The Application of X-Ray Fluorescence (XRF) Spectrometry in the Characterization of Glass Degradation in Beaded African Art

The utility of X-ray fluorescence spectrometry in the study of stable and degraded glass as well as coatings applied to ethnographic costume is discussed. South African Ndebele costume and ceremonial regalia were studied from the collection of the National Museum of African Art, Smithsonian Institution, as part of a larger condition survey of the entire beaded collection. The susceptibility of certain types (i.e., colors) of glass beads was noted as well as the presence of a potentially indigenously applied coating which appeared to interact chemically with unstable glass beads. Potentials and limitations of XRF in glass compositional analyses, coating identification and detection of pesticide residue on ethnographic art are discussed. In 2009, a study was undertaken of beaded costume and sculpture at the Smithsonian Institution’s National Museum of African Art (NMAfA). The project’s goal was to document the conservation issues particular to African beaded art as evidenced in one major collection. To our knowledge there has been no large-scale investigation of bead degradation specific to African art. Most conservation-related literature focuses on Native American and western beaded art and costume (e.g., Fenn 1987; Carroll and McHugh 2001; Lougheed 1986; Sirois 1999). The NMAfA collection is comprised of more than 10,000 objects, over 500 of which are beaded. The study focused exclusively on beaded costume and sculpture, ignoring sparsely beaded objects such as wooden sculptures adorned with bead necklaces. The overall condition of the NMAfA beaded collection was assessed. The stability of glass beads was of particular interest given that beads are known to have problems in other collections. It was a priority to note trends in the susceptibility of certain object types, material combinations, or amongst cultural groups. Three hundred and forty-four pieces of beaded sculpture and costume from 24 different African cultures were condition surveyed. Trends in degradation were documented both in the stability of certain component parts and amongst cultural groups. Substrates and stringing mechanisms were generally stable. In contrast, glass degradation posed a distinct problem: 17% of the surveyed glass beaded collection exhibited glass deterioration. Furthermore, it was found that the majority of these deteriorating objects (78%) originated from two African regions — two cultural groups in Cameroon (the Bamum and Mandara Mountain groups) and the Ndebele of South Africa. Continued on page 3