A Peruvian funeral cortege in the Krannert Art Museum (KAM) was recently studied by ATAM at the invitation of former curator Eunice Maguire.
The artifact belongs to the Chancay-Chimu cultures and dates to about 1400 A.D. It is constructed out of a silver-copper sheet-metal, fastened to a formerly blue, textile-covered mat. Represented in the cortege are several figures of presumably different ethnic backgrounds, each originally wearing characteristic clothes and headdresses of colored cloth and feathers. Good parallels for this cortege are hard to find in metal but do exist in clay form.
The research team was interested in the composition of the metal alloy used to make the artifact, the different joining techniques employed, types of surface corrosion, and the content of the hollow casket. The curator's primary concern was the nature of the blue-green corrosion on several pole-ends and headdresses. Is this a stable form of corrosion, or is it "bronze disease" requiring immediate conservation treatment?
The cortege was X-rayed by Richard Keen at the Large Animal Clinic. The X-rays show how the sheet metal was folded along joins, thickened join areas where some kind of solder was used, and how the ancient artifact was fastened to a modern board using modern threaded bolts. The content of the casket is two vases and pillow, as expected from visual examination.
Tiny flecks of corrosion were taken from the blue-green areas of corrosion in several areas.
Unfortunately, the specimens obtained were too small for some types of analysis. Mauro Sardela of the Materials Research Laboratory attempted X-ray diffraction, but was unable to get a valid spectrum. ATAM's new PIMA spectrometer was more successful because the technique is totally non-destructive and the reading was taken from the back of one headdress-a much larger area of corrosion than could be sampled without damaging the artifact.
Since the PIMA spectrum did display significant features of atacamite, a copper chloride typical of "bronze disease," the team recommended conservation treatment in the near future. This result was later verified by Pankaj Sarin (Materials Science), using energy-dispersive X-ray spectroscopy (EDS).
The KAM cortege has traveled to New York to be part of an exhibit on ancient Peruvian silver at the Metropolitan Museum of Art during 2000-2001.