In ancient Egypt the sky was a gleaming blue, the sacred lotuses had blue petals, the pharaoh’s battle crown was blue, beautiful women wore chokers made of blue stone, and, above all, the life-giving Nile was blue. The ancient Egyptians needed azure pigment to portray these essential elements of life within their sacred art, but the only natural blue pigments were from turquoise and lapis lazuli—semi-precious stones which were rare and expensive. To provide a sufficient supply of blue pigment for painting, jewelry, and sculpture, the Egyptians therefore invented the first synthetic pigment which today is appropriately known as “Egyptian blue” (well, it is also appropriately known as calcium copper silicate–CaCuSi4O10 or CaO·CuO·4SiO2—but I’m going to keep calling it Egyptian blue).
Egyptian blue was synthesized in the 4th Dynasty (c.2575-2467 BC) when the newly created pigment was first used to color limestone sculptures, beads, and cylinder seals. Its use became more prevalent in the Middle Kingdom, and then increased again during the New Kingdom when blue was used for the production of numerous everyday objects. Throughout the Hellenic and Roman age, Egyptian blue was a mainstay of the nascent chemical industry, and it found its way into all sorts of art, jewelry, crafts, and artisan wares. Then, in the fourth century the secret of its manufacture was lost. Only in the beginning of the nineteenth century did interest revive as the English and French pioneers of the chemical trade rushed to synthesize useful compounds. As one might surmise from the fact that the manufacturing process was lost for a millennium and a half, the method to make Egyptian blue is surprisingly involved. Citing a British Museum publication, Wikipedia describes it thus:
Several experiments have been carried out by scientists and archaeologists interested in analyzing the composition of Egyptian blue and the techniques used to manufacture it. It is now generally regarded as a multi-phase material that was produced by heating together quartz sand, a copper compound, calcium carbonate, and a small amount of an alkali (plantash or natron) at temperatures ranging between 800–1000 °C (depending on the amount of alkali used) for several hours. The result is cuprorivaite or Egyptian blue, carbon dioxide and water vapor…
The Egyptians were clearly people who took their pigments seriously, and thankfully so–the blue tints they crafted have lasted for thousands of years (and helped us find our way to synthesized pigments). It is strange to think of the subtle ways that the Nile still flows through our lives.