When students and staff and faculty team up at Beloit College, the results can be more exciting than the latest Indiana Jones flick. Two recent collaborative efforts sought to analyze ancient artifacts through nondestructive means. Using nondestructive techniques is paramount so that researchers can learn as much as possible without causing damage to museum collections.
In the 1960s, Herbert Spencer Zim and Sonia Bleeker Zim gifted a Peruvian “bird mummy” to the Logan.
This one-and-a-half-foot-long artifact consists of cotton cloth and cord wrapped around a stiff bundle with colorful tail feathers coming out of one end. It’s not difficult to imagine a brightly feathered macaw stuffed inside the package with a protruding tail. However, verification seemed prudent and an opportunity to CT scan the bundle presented itself.
Greta Taylor ’18 and radiologist Beth Taylor make the “bird mummy” more comfortable for its CT scan.
Greta Taylor ’18 arranged for us to take the mummy to Centegra Hospital in McHenry, Ill., where the bundle was imaged by radiologists. The nondestructive method of computed tomography (CT) allows us to see inside the bundle without savagely sawing it open. We thought that if there was indeed a bird inside, we’d want to consult with ornithologists to identify the species and determine whether it had traveled over great distances from the Peruvian jungle to the coastal region where this bundle was found. What we saw with the CT scan, however, was a bundle filled with a variety of objects, including a small ear of maize. While images are still being processed, we will soon attempt to identify the dozens of objects inside the bundle. With these new data, we’ll reconstruct where this object came from, what it was for, and who might have been buried with it.
Here at Beloit, we have access to many types of instruments in the Science Center. There are several methods for nondestructive artifact analysis, but a particularly useful and low-cost option for metal objects is pXRF (portable x-ray fluorescence spectroscopy). With the help of Steve Ballou, and with students Alicia Hoffman’15 and Reed Peck-Kriss’15, we took a couple dozen gold, silver, and bronze pre-Columbian artifacts to the Science Center to learn about their composition. This semester, Prof. Quave, Alicia, and Reed have come together to unite their diverse sets of experience and expertise in metallurgy. Alicia is knowledgeable about archaeochemistry and compositional analysis, while Reed has much firsthand experience in metalworking and understands manufacturing techniques. With Prof. Quave’s acquaintance with pre-Columbian culture, they’ve found more holistic and comprehensive results than they would have working alone.
A thin metal ornament in the form of a feline face – check out the whiskers and snout in the photograph -- appeared to be a type of native gold made by depleting the surface of copper. Instead, our pXRF analysis showed it was composed of brass. Therefore, this object is not actually a pre-Columbian ornament, but is rather a convincingly aged and decorated piece made for sale on the antiquities market. Our analyses of other metal artifacts indicate differences in where and by whom they were made, providing us with insights on ancient economies and social organization.
A feline face ornament thought to be made of depletion-gilded gold (tumbaga) turned out to be brass upon nondestructive analysis.
Interdisciplinary and critical inquiry calls into question assumptions that are decades old. Collaborative work between students and faculty and staff offer opportunities for students to learn while doing and to bring together disparate types of experience and knowledge to promote greater understanding. The objects studied here allow us to reconstruct ancient cultures and use multiple non-destructive techniques to give voice to ancient materials in a way that does not compromise their preservation or continued use by future generations of Beloiters.