Analysis of the Benin “bronzes” in the National Museum of African Art

Janet L. Schrenk

Abstract

The Benin brasses and bronzes of the National Museum of African Art, Smithsonian Institution, like many metal objects have been subjected to a variety of treatments by museums, private collectors and dealers during the past ninety years. Today, the surfaces are discolored, corroded, saturated with “oils and waxes”, and generally do not represent the original West African aesthetic. Corrosion often occurs actively below the “protective” surface coating, despite the apparent visual stability of many of these surfaces. An understanding of the nature of both the original and the altered surface is essential for making appropriate treatment decisions and for the development of new treatment methods.

The results of current research being conducted to determine how the “investment material”, surface coatings and other treatments applied to West African metal objects modify/deteriorate these surfaces will be presented. This is being accomplished through study of historical documentation, visual observation of surface features and analysis of the chemical composition and the physical structure of the Benin “bronzes” including the base metal, the “investment material”, coatings and other applied surface treatments, and corrosion products. Corrosion products identified include the fatty acid salts of copper and zinc. The information present will ultimately be used to examine issues and methods for the conservation of these and other copper alloy objects, their long-term stability, and their treatment aesthetics.