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Corrosion and Past“Protective “Treatments of the Benin “Bronzes“ in the National Museum of African Art

Published online by Cambridge University Press:  28 February 2011

Janet L. Schrenk
Janet L. Schrenk*
Affiliation:
Conservation Analytical Laboratory, Smithsonian Institution, Washington D.C. 20560
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Abstract

The Benin (Nigeria) “bronzes“1, like many museum objects have been subjected to a variety of coatings and other surface treatments by museums, dealers and private collectors since their removal from Africa during the British Punitive Expedition of 1897. Today these surfaces are discolored, corroded, saturated with “oils and waxes” and generally do not represent the original West African aesthetic. Corrosion often occurs below the “protective” surface coating, despite the apparent visual stability of the surfaces.

Samples of coatings and corrosion from the Benin “bronzes” in the National Museum of African Art have been examined by XRD, SEM-EDZ FT-IR and CLC. Results include the frequent observation of fatty acid salts of copper and other alloy metals.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 185: Symposium G – Materials Issues in Art and Archaeology II , 1990 , 805
Copyright
Copyright © Materials Research Society 1990

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References

Footnotes

1. The term bronze is used throughout the literature on West African metal objects to denote alloys based on copper. Most of the Benin “bronzes” are brass.Google Scholar

2. Freyer, Bryna, NMAFA (private communication).Google Scholar

3. Indigenous is used to refer to any coatings applied to objects within the traditional setting in Africa, and to differentiate these from coatings applied by museums, dealers and collectors.Google Scholar

4. a)Freyer, Bryna (private communication)Google Scholar; b)Roth, H. ling, Great Benin: Its Customs. Arts and Horrors (Barnes and Noble, Inc. New York, 1968)Google Scholar; c)Bradbury, R.E., Benin Studies (Oxford University Press, London, 1973)Google Scholar.

5. Fagg, William, Hirshhorn Museum Records (unpublished, also private communication).Google Scholar

6. amples were mounted with rubber cement on a glass fiber, placed into Gandolfi cameras, and run on a Phillips PW-1720 x-ray generator with Nifiltered CuX,,, radiation at 40 kV, 20 Ma for 12-30 hours.Google Scholar

7. Samples were carbon coated on carbon stubs, and run on a JEOL JXA-840A Scanning Electron Microscope with a Tracor Northern TN-5502 analytical system. Energy dispersive analysis (EDK) elemental spectra were obtained at 20 Kv.Google Scholar

8. Samples were prepared using a diamond anvil press. FT-IR spectra were obtained using a Spectra-Tech IR-Plan microscope attached to a Mattson Cygnus 100 FT-IR.Google Scholar

9. Samples were hydrolyzed and analyzed using a Hewlett Packard 5830A GLC as described in Erhardt, David, Hopwood, Walter, Baker, Mary, and Endt, David von in Preprints of Papers Presented At the Sixteenth Annual Meeting. New Orleans. Louisiana. June 1-5. 1988 (The American Institute for Conservation of Historic and Artistic Works, Washington D.C., 1988) pp 67–84.Google Scholar

10. Two additional Pitt-Rivers objects have undergone conservation in the NMAFA laboratory, however remnants of the turquoise corrosion and tarry coating remain in the interstices.Google Scholar

11. Chem Services standard (approximately 25% copper palmitate by GLC).Google Scholar

12. Chem Srvices standard.Google Scholar

13. JCPDS, Powder Diffraction File (International Center for Diffraction Data, Swarthmore, PA, 1989) File No. 5–667.Google Scholar