Deep beneath the heart of Rome, underneath Nero’s lavish Domus Aurea, archaeologists have uncovered a rare ingot of Egyptian blue — the world’s first synthetic pigment. Hidden for nearly 2,000 years, this vivid blue treasure sheds new light on artistry of ancient master painters. It also connects Rome’s vibrant history to both Ancient Egypt and the Renaissance, where masters like Raphael revived its brilliance.

A tyrant with a taste for fine art

It’s rare to find a more infamous ruler than Nero. He became an Emperor in the year 37 at the age of just 16, and quickly became notorious for his cruelty and debauchery. He allegedly murdered his mother and didn’t do much for the needs of the Empire and its people. Instead, his reign was marked by lavish spending on art and architecture, most notably the Domus Aurea, his grand palace. Nero was also accused of starting the Great Fire of Rome in the year 64. Although this is likely false, he did redirect resources to rebuild the city to his liking.

Ultimately, Nero’s erratic and suppresive rule led to widespread unrest. He was declared a public enemy by the Roman Senate and committed suicide, marking the end of his dynasty.

Now, archaeologists exploring the Domus Aurea have found several artifacts, including a chunk of one of the most famous pigments in history: Egyptian blue.

A blue unlike any other

Blue is not an easy color to produce artificially. In ancient times, you needed specific minerals like malachite or azurite to create the blue pigment. Egyptians would heat a mixture of sand, ground limestone, and one of these minerals at high temperature. This process would create a blue glass-like structure that was then crushed and combined with a thickening agent to create a durable and intense pigment. It’s the oldest synthetic pigment we know of and for the ancient Romans, it must have cost a fortune.

Remnants of Egypian blue had been found in Pompeii, in areas of wealth and luxury. The discovery of such a significant quantity of Egyptian blue in the imperial palace underscores the sophistication and expertise of the artists who decorated Nero’s residence, using rare and expensive pigments.

The size of the ingot found in Nero’s palace is very unusual. Archaeologists typically discover Egyptian blue in the form of powder or tiny fragments, whereas this specimen is a whopping 2.4 kilograms (5.29 pounds). The intensity of the color is also striking.

“The charm transmitted from the depth of blue of this pigment is incredible,” comments Alfonsina Russo, Director of the Archaeological Park of the Colosseum, who investigated the area. “The Domus Aurea once again excites and returns the brilliance of the colours used by the painters who skillfully decorated the rooms of this precious and sophisticated imperial palace”.

The pigment was lost for centuries — or so we thought

Egyptian blue was used for thousands of years, but researchers thought it was lost for centuries and only rediscovered by the British chemist Humphry Davy in the 1800s. There are no written mentions in Egyptian texts on how to manufacture it. In fact, the production method is only mentioned in Roman literature in the first century BC.

This pigment was used in almost exclusivity to create blue in ancient times. Its use declined and disappeared throughout the Middle Ages. Remarkably, however, the Renaissance painter Raphael used Egyptian blue in one of his most famous paintings, the Triumph of Galatea. It’s unclear if the recipe was lost and Raphael recreated it or it simply fell out of favor for some reason.

The ongoing study of this sector of the Domus Aurea may provide new history for the pigment’s use during the Renaissance, as seen in Raphael’s Triumph of Galatea. The brilliance of Egyptian blue connects the painters of antiquity with those who rediscovered its magic centuries later.