USING A PORTABLE SPECTROMETER TO SOURCE ARCHAEOLOGICAL MATERIALS AND TO DETECT RESTORATIONS IN MUSEUM OBJECTS
SARAH U. WISSEMAN, THOMAS E. EMERSON, MARY R. HYNES, & RANDALL E. HUGHES
Infrared spectroscopy has a long history in the field of conservation science in the characterization of many organic and inorganic materials (Derrick et al. 1999). Most of this work has been accomplished using stationary laboratory equipment operating in the mid-infrared (IR) range of the electromagnetic spectrum.
At the University of Illinois, we have been using a portable infrared mineral analyzer (PIMA) that operates in the short-wavelength infrared (SWIR) range to determine the geological sources of stone used to make prehistoric North American figurines and pipes. The PIMA has the advantages that it is nondestructive, portable, and capable of taking quick, 30-second readings. Our research has taken us to both quarry sites and museums to collect PIMA readings of stone outcrops in situ, rock samples collected by geologists and archaeologists, and artifacts in museum collections. Not surprisingly, we have encountered some artifacts in museums that are either not authentic or are partially restored using common materials such as plaster, paint, and shellac. Thus we discovered that PIMA spectroscopy is useful not only in provenance studies that compare source materials with finished artifacts in the museum, but also in distinguishing between original and restored surfaces.
In this article we report on the operation of the PIMA spectrometer and selected applications of this instrument to museum conservation and authentication studies.