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Details of the Hands

Active corrosion was found to be primarily brochantite, the basic copper sulfate (Cu4SO4(OH)6). A series of comparative cleaning tests showed that the most controllable and efficient removal of both active corrosion and black accretions was by use of an alkaline chelating agent (EDTA) in a water-based paste thickened with a cellulose-based powder. The paste was applied, allowed to stand for as little as 1/2 hour, then removed with water, followed by low pressure steam. After removal of most of the active corrosion and accretions—up to six applications were necessary on some parts of the surface—the sculpture was repeatedly rinsed with water and dried. It was then patinated in two layers, the first a blue-green layer based on copper nitrate, the second a brown/black layer based on ammonium sulfide.

After patination, the sculpture was again thoroughly rinsed with water. A corrosion inhibitor (benzotriazole) was applied hot to a patined surface, followed by a protective coating of wax which was also applied using heat.