4 min. read
Egyptian blue, considered the world’s earliest synthetic pigment, was prized for its stable, blue hues and served as a common blue paint in Egypt as early as 5,000 years ago, as well as the base material for small items such as beads and vessels in later periods.
But it was also used in northwestern Iran nearly 2,000 years later. Almost 500 artifacts made from molded Egyptian blue paste were discovered in the Iron Age II period at Hasanlu during the Hasanlu Project and at nearby Dinkha Tepe during Penn Museum-led archaeological expeditions that ran in the 1950s to 1970s.
Penn Today spoke with archaeometallurgist Vanessa Workman of the School of Arts & Sciences and museum conservator Alexis North of the Penn Museum about Egyptian blue and their collaborative approach to investigating its cultural and economic significance in the ancient world.
Egyptian blue is a synthetic pigment that gets its color from crystals and has the same chemical composition as the naturally occurring mineral cuprorivaite, says Workman, who also has an appointment at the Penn Museum in the Center for the Analysis of Archaeological Materials.
“Cuprorivaite is found very, very rarely in Earth’s geology, and so the occurrence of it is mostly synthetic—human-produced,” she says. “It’s a unique situation where humans were using a complex technological process to produce a color.”
And it is the earliest known synthesized pigment in the world. “People were taking minerals like yellow ochre that they found around them and putting it into a fire to turn it red hundreds of thousands of years ago,” she says. “But this is the first example of ancient craftspeople using pyrotechnology to drastically change the composition of a mixture of materials to create color.”
To make Egyptian blue, says Workman, artisans mixed together a copper-containing material, silica (usually quartz sand), an alkali (most commonly plant ash or natron), and calcium carbonate (such as limestone); ground it into a fine powder; and then fired it to a specific temperature in a closed container.
“This process can form a green color as well—a pigment called Egyptian green,” says North. “It’s chemically very similar, but has a slightly different crystal structure. So, they figured out how to adjust the recipe to ensure that it was the hue they wanted.”
The next synthesized pigment, Han blue, which has a similar production process to Egyptian blue, wasn’t developed until much later—more than 2,000 years, she adds. And then there is Maya blue, made by chemically bonding a type of clay with indigo, more than 1,000 years after that.
“The color blue is not common in the mineral world,” says Workman, adding that producing blue required more effort than the other colors they were using. “Creating this blue pigment was clearly thought out—deliberate,” she says. “It is an example of ‘We want this. How can we make it?’”
Egyptian blue was primarily used as a pigment, says North, adding that most of the blue paint in Egyptian art is Egyptian blue. But it was also molded into small objects such as beads and amulets.
The identification of Egyptian blue has been aided by its distinct luminescent properties, she adds, which can be detected with infrared photography.
“It has become standard practice for us [in museum conservation] to photograph anything we think might have a trace of Egyptian blue,” says North. “It is easy to do and noninvasive.”
In fact, Workman adds, it was a student project that helped focus their attention on the Egyptian blue at Hasanlu.
“We realized how much material was there and how exceptional it was,” she says. “It was being used on a totally different scale—in ancient Egypt and the Near East, people painted things and made small beads and scarabs with the pigment, and then suddenly we have these large furniture legs, vessels, decorative wall tiles, bracelets, and anklets.”
Now that the Egyptian blue objects from the sites are catalogued, they are working to analyze the pigment itself—testing for chemical variations, understanding production techniques with microscopy, and determining effects caused by the catastrophic destruction of Hasanlu during the Iron Age. They are also analyzing isotopic signatures of the raw materials, which can help trace their sources and narrow the area of production.
These findings, says Workman, will help them better understand the history of Hasanlu.
“If the pigment was made in northwestern Iran, then this is the earliest example of its production outside of Egypt,” she says. But questions remain regarding how these artisans got the materials needed for Egyptian blue and where they learned the techniques to make it.
Analyzing the chemical and isotopic signatures of an object are tools to help look at human movement and connections as well as the history and pathways of technology, says Workman.
“We’re constantly discovering that humans moved in much vaster areas than we thought they did in the past,” she says. “So having these analytical tools to understand the movement and interactions of cultures in a deeper way is very valuable.”
North agrees: “At the core of what we do—what these collections are here for—is to learn about people.”
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