Mummy art: Micro-Raman finds artist

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  • Published: Mar 1, 2016
  • Author: David Bradley
  • Channels: Raman
thumbnail image: Mummy art: Micro-Raman finds artist

Telling clues

Credit: Phoebe A. Hearst Museum of Anthropology, University of California, Berkeley Roman-era Egyptian mummy portraits from the site of Tebtunis, Egypt. Northwestern researchers discovered all three share similar style, materials and layering structure of paint, leading them to conclude the three paintings were made by a single artistic hand. From the left: “Portrait of a Boy,” “Portrait of a Young Man” and “Portrait of a Bearded Man.”

Scientists in the USA have used micro-Raman spectroscopy and other techniques to take a close look at three life-like portraits of mummy faces from 2000 years ago that suggest they are by the same Romano-Egyptian artist.

Marc Walton and his interdisciplinary team at Northwestern University have uncovered telling clues about the underlying surface shapes and colours of ancient paintings that offer strong evidence as to how many of the 15 known mummy portraits and panel paintings were made. Walton, is a senior scientist at the University's Art Institute of Chicago Center for Scientific Studies in the Arts (NU-ACCESS) and reported details of the two-year study at this year's meeting of the American Association for the Advancement of Science (AAAS) in Washington DC.

Critical understanding

Critical to understanding artwork is the identification of the specific pigments and paints used by the artist. The researchers have identified these and can describe the order in which the paints were applied and to which regions of the artwork and with what style of brush stroke; they can even reveal the sources of pigments used. Fundamentally, the detailed analysis of the pigments and their distribution reveals that three of the mummy paintings were painted in the same workshop and were most likely painted by the same artist. This knowledge will help scientists, art conservators and art historians better understand how painting techniques evolved in the Byzantine Empire and subsequently.

"Our materials analysis provides a fresh and rich archaeological context for the Tebtunis portraits, reflecting the international perspective of these ancient Egyptians," explains Walton. "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’s presentation to the AAAS entitled "Romano-Egyptian Mummy Portraits from Tebtunis, Egypt," was part of the symposium "Faked or Changed? Using Science to Reconstruct Object Biography." Intriguingly, 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 a century ago at the site of Tebtunis, modern-day Umm el-Breigat, in the Fayum region of Egypt. All of the paintings are housed at the Phoebe A. Hearst Museum of Anthropology at the University of California, Berkeley.

Colourful data

"Our goal is to use objects themselves as evidence for their production,” Walton adds. "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." Walton's team worked with the museum's art conservators to use non-destructive and non-invasive techniques to get as much information as possible from the paintings without damaging them in any way. Key analytical tools were developed by optics expert and team member Oliver Cossairt and signal processing analyst Aggelos Katssagelos of the McCormick School of Engineering and Applied Science. Cossairt's computational cameras captured 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.

The team also collected data across the ultraviolet to near-infrared range to obtain additional details. Regions were compared to database entries for reflectance spectra of pigments used in the Roman period and mined using Katasaggelos’ machine-learning algorithms. The team could then use this information as a guide to take microscopic samples from discrete areas of the paintings to carry out Raman microspectroscopy and scanning electron microscopy and so obtain characteristic fingerprints for the pigments.

Related Links

AAAS 2016, online: "Romano-Egyptian Mummy Portraits from Tebtunis, Egypt"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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