It’s easy to think of blue as a naturally pervasive color. It’s all around us in clear skies and bodies of water. Yet elsewhere blue appears infrequently, coloring only a handful of minerals and less than 10 percent of flowering plants. Even the feathers of birds, from blue jays to bluebirds, are not truly blue but the result of a biologically sophisticated trick of the eye. The scarcity of blue in the natural world has, for much of history, made it hard to reproduce.
“Other colors were made from natural materials that you perhaps processed, but blue as a pigment didn’t already exist and had to be created," says Mark Pollard, professor of archeological science at University of Oxford .
The earliest humans could pick up chunks of red or yellow ochre or white chalk and use them almost like crayons, and black could be found at the end of every burnt stick. But the transformation of natural materials into the color blue, Pollard explains, required considerable effort and ingenuity.
The quest to unlock the secret of that transformation dates back millennia and spans cultures and civilizations, from Bronze Age Central Asia to early imperial China, from medieval Venice to the modern Maghrib (Islamic North Africa).
The breakthrough came more than 5,000 years ago along the banks of the Nile when early Egyptian chemists first brought the color of the sky down to earth.