CHAPTER III 

 PAINT PIGMENTS AND THEIR PROPERTIES 



FOR the student of paint technology, who is not already ac- 

 quainted with the chemistry and physics of the various raw 

 pigments which are largely used in the manufacture of paints, 

 the writer advises a careful reading of this chapter, in which the 

 matter has been condensed as much as possible. In order to 

 more thoroughly acquaint the reader with the physical con- 

 stitution of the pigments under consideration, there has been 

 included photomicrographs, which show to advantage the 

 structure of each. 1 



Basic Carbonate-White Lead. This pigment is made by 

 stacking clay pots containing dilute acetic acid and lead buckles, 



By Polarized Light By Transmitted Light 



Basic Carbonate- White Lead 



in tiers, and covering them with tan bark. Fermentation of 

 the tan bark, with subsequent formation of carbon dioxide 

 acting on the acetate of lead formed within the pots, produces 

 basic carbonate of lead. After complete corrosion, the white 

 lead is ground, floated, and dried. Corroded white lead has a 

 specific gravity of 6.8 and contains about 85% lead oxide and 



1 The author gratefully acknowledges the assistance of Dr. J. A. Schaeffer 

 in the preparation of the photomicrographs shown in this chapter. 



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