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Image: ShutterstockBelieved to be the first artificial pigment produced, Egyptian blue was inspired by the semiprecious stone lapis lazuli.

According to Marc Walton, a research associate professor of materials science and engineering at Northwestern Univ., Ancient Egyptians used the pigment on their walls and on the ceilings of tombs to replicate the night sky. The first documented appearance of the pigment was around 3200 to 3000 BC.

“But then the Romans move(d) away from using blue as a primary color in their painting,” Walton said. “The technology of how to make Egyptian blue dies out in the Dark Ages.”  

Due to its deep, vibrant hue, Egyptian blue was typically thought to be reserved for notable use. However, Walton, along with a team of scientists and art conservators from the university, recently discovered 2nd-century AD artists used Egyptian blue for underdrawings and color modulation.

“The discovery changes our understanding of how this particular pigment was used by artists,” Walton said. “I suspect we will start to find unusual uses for this colorant in a lot of different works of art, such as wall paintings and sculpture.”  

The researchers studied 15 Roman Egyptian portraits and painting fragments, currently housed in the Hearst Museum at the Univ. of California, Berkeley. The artworks were unearthed between December 1899 and April 1900 at the site of ancient Egyptian city Tebtunis, located in the Egypt’s Fayum region.

“With their relatively pristine conservation history and strong contextual information, these portraits are ideally suited to the study of their pigments, layering structure and binding media to establish a more complete understanding of both Roman Egyptian painting practices and the larger social context of their use,” the researchers write. The study recently appeared in Applied Physics A.  

Researchers employed near-infrared (NIR) luminescence imaging to identify the pigments. “The luminescence response of inorganic and organic compounds is recorded in the NIR when excited by visible light. This technique is very sensitive to the detection of Egyptian blue, even in amounts too small to be observed with the naked eye,” the researchers write.

Complementary analysis was achieved through x-ray fluorescence spectrometry, x-ray diffraction and scanning electron microscopy. 

Six of the paintings showed evidence of the pigment.

While the paintings showed no visible or discernable portions of Egyptian blue, it’s hypothesized the pigment’s presence in underdrawings may suggest it was widely available during the time period, making it a feasible alternative for carbon black or chalk.

The passive use may also indicate Roman Egyptian painters didn’t prize blue. Greco-Roman painters relied heavily on yellow, white, black and red, according to the researchers.

According to Walton, Egyptian blue slightly glistens when hit by light. The painters may have been harnessing this trait when using the pigment to modulate their primary colors.

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