Just as there is more to a book than its cover, a new study mapping the elements within an ancient portrait of a Roman woman from Herculaneum demonstrates that there is more to a painting than what may be seen on the surface.
This is a critical discovery as, since the excavation of Herculaneum, one of the Roman towns buried by the volcanic eruption of Mt Vesuvius in 79 AD, much of the uncovered artwork has suffered irreparable damage from exposure to the elements. A better understanding of the chemical make-up of these works will will help improve methods of preservation and restoration.
The portrait of the Roman woman, for instance, was excavated only 70 years ago but thanks to external factors such as humidity, temperature variation and salt it has already lost much of its original magnificence.
In one of the first field studies of its kind, Eleonora Del Federico from the Pratt Institute in the United States and her colleagues used a portable macro X-ray fluorescence instrument, called ELIO, to non-invasively examine this portrait and uncover details of the painting that are no longer visible to the naked eye.
Specifically, this analysis created maps of elements used in the painting such as potassium, iron, copper and lead from which Del Federico and her colleagues were able to glean insights about the process the artist used to create the portrait.
Among other things, they discovered that a green-earth hue containing potassium had been implemented in the underpainting of the cheeks of the woman to give them a flesh-like colour and that the artist initially sketched the image with an iron-based pigment.
Del Federico and her colleagues claim that by using this analysis on more ancient artworks scientists can help conservators choose cleaning solvents that are compatible with the elements in an artwork, which will help to better maintain and restore their original brilliance.
The research will be presented to the 254th National Meeting & Exposition of the American Chemical Society.