This oil painting by Georgia O’Keefe called “Pedernal” has zits. Researchers now know why these damaging bumps form. Chemicals in the paint have reacted to form small knobs. GEORGIA O'KEEFFE. PEDERNAL, 1941. OIL ON CANVAS, 19 X 30 1/4 INCHES. GEORGIA O'KEEFFE MUSEUM. GIFT OF THE GEORGIA O'KEEFFE FOUNDATION. © GEORGIA O'KEEFFE MUSEUM [2006.5.172]