PAINT PIGMENTS AND THEIR PROPERTIES
For the student of paint technology, who is not already acquainted 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 constitution of the pigments under consideration, there has been included photomicrographs, which show to advantage the structure of each.[12]
[12] The author gratefully acknowledges the assistance of Dr. J. A. Schaeffer in the preparation of the photomicrographs shown in this chapter.
Basic Carbonate-White Lead. This [pigment] is made by stacking clay pots containing dilute acetic acid and lead buckles, 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 15% of carbon dioxide and water. Its opaque nature and excellent body renders it extremely valuable as a constituent of paints. Checking and chalking progress rapidly when the pigment is used alone. The various sized particles, both large and small, resulting from the corrosion process, are prominently shown in the photomicrograph.
Crystals of Cerussite in Old Dutch Process White Lead. (Greatly magnified)
