How it began
Around 2500 BCE Egyptians became the first culture to develop a synthetic pigment, a blue of various tones. Wikipedia's summary of the literature places its first synthesis in Egypt in the Fourth Dynasty. Egyptians prized blue and wanted to imitate turquoise and lapis lazuli, which were rare and expensive and could only be cut into objects or inlays. No ancient Egyptian text describes how the pigment was made; the first written account is by the Roman author Vitruvius in the 1st century BCE, who called it caeruleum.
How it works
The makers heated a mixture of lime, sand, a copper compound and an alkaline flux. The result was a calcium copper silicate with a stable blue color, whose main coloring agent is cuprorivaite. Modern reconstructions fired the mixtures at about 1,000 degrees Celsius for between one and eleven hours. The ground pigment was mixed with a binder and applied to wood, stone and cartonnage, and it was also used for beads and amulets. Longer heating and slower cooling gave a bluer product, and larger particles gave a deeper blue.
How it spread
Because it cost less than the decorative stones and was easier to apply, Egyptian blue was popular around the Mediterranean for more than 3,000 years, and it was used extensively until the end of the Roman period. Whether its appearance in other regions reflects parallel invention or the spread of the technique from Egypt is unclear.
Who pushed back
Use of the pigment declined after the Roman period, and Wikipedia's account says the method of manufacture was lost in about the 4th century CE. The American Ceramic Society places its final disappearance from use in the Renaissance. Interest returned in the early 19th century, when Humphry Davy investigated it in 1815.
Where it stands today
Egyptian blue absorbs visible light and emits near-infrared light at about 910 nanometers, which lets conservators detect it even when the color has degraded. In 2025 a team led by Washington State University, with the Carnegie Museum of Natural History and the Smithsonian's Museum Conservation Institute, published 12 recreated recipes to understand how ancient makers worked.
