This week we were visited by Brian Baade, Assistant Professor, and Kristin DeGhetaldi, graduate student, both paintings conservators affiliated with the University of Delaware. With them they brought encaustic paint—pigments mixed with beeswax—and two kinds of tempera paint, one made of animal skin glue and the other of acacia gum. They brought these three different kinds of paints because we cannot be certain about the specific paints used on our mummy portraits without further chemical analysis.
We began class by discussing the different components of paint. To make a paint, you need two things: a pigment and a binder. A binder can be most sticky things, like wax, animal based glues, or plant gums, which have all been identified on Roman Egyptian paintings. Ancient Egyptians obtained their pigments from several sources. Their pigments can be split into two categories—organic and inorganic. Organic pigments are categorized based on the presence of carbon and tend to come from once living sources. Some organic pigments we worked with include bone black (from burnt bones), indigo (from the plant), and rose madder (from the madder root). Inorganic pigments typically come from mineral sources, and some can be toxic. Some inorganic pigments we worked with are red lead, lead white, and Egyptian blue. All of these colors have been found on ancient Roman Egyptian mummy portraits.
After a brief lecture on the basics of painting, we began to work with the paints. We had prepared wooden panels that closely resembled the characteristics of the wood identified on mummy portraits. Instead of European lime wood, we used American basswood, and North Atlantic cedar was used for Lebanese cedar. In antiquity, these woods were prized for their strength and flexibility even when cut very thin, and also produced light boards with minimal cracking and smooth surfaces for painting. Some of our boards were sized with animal glue and the rest were sized with animal glue and gypsum (calcium sulfate mixed with animal glue). We began by sketching drawings on the boards in charcoal, as some evidence from ancient examples suggest. We then began first by painting with pigments mixed with acacia glue, then attempted pigments mixed with animal glue, then pigments in beeswax (or encaustic), and finally beeswax mixed with resin (“Punic wax”).
We observed the differences between the various paints applied to the different woods with different preparation. Overall, it was decided that encaustic paints were the hardest to work with because the pigmented wax, which had to be heated on hot plates to be usable as a paint, cooled remarkably fast. As soon as we would apply even the tempera-based paints, they seemed to dry immediately, leaving us unable to paint anything besides blobs of color. To try to work the paint a bit more and mimic the tool marks found on our portraits, we heated metal tools and pressed them into the painted wax, simultaneously melting and shaping the paint. While this worked for very small areas of paint, we had to keep a constant heat source on the tool in order for it to function over large portions of painted surface. Towards the end of class, we experimented with the process of gilding. This procedure was also extremely difficult. The thin pieces of gold would flutter away at the slightest hint of a breath; in order for them to stick to our painted wood, we had to paint additional glue on our panels, or heat the encaustic slightly to get the gold to adhere.
As a class, we had a newfound appreciation for the artists of our portraits because all of the possible paints they had to work with were incredibly difficult to manipulate. We hope this will elucidate the medium and painting techniques of our mummy portraits.