Archaeologists Are Recreating the Long-Lost Recipe for Egyptian Blue, the World’s Oldest Known Synthetic Pigment
Created 5,000 years ago, the mysterious color has been found on artworks and artifacts throughout the ancient world. But the pigment’s recipe was eventually lost to history
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Thousands of years ago, the Egyptians created the world’s oldest known synthetic pigment: Egyptian blue. Despite its name, the mysterious material’s true color ranged from blue to green. Archaeologists have spotted it on ancient coffins, sculptures, murals and ceramics.
The oldest known sample of Egyptian blue decorates a small alabaster bowl dating to 3250 B.C.E. The pigment was later used by the Romans, who conquered ancient Egypt in the first century B.C.E., and then by Renaissance artists.
The color eventually faded into obscurity. But now, scientists have finally figured out how to bring it back to life.
Researchers from Washington State University, the Carnegie Museum of Natural History and the Smithsonian’s Museum Conservation Institute recently teamed up to recreate Egyptian blue. According to a study published in the journal NPJ Heritage Science, the team created 12 different recipes for the pigment, combining crystalline silicon dioxide, copper, calcium and sodium carbonate. They then heated these mixtures at more than 1800 degrees Fahrenheit for up to 11 hours.
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“One of the things that we saw was that with just small differences in the process, you got very different results,” lead author John McCloy, director of Washington State’s School of Mechanical and Materials Engineering, says in a statement.
The 12 pigments are united by one key quality: They contain a mineral called cuprorivaite, which is “excited by red light,” McCloy tells Natalie Akane Newcomb of KUOW, Seattle’s NPR member station. “It has a luminescence. It gives off infrared light.”
Archaeologists have long known about this quality, and they’ve used red light to identify Egyptian blue on artifacts before. This technique will expose the pigment even through other layers of paint.
“You could have a painting that was repaired later with a different blue, and you can very clearly see where the Egyptian blue is by shining a light on it and then looking at it in the infrared,” McCloy tells KUOW.
Five years ago, researchers discovered that Raphael used Egyptian blue in a fresco called Triumph of Galatea, which the Renaissance painter created for Rome’s Villa Farnesina in around 1512. Raphael may have recreated the old pigment to mimic a technique used by the ancient Romans, who commonly mixed a bit of Egyptian blue with white to make human eyes “seem translucent and more natural,” as Chemistry World’s Tom Metcalfe reported in 2020.
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“Many paintings have this pigment,” McCloy tells Chemistry World. “It can be used to luminesce through other layers of paint, so that you don’t see any blue on the surface.”
Since Egyptian blue emits light that can’t be seen with the naked eye, some experts have proposed novel use cases. For instance, it could be repurposed for fingerprinting or as counterfeit-proof ink.
“It’s this coming together of art and science to be able to find solutions for the future from information from the ancient past,” Simon Lewis, a chemist at Curtin University in Australia, told the Australian Broadcasting Corporation’s Nicolas Perpitch in 2016.
Though cuprorivaite was the main ingredient used in Egyptian blue, the pigment’s final hue was determined by its additional components. In the recent study, researchers experimented to see how different ingredients would affect the color. They then used microscopes to study their results and compare them to pigments found on two ancient Egyptian artifacts.
“The production of Egyptian blue was a highly sophisticated process, made possible only within a well developed cultural and technological context,” Moujin Matin, an archaeologist at the University of Western Ontario who wasn’t involved in the research, tells Chemistry World. “Culturally, the prominence of blue in religious symbolism and daily life gave the pigment special significance, ensuring its sustained value and use.”
