This week, the class ventured to The Walters Art Museum where we met with conservation scientist Dr. Glenn Alan Gates and objects conservator Greg Bailey. Through a presentation given by Dr. Gates, our class learned a little more about the history surrounding mummy portraits, some common trends discovered through examining the portraits, and the research on the five portraits in The Walters’ collection. Both The Walters’ team and our class will contribute the research done on these mummy portraits to the APPEAR project, so our meeting was a good way to discuss similarities in our findings and possible areas of study for the future.
Through the presentation, we learned that within the approximately 1,000 known mummy portraits, the portraits are diverse not only in terms of their contemporary context (only about 100 portraits are still attached to a mummy), but also in the material used to construct these works of art (while most portraits are painted on wood, some exist on shrouds). Some paintings, though stylistically similar, have no association with funerary art. In examining what is similar about the two portraits we are researching and the portraits at the Walters, we learned that both groups have portraits with Egyptian blue mixed with lead white in backgrounds that appear gray in normal light. In our own search for Egyptian blue, we had been a bit puzzled that the blue flecks we see in the purple stripes on the tunics that did not luminesce in visible light as expected. Is this evidence of the use of indigo in these areas instead of Egyptian blue? For now it appears this phenomenon will remain a mystery, but Gates suggested, at the very least, we put a camera to the microscope and document it. We also found that madder lake (or possibly kermes) seems to be present on portraits in both collections, and is sometimes used as a highlight under the eyes of the faces. Gates mentioned that that researchers at the UCLA/Getty Conservation Training program have actually developed specific camera filters that allow the possibility of differentiating between a plant based red (madder lake) and an insect red (kermes), which might tell us which material is actually present here.
Again, something that was beneficial about this meeting was what we learned to go back and look for in our own portraits. This list is extensive and includes things found on the Walters’ portraits that, if found in our portraits as well, could indicate a larger trend. Gates suggested we look for small bubbles in our areas with lead white; we had already seen some bubbling in these areas, which Gates surmised could be explained by the fatty acid content in the beeswax reacting with the carbonates in lead white, releasing carbon dioxide and producing lead soaps. Additionally, we hope to take a closer look at the back of our portraits as Gates mentioned that we might be able to see score marks from where the wood was originally cut. On the subject of wood, although our wood has not been analyzed, Gates suspects it is linden wood because of our portrait’s thinness, which characteristically tends to cleave well into thin sheets. After we mentioned that Portrait of a Young Man shows some resin (possibly left behind from the original mummy wrappings) on the back, Gates suggested we look for particles of sand caught in the resin as researchers in Catholic University in Belgium are trying to match the sand granules they found in resin to a specific area in the Fayum. He also reminded us to look for possibly two types of black are used in the portraits (bone black and carbon black)—something that we had already noticed in the hair of our two portraits; according to him, we should go back and look at our XRF analyses and search for evidence of phosphorous especially in the areas associated with bone black.
In expanding on his own research, Gates described his work with x-ray fluorescence analyses of the Walters’ portraits. He found that there appeared to be some specific correlations between chemical elements. One such correlation, was that whenever chromium was present, so too was aluminum, but also iron, sulfur and phosphorous. Further research that involved Transmission Electron Microscopy work at Boise State University with Dr. Darryl Butt showed that a single purple particle extracted from the stripe of one of the paintings might suggest connections how lake pigments (like madder or kermes) were actually manufactured for use on these portraits. All that from a single particle less than a hair’s width in cross-section! We wrapped up our session by looking at two of The Walters’ portraits, the Mummy Portrait of a Woman from Fayum, Egypt and the Mummy Portrait of a Woman. Overall, it was a very exciting and educational week!