of a chamber in which the substance rich in carbon 

 can be burned at the lowest possible temperature, and 

 some arrangement for catching the carbon and separa- 

 ting it from the products of combustion. The primi- 

 tive apparatus used in the pine regions, where the roots 

 of pine trees are utilized for making soot black, is the 

 same in principle as the more perfected apparatus de- 

 veloped from it. It consists of a low flue built of ma- 

 sonry, connected with which is a long wooden pipe. 

 This pipe is lined with coarse cloth in order to give a 

 rough surface upon which the soot is deposited. A 

 brisk fire of dry wood is first started and kept up until 

 the flue is thoroughly heated so that there will be little 

 tendency for the soot to be deposited there and later 

 consumed by accidental overheating. When the flue 

 is thoroughly heated, pine roots and resinous chips are 

 introduced and burned slowly, a dense, black smoke 

 issuing from the tube as an indication of the state of 

 combustion. 



Keeping such an apparatus at the right working 

 temperature requires much skill, experience, and vigil- 

 ance, as the workman has nothing but his natural senses 

 to guide him. If the fire is too active there is likely to be 

 combustion in the tube, and a loss of soot black, where- 

 as if it is allowed to get too low a very poor product 

 is obtained. The condition of the flame is regulated 

 by the admission or exclusion of air in the flue, the ap- 

 pearance of the flames indicating whether the amount 

 of air is right or not. The ideal condition is difficult 



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