Mummy portraits hold ancient clues

Washington: Scientists have uncovered telling clues about the underlying surface shapes and colours used by Roman-Egyptian artists to paint lifelike mummy portraits more than 2,000 years ago.

The new details uncovered by using sophisticated scientific tools provide the researchers with very strong evidence as to how many of the 15 mummy portraits and panel paintings were made.

These visages of the dead are considered to be antecedents of Western portraiture, according to researchers from Northwestern University in US.

They identified pigments used by the artists and the order the paints were applied and to which regions, as well as sources of materials and the style of brushstrokes used.

Details of the pigments and their distribution led the researchers to conclude that three of the paintings likely came from the same workshop and may have been painted by the same hand.

This knowledge will help better understand how painting techniques evolved in the Byzantine Empire and beyond.

"Our materials analysis provides a fresh and rich archaeological context for the Tebtunis portraits, reflecting the international perspective of these ancient Egyptians," said Marc Walton from Northwestern University.

"For example, we found that the iron-earth pigments most likely came from Keos in Greece, the red lead from Spain and the wood substrate on which the portraits are painted came from central Europe. We also know the painters used Egyptian blue in an unusual way to broaden their spectrum of hues," Walton said.

The well-preserved mummy portraits are extremely lifelike paintings of specific deceased individuals. Each portrait would have been incorporated into the mummy wrappings and placed directly over the person's face.

They were excavated more than 100 years ago at the site of Tebtunis (now Umm el-Breigat) in the Fayum region of Egypt. Researchers used non-destructive and non-invasive techniques to extract information about the paintings' underlying surface shapes and colour.

"Our goal is to use objects themselves as evidence for their production. In our interrogation, we have used a number of cutting-edge analytical tools developed here at Northwestern to uncover new and intriguing clues about how to identify the hand of an individual artist," said Walton.

Researchers used computational cameras to capture a series of images of the portraits under different angles of illumination to examine the surface shape of the objects.

Using an imaging algorithm called photometric stereo, the researchers were able to recover quantitative measurements of brush and tool marks.

The method also was used to determine how the artist layered the paint and to establish the order of the various pigments used in the paintings.