A tiny speck of purple paint from the 2nd century AD may yield clues to how ancient artists created the extraordinary portrait panels that accompanied mummified bodies into the afterlife.
Known as โFayum portraitsโ, after the area in Middle Egypt where they were found, these vivid likenesses date from the Roman occupation of Egypt between 30 BC and the middle of the 3rd century AD. Painted on wood panels or linen, the portraits were attached to the bound bodies of their subjects. Today, more than 1,000 of these mummy portraits survive in museums and collections around the world. They depict a range of men and women, from the very young to the very old โ but little is known of the artists who created them, or where and how they were made.
One such Fayum portrait, known as the โPortrait of a Bearded Manโ (c.AD 170-180), was acquired by the Walters Art Museum in Baltimore, Maryland, in 1912. It portrays a man wearing a toga bearing two clavi (purple stripes used to denote high status, worn by, among others, Roman senators). Under examination at the museum, it was noticed that the particles used to paint the clavi appeared different in structure from other paint particles on the thin wooden panel. Might a โspecialโ paint have been used to further enhance the idea of high status? In order to find out, a 50-micron sample of the pigment was sent to Darryl Butt, a materials scientist at the University of Utah, for further analysis.
The use of the colour purple to denote high status was common. The most-valued ancient colour was Tyrian purple, an organic substance extracted from the glands of sea snails and used as a simple dye or colouring agent. In the case of the clavi, the purple used seemed to have a gem-like structure, and under UV radiation appeared not as a simple dye. Analysis showed that the paint was in fact a pigment that contained a combination of different components, including lead and chromium.
One possible explanation, Butt suggests, is that the elements could have been picked up incidentally as part of the production process of dyeing. As only a small amount of lead was found to be present, it might be that its inclusion was not intentional but was instead a result of using a lead-lined dyeing vat.
โOver time, a story or hypothesis emergedโ, Butt says, โsuggesting that the Egyptian dyers produced red dye in these lead vats.โ And when they were done dyeing at the end of the day, he adds, there may have been a sludge that developed inside the vat that was purplish in colour. โOr they were very smart, and they may have found a way to take their red dye, and to shift the colour towards purple by adding a salt with transition metals and a mordant [a substance that fixes a dye] intentionally to synthesise a purple pigment.โ At the moment, Butt admits, we simply โdonโt knowโ.
Another portrait found to contain the same element, chromium, in its purple pigment is the โPortrait of a Young Girlโ in the collection of the Museum of Fine Arts, Houston. Other similarities, such as the shape of its wooden panel and the background colour used, and even stylistic connections, could mean that the panels were produced in similar places or times, and in some cases, even by the same artist.
As most mummy portraits were grave-robbed, a lack of archaeological context means that studies like this, published in the International Journal of Ceramic Engineering and Science, can provide valuable information. In an international collaboration entitled APPEAR (Ancient Portrait Paintings: Examination, Analysis, and Research; http://www.getty.edu/museum/research/appear_project), 47 museums with mummy portraits are collating such findings to learn more about the makers of these extraordinary portraits and their methods.
Images: Museum of Fine Arts, Houston, Estate of Isabel B Wilson.
