Making colour
The blue problem: Egyptian blue to YInMn blue
Good blue pigment is rare in nature, so people have invented it again and again, from ancient Egypt to an Oregon lab in 2009.
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Blue is the hardest colour to find in the ground. There are few blue minerals, and the best, lapis lazuli, was scarce and costly. So blue has a history of invention. Egyptians made the first known synthetic pigment about five thousand years ago. Later came Prussian blue, cobalt blue and synthetic ultramarine. The newest, YInMn blue, was found by accident in 2009.
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Ancient blues
Egyptian blue is made by heating sand, a copper mineral, lime and an alkali to around 900 degrees Celsius. It is a calcium copper silicate, and it colours tomb paintings, statues and glazed objects. Its recipe was lost after Roman times. Chinese makers separately invented related barium copper silicates, now called Han blue and Han purple, seen on the Terracotta Army. The Maya made a turquoise blue by heating indigo with a white clay called palygorskite, which locks the dye in so firmly that murals more than a thousand years old are still bright.
The search in Europe
European painters depended on azurite and on ultramarine from Afghan lapis lazuli, which was costly enough to be written into contracts. Around 1706 a Berlin colour maker produced a deep blue by accident, from iron salts and an alkali contaminated with animal matter. Prussian blue was cheap and strong. It later gave the Japanese printmaker Hokusai the blues of the Great Wave, and gave architects the blueprint. Cobalt blue followed in France in 1802. In the 1820s a French prize was won for synthetic ultramarine, chemically the same as the lapis pigment and a small fraction of its price.
YInMn blue
In 2009, in the laboratory of Mas Subramanian at Oregon State University, a graduate student heated a mixture of yttrium, indium and manganese oxides in a furnace while looking for materials for electronics. One sample came out a vivid blue. Named YInMn blue after its three elements, it is stable, does not fade and reflects heat, which makes it useful for cool roof coatings. It was approved for industrial use in the United States in 2017 and for artists' paints in 2020. It remains expensive because indium is scarce.
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Sources and further reading
- YInMn Blue on Wikipedia
- ColourLex: Egyptian blue
- Oregon State University, Department of Chemistry: The Story of YInMn Blue
- The Conversation: From the Great Wave to Starry Night, how a blue pigment changed the world
- Al Jazeera: Maya blue, the mystery dye recreated two centuries after it was lost
Original text by the Rang desk, written with AI assistance and checked against the sources above. Meanings of colour vary from place to place and person to person. If we have something wrong, tell us.