Behind the Scenes: Analysis of a Face Jug

The exhibition Face Jugs: Art and Ritual in 19th Century South Carolina, on view this past summer at the Milwaukee Art Museum (and currently on tour through South Carolina, Alabama and Georgia), provided us at Chipstone with a rare hands-on research opportunity.

As you may have read in one of my previous blog posts on Face Jugs, the objects in the exhibition were made by slaves, and later free African Americans, in the Edgefield County of South Carolina from about 1860 to about 1880. Previous scholars posited arguments that connected the face jugs back to Africa, but there was still research to be done in terms of the face jugs’ origin and function.

In addition to conducting our own research, we teamed up with anthropologists, archeologists and historians in order to gain a fuller understanding of the face jugs’ story–and got up close and personal with the objects in the process.

The exhibit consisted of 23 early face vessels, 20 of which were borrowed from institutions and collectors. Seeing them together in the exhibition’s face jugs wall, above, left a powerful impression. We realized that having these many early face jugs together was an amazing chance to further our understanding of the vessels. No one had been able to physically compare and contrast this many face jugs before. We thus set out to study these objects and gather as much empirical data as was possible.

Jon Prown, Executive Director of Chipstone, and I immediately talked with Dr. Mark Newell, an archeologist who, with April Hynes, contributed to the show. We wanted to see if he was interested in coming up with a plan for a series of non-invasive tests that would provide useful data on the face jugs. Mark jumped at the opportunity and wrote out a proposal.

There were a few things we had to do before we could run these tests. First, we worked with the Museum so that the tests could take place in their Conservation Lab, since such tests need to be done in a highly controlled environment. Then we contacted all of the lenders to ask permission to conduct the non-invasive tests and take measurements of their vessels. After all of the lenders agreed, a date was set for the analysis–there was a very small window of time after the show came down and before it had to be packed and shipped to its next venue.

We assembled a face jug analysis team to conduct the tests. This included Jon Prown; Dr. Mark Newell; Terri White, Milwaukee Art Museum Associate Conservator; Megan Narvey, the Museum’s conservation lab intern; Dr. George Calfas, archeologist; Dr. John D. Richards, material scientist; Michelle Birnbaum, doctoral candidate; Jim Witkowski, a collector; and me.

On the morning of August 7, we all met in the Conservation Lab. We set up different stations around one of the lab tables, and Terri and Megan brought one vessel over at a time. Each was weighed and then photographed from different views. The jug (or cup, or pitcher) was then pass on to Mark and me, where it was measured. These measurements included height, shoulder width, diameter, eyebrows, eyes, nose width and height, mouth width and height, neck width and height, and ear width and height. We also made notations regarding neck type, teeth type and whether the vessel had applied tragus (the small knoblike piece of flesh that sticks out in the middle of the ear). Jim added aesthetic observations for each vessel such as inscriptions, whether the eyes were glazed, and the type of handle.

John Richards and Michelle Birnbaum brought a pXRF device for the University of Wisconsin-Milwaukee to do non-invasive material analysis of the clay and glazes. pXRF stands for “Portable X-Ray Fluorescence” device. Since I am not a scientist, I had to look up exactly what that means!

According to the Field Museum, pXRF is “a technique for chemical compositional measurement in which X-rays of a known energy are directed towards a target on a sample, causing the atoms within the material to emit fluorescent X-rays at energies characteristic of its elemental composition.” In other words, it tells the person using the device what exact elements the clay and the glaze are made out of.

This is very valuable, as it can tell us which face jugs might have been made at the same location, since the chemical composition of the clay and the glaze would be the same.

If you’re interested in learning in greater detail the specific process for using pXRF on the face jugs, Dr. John Richards explains it best: “The general protocol we use for ceramic materials relies on multiple reading of 180 seconds each taken at multiple sites on the sample. The analyzer is calibrated to a standard reference sample prior to each session and again at the end of the session as a final reading. We typically target the elements between Fe and Mo on the atomic scale. With clay sources we can also run a second set of readings that target light elements from Mg to Sc. The raw spectrographic data is converted to net intensities using Bruker’s ARTAX software and exported as a text file. Currently, we are using the ‘R’ statistical package to normalize the data and test the individual readings for statistical validity by calculating Mahalanobis distance values. The data set is then examined using a variety of multivariate approaches including PCA, ANOVA, and clustering, and visually examined in a series of biplots.”

The data collected is currently being analyzed by John, Michelle and Dr. George Calfas, who has experience with Edgefield archeological sites as well as the pXRF. Mark is analyzing the empirical data. All of this information will help us start to categorize the face vessels by pottery site, and thus narrow down the date range on each piece. Once the information is analyzed, it will be presented to the exhibition lenders. And hopefully, as more face vessels are analyzed in this way, the database of information can grow.

The face jug analysis was an exciting 2-day process which couldn’t have been possible without each team member’s contribution. We look forward to the results, as well as continuing to put together the puzzle pieces of the face jugs’ story!