Several Egyptian bronze artifacts were recently treated by Christina L. Simms, Conservator of Objects, at our Cleveland area art conservation center. These art objects include an Egyptian bronze bowl as well as bronze Egyptian bronze deity statues.
Once buried artifacts can often have layers of thick green or red corrosion, but the corrosion is stable, meaning it will not lead to further deterioration. Sometimes, the bronze metal artifact will develop active corrosion. Copper-based alloys in particular can suffer from a powdery or friable, pale green corrosion. This requires immediate conservation treatment for bronze artifacts since it could indicate “bronze disease”. Advanced bronze disease can appear as a light to dark green liquid, which secretes from the object.
In general, bronze disease is caused by the existence of cuprous chlorides deposits within the metal leading to corrosion, and it is a process that will continue to corrode the bulk metal unless the contaminants are removed. This is not an easy task.
Some of the Egyptian bronze artifacts at our conservation lab facilities did have areas which seemed to be affected by bronze disease. For conservation treatment, the active corrosion was manually removed with a scalpel under magnification to prevent any damage to the underlying metal. The surface was chemically treated to neutralize corrosion, and it was followed with a corrosion inhibition treatment.
The art conservation results created a surface which is relatively unchanged, but the Egyptian bronze artifacts are now stable.