This colorful mystery of Ancient Egypt was just solved in Washington state
The pigment “Egyptian Blue” was invented about 5,000 years ago. It’s the world’s oldest known synthetic pigment. But it was lost to time, until recently.
Scientists at Washington State University not only discovered how to recreate it, they found this ancient blue has hidden potential for modern uses that its inventors may not have realized.
The color varies from a deep blue to a dull grey or dull green, which is often referred to as “Egyptian Green.” Replicas of Egyptian Blue can be found at your local art store, but nobody has made it authentically for at least hundreds of years.
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The distinctive dark blue color comes from the mineral cuprorivaite. The mineral is “excited by red light; it has a luminescence. It gives off infrared light,” John McCloy said.
McCloy is director of the School of Mechanical and Materials Engineering. He co-authored a new study on Egyptian Blue. He explained that the infrared light from Egyptian Blue is invisible to the naked eye.
Researchers found that more materials than just cuprorivaite went into the original color. To find the ancient concoction, WSU teamed up with the Carnegie Museum of Natural history and the Smithsonian Museum Conservation Institute. The results were published in the NPJ Science Journal.
Finding the mysterious recipe
This pigment was often used as a substitute for precious gems throughout history, such as turquoise or lapis lazuli which was imported from places like modern day Afghanistan. It was used to adorn ancient statues, coffins, murals, ceramics, wall paintings, and much more.
There’s also evidence that Egyptian Blue was used in Rome and during the renaissance period. However, the exact recipe was lost to history.
McCloy says it’s unlikely that the ancient Egyptians were aware of the palette's infrared properties, which scientists can detect today. That means Egyptian Blue has potential in modern tech. It could be used for fingerprinting, currency, or passports.
“People have proposed using the material for counterfeit inks,” McCloy said.
Researchers knew a few things about the original blue color. Archeologists have found ancient recipes on how to make it, yet the records aren't exact. While it was known that the cuprorivaite for ancient pigment is made up of calcium, copper, and silica, McCloy said that the sand originally used could have had a lime impurity in it. Recreating this color involved going back in time and experimenting with what ancient craftsmen used. For example, the original pigment likely used natron, which is what was used to mummify pharaohs.
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From there, scientists tried a few different processes. Mixtures were heated to 1,000 degrees Celsius for 1 to 11 hours. Then they tried different cool-down periods. A total of 12 different recipes were ultimately created.
The findings show that the materials that went into Egyptian Blue varied over time and place, which is why there are so many shades of the hue.
Infrared history
The glow from Egyptian Blue's infrared light is bright. Conservators and archeologists have been using the light as a guide to find where the pigment has been used in the past.
“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 said.
Even if there is a coat of white paint on top of Egyptian blue, “You can see the glow coming through. So you can see paintings underneath the paint if you have the blue pigment underneath,” McCloy said.
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McCloy said projects like this don’t come along often. He says he does lots of research that people aren't typically interested in, but research in the realm of Ancient Egypt tends to draw curiosity.
“It hits our humanity or something. In principle you could make these paints in your garage if you had a warm enough furnace. It’s like having a connection with 1,000 year old Egyptians,” McCloy said.
A collection of artifacts that use WSU’s Egyptian Blue recipe are now on display in Pittsburgh’s Carnegie Museum’s “The Stories We Keep Collection: Conserving Objects from Ancient Egypt.”
Those artifacts will be included in the new permanent collection “Egypt on the Nile” that is scheduled to open in 2026.
