AN EXAMINATION OF THE PATINA AND CORROSION MORPHOLOGY OF SOME ROMAN BRONZESDAVID A. SCOTT
ABSTRACT—The Roman bronze statues of Togati, Roma, and Venus (Demeter) and in the collection of the J. Paul Getty Museum were subject to a detailed technical study. Of particular interest are their unusual, matte, and finely preserved patinas, which closely parallel another bronze, the Nike, in the Cleveland Museum of Art. The bronzes, which date to A.D. 40–68, are described and analyzed and an account of their corrosion is given, drawing on the early work of W. von Geilmann, who examined the corrosion of bronzes from sandy soils in Germany. The patinas of these objects contain substantial amounts of tin oxide and also display warty corrosion. It was postulated, and confirmed by analysis, that patinas of this kind should contain no chloride ions; thus, there are at least two types of warty corrosion of ancient bronzes. The first type, as here, is chemically stable and does not necessarily require strictly regulated humidity conditions. The second type of warty corrosion is related to the presence of chlorides, usually with an accumulation of cuprous chloride. The three bronzes studied here are closely related and are almost certainly from the same burial deposit, as evidenced by their associated soil and minerals. These materials were not completely cleaned from the surfaces of the bronzes, so essential information regarding their origin was preserved. Cleaning during conservation to a uniform “original surface” or “marker layer” would have removed this important evidence.
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