The science of ancient paint
The Fayum portraits owe their startling preservation to two factors: the dry Egyptian climate and the chemistry of their materials. Artists in Roman Egypt created these panels using either tempera (pigment mixed with an animal-glue binder) or, more commonly, encaustic painting. The encaustic method required mixing pigments with hot beeswax, sometimes with oils or resins added to alter the texture and drying time. This wax medium was applied in layers while warm, allowing artists to blend colors and create a depth and translucency that looks like skin tones.
The wooden panels themselves were a valuable commodity. Scientific analysis shows that many portraits were painted on imported wood, with European lime tree (Tilia europaea) being a frequent choice. Other identified woods include oak, sycamore, cedar, and fig. The pigments came from several sources. Iron oxides provided red and yellow ochres, while carbon was used for black. Artists also used a synthetic pigment called Egyptian blue, a type of calcium copper silicate first created thousands of years earlier. Non-invasive imaging techniques, such as visible induced luminescence (VIL), can make this blue pigment glow white in infrared images, revealing its use even when mixed with other colors.
Analyzing the subjects
Modern analytical methods allow scientists to study the portraits without damaging them. Macroscale multimodal chemical imaging, a process that combines X-ray fluorescence and hyperspectral imaging, creates detailed maps of the elements and molecules across a portrait's surface. This reveals the exact composition of the pigments, such as the use of red ochre and lead to create skin tones, or the mineral natrojarosite for a greenish-yellow background. Analysis of a purple pigment used for the clavi—stripes on a toga indicating rank—found it to be a lake pigment derived from plants or insects.
These portraits represent the multicultural elite of Roman Egypt: a blend of Egyptian, Greek, and Roman peoples. While they present as ethnically diverse, dental and skull analyses of the mummies show they were closely related to earlier ancient Egyptian populations. The portraits depict individuals of all ages, from children to the elderly, offering demographic data. The high number of young people in the portraits may reflect the low life expectancy of the period. Paleoneurological studies of the portraits have even identified signs of medical conditions, such as eye disorders like strabismus.