How much information can you get from a stain of purple pigment, not larger than the diameter of a hair, picked from an Egyptian portrait that is almost 2,000 years old? Lots, according to a new study. Analysis of that stain can teach us about how the pigment was made, what it is made of – and maybe even a little about the people who made it. The study is published in International Journal of Ceramic Engineering and Science.
“We are very interested in understanding the meaning and origins of the portraits and finding ways to connect them with and come up with a cultural understanding of why they were painted in the first place,” says materials researcher Darryl Butt, co-author of the study and dean of the College of Mines and Earth Sciences.
The portrait, which contained the purple pigment, came from an Egyptian mummy, but it does not look like what one might originally think of as a mummy – not like the golden sarcophagus of the Tutankhamen or the side-facing paintings on murals and papyri. Not like Boris Karloff, either.
The portrait, called “Portrait of a Bearded Man”, dates from the second century when Egypt was a Roman province, and therefore the portraits are more lifelike and less hieroglyphic than Egyptian art from earlier eras. Most of these portraits come from a region called Faiyum, and it is known to exist around 1,100. They are painted on wood and were wrapped in the bedding that held the mummified body. The portraits were intended to express the person’s similarity, but also their status – either actual or ambitious.
This idea of status is actually very important in this case because the man in the portrait we focus on wears purple marks called Vinegar on his gown. “When the purple pigment appeared in pianothe purple mark on the gown that in ancient Rome indicated senatorial or equestrian rankings – it was thought that we might see an enhancement of sitters’ significance in the afterlife, “says Glenn Gates of the Walter’s Art Museum in Baltimore, where the portrait is located.
The color purple, Butt says, is considered a symbol of death in some cultures and a symbol of life in others. It was associated with royalty in ancient times and still is today. Paraphrasing author Victoria Finlay, Butt says that purple, located at the end of the visible color spectrum, may indicate the end of the known and the beginning of the unknown.
“So the presence of purple on this particular portrait made us wonder what it was made of and what it meant,” Butt says. “The color purple stimulates many questions.”
Through a microscope, Gates saw that the pigment resembled crushed gemstones containing particles ten to a hundred times larger than typical paint particles. To answer the question of how it was made, Gates sent a particle of the pigment to Butt and his team for analysis. The particle was only 50 microns in diameter, about the same as a human hair, which made it possible to keep track of the challenging.
“The particle was sent to me from Baltimore, sandwiched between two glass sliders,” Butt says, “and because it had moved about a millimeter in transit, it took us two days to find it.” To move the particle to a sample holder, the team used an eyelash with a small amount of adhesive at the tip to make the transfer. “The process of analyzing something like this is a bit like having surgery on a flea.”
With the particle as small as it was, the researchers were able to process even smaller samples using a focused ion beam and analyze these samples for their basic composition.
What did they find? To put the results in context, you need to know how dyes and pigments are made.
Pigments and dyes are not the same thing. Dyes are the pure dyes, and pigments are a combination of dyes, minerals, binders, and other components that make up what we might recognize as paint.
Originally, purple dyes came from a gland of a genus called sea snails Murex. Butt and his colleagues assume that the purple used in this mummy painting is something else – a synthetic purple.
The researchers also assume that the synthetic purple could have originally been discovered by accident when red dye and blue indigo dye are mixed together. The final color may also be due to the introduction of chromium into the mixture.
Thereafter, the mineralogy of the pigment samples suggests that the dye was mixed with clay or a silica material to form a pigment. According to Butt, a skilled painter himself, pigments produced in this way are called sea pigments (derived from the same root word as varnish). In addition, the pigment was mixed with a beeswax binder before it was finally painted on linden wood.
The pigment showed signs of a crystal structure in the pigment. “Sea pigments were considered to be without crystallinity prior to this work,” says Gates. “We now know that crystalline domains exist in lake pigments, and these can act to ‘capture’ evidence of the environment during pigmentation.”
The bottom of the barrel, is, cotton wool
Another detail added a little more depth to the story of how this portrait was made. The researchers also found significant amounts of lead in the pigment, linking that finding to observations from a late British explorer from the late 1800s who reported that dyes in Egyptian dye workshops were made of lead.
“Over time, a story or hypothesis emerged,” Butt says, “suggesting that the Egyptian dyes produced red dye in these lead vessels.” And when they finished coloring at the end of the day, he says, there may have been a sludge that developed inside the tub that had a purple color. “Or they were very clever, and they may have found a way to take their red dye, change the color to purple by adding a salt with transition metals and a mordant [a substance that fixes a dye] to consciously synthesize a purple pigment. We do not know. “
This is not Butt’s first time using scientific methods to learn about ancient works of art. He has been involved in previous similar studies and has drawn on both his research and artistic background to develop a class called “The Science of Art” that included studies and discussions on topics involving dating, understanding and reverse engineering of a variety of historical artifacts ranging from groundbreaking newspapers to ancient art.
“Mixing science and art together is just fun,” he says. “It’s a great way to make learning science more accessible.”
And the work also has broader impacts. Relatively little is known about the mummy portraits, including whether the same artist painted several portraits. Analysis of pigments at the atomic level can provide the chemical fingerprint needed to connect portraits to each other.
“Our results suggest a tool for documenting similarities in terms of time and place of production of mummy portraits, as most were excavated and lack archaeological context,” says Gates.
“So we can possibly connect families,” Butt adds. “We can possibly connect artists to each other.”
Professor works to help solve the mystery surrounding the portrait of a mummy
Glenn Gates et al., Microstructural and chemical characterization of a purple pigment from a Faiyum mummy portrait, International Journal of Ceramic Engineering & Science (2020). DOI: 10.1002 / ces2.10075
Provided by the University of Utah
Citation: Science Reveals Secrets from a Mummy’s Portrait (2020, November 20) Retrieved November 20, 2020 from https://phys.org/news/2020-11-science-reveals-secrets-mummy-portrait.html
This document is subject to copyright. Except for fair trade for private examination or research, no parts may be reproduced without written permission. The content is provided for informational purposes only.