While most of us don’t think much about the man-made colors that surround us, for researchers and manufacturers, pigments are important for both their beneficial and harmful effects. For example, 33 percent of one popular pigment, cobalt blue, is carcinogenic, which has led researchers to find a new alternative.
While we might take the colors we see on packages, billboards, in clothing, and in print for granted, there was a time when pigments were tantamount to treasure. A pound of purple wool, for example, used to cost more than a year’s salary for most people because it would take the secretions from 250,000 sea snails to make an ounce, according to the History Channel. And red pigments from the cochineal beetle, as discovered from the Aztecs by Spanish raiders, became one of the most lucrative trades in 1570s Europe, according to the BBC.
Of course, pigments had their dark side too. It’s widely believed that Napoleon was killed as the green pigment in the wallpaper of his prison cell released arsenic. And before World War II, manufacturers were using a pigment called uranium oxide in dishware, which was obviously a bad idea due to the radioactivity the color emitted. Most people are also now familiar with the dangers of lead, which was a staple in white paint for decades.
A Better Blue
Blue is also not without its problems. Just like other pigments, it has a rich history, including the fact that the lapis lazuli used by the Babylonians and Egyptians about 6000 years ago was more valuable than gold. But just like the dangers posed by the pigments of the past, today’s cobalt blue—which has been in use for over 200 years—consists of more than one-third cobalt ions that are carcinogenic.
So researchers at Oregon State University set out to find a better blue. They turned to a mineral called hibonite, which is named after French prospector Paul Hibon, who discovered the mineral in Madagascar in June 1953. Hibonite can take on many shades, including a light blue hue, which drew the researchers’ attention.
After working some chemical magic on the mineral, the scientists derived a series of blue pigments that have several distinct advantages over cobalt blue. For one, they are just as vivid yet more stable and can even stand up to acidic and basic solutions. Secondly, they only consist of four percent cobalt ions versus 33 percent, so they are significantly safer to produce and use. And finally, the hibonite blues reflect near-infrared light, which, the researchers say, could make them useful in heat-reflective coatings.
The work has been published in the journal ACS Omega.