This week, we had the opportunity to speak with Jane Williams, Head of Collections and Conservation at the Phoebe A. Hearst Museum of Anthropology at the University of California, Berkeley. The portraits she discussed were excavated in 1899 by papyrologists Bernard P. Grenfell and Arthur S. Hunt working just outside of the site of Tebtunis in the Fayum. They collected nearly 30,000 papyrus fragments, most of which were found inside the over 1000 crocodile mummies found at the site. In addition to papyri, over 1800 objects were found during excavation, including their collection of Roman Egyptian portraits which are unique in having come directly from the site of excavation to the museum and having never been on the art market. Thus their surfaces, while not necessarily the most pristine, are remarkably free of post-manufacture restorations. Most well published of the portraits is the portrait sketch of a woman which features notes describing how the image should look, what jewelry and colors should be included, and even a comment about how “the eyes should be made softer”.
While all of the Tebtunis portraits were found at that site, they show variations in manufacturing and production. Williams described how the portraits at the Hearst were placed into groups for study: the “pink ladies,” who were named for their pink garments, and a group of male portraits. The aim of their current research was to use entirely non-destructive techniques to study the portraits for inclusion in the APPEAR database. The first surprise was the background of the paintings. They were able to find the pigment Egyptian Blue on the portraits of the men through visible induced infrared luminescence imaging, which was confirmed through X-ray fluorescence (XRF) in which they found the element copper in the background. However, the female portraits did not show any Egyptian blue. The “pink ladies” were confirmed as having been painted in encaustic using Fourier Transform Infrared Spectroscopy despite the fact that the paint layer was extremely damaged and thin with very little binder remaining. Limewood was used on the female portraits and one of the male portraits they have studied (as were the paintings of our two men at the Archaeological Museum), while three of the male portraits were completed on thicker oak panels. Even the thickest limewood panels are deformed or bent, where they were placed over the face of the mummy, while the oak panels are much flatter, but prone to splitting.
By including a calibration target in Photometric Stereo (similar to Reflectance Transformation Imaging), researchers from the Northwestern University/Art Institute of Chicago Center for Scientific Studies in the Arts (NU-Access) were able to measure the surface texture data to get a sense of what kinds of brushes might have been used. In one area on the background of a male portrait, they consistently got a measurement of about fifty microns for an individual brush hair; this strand diameter is approximately that of a squirrel. It would be interesting to see if our portraits have brush strokes of a similar size! They also found bubbling in areas painted with lead white which they think are a result of the formation of lead soaps. We also found bubbling (with a textile impression) on the proper right cheek of the young man. This bubbling could also be due, in part, to lead soaps.
We also compared some of our data with the information gathered thus far at the Hearst. Williams noted that they have found white chalky underdrawings—possibly gypsum (calcium sulfate)—on all their portraits, and has been wondering whether this was a local Tebtunis practice. When using XRF, they found the presence of sulfur not only in these areas but all over the portraits. We also have noted the presence of sulfur (and calcium) on our portraits, but had not seen any chalk underdrawings or any gypsum preparatory layer. So what could this sulfur be from? We also discussed the presence of tin in our XRF spectra in areas of jewelry—which is also something that has been noticed on one portrait at the Hearst. What could this be related to?
After Williams spoke with us, we completed some XRF work with the “Portrait of a Man”, which yielded similar results to “Portrait of a Young Man”. As this project comes to a close, it’s important for us to be able to bring all of the information that we’ve collected together. Speaking to Williams gave us an opportunity to compare the data that we’ve collected to another set of information about the Fayum mummy portraits.