Curiosity-driven Research, Curd Rice & Pickle
How a Chennai-trained chemist in Oregon produced the first new inorganic blue in two centuries.
YInMn blue (pronounced “yin-min”) is a vivid, durable blue pigment, and the first new inorganic blue discovered in more than 200 years. Its name comes from its ingredients: yttrium (Y), indium (In) and manganese (Mn), whose oxides are baked together at about 1,200°C to produce a brilliant blue powder. It is non-toxic, does not fade, and reflects solar heat, which makes it promising for outdoor paints, industrial coatings and art. Among admirers in India and elsewhere it goes by another name: “Mas Blue,” after the initials of its inventor, Prof. M.A. Subramanian, a materials scientist from Madras. Mas also means “more” in Spanish, and the name echoes the “MS Blue” of the Carnatic vocalist M.S. Subbulakshmi. The coincidences are pleasing, but the real story is how a colour that humanity chased for millennia turned up when nobody was looking.Why a blue pigment is so hard to make
Modern computers can display a slew of colours, and creative people have always dreamt up unique hues. But to turn any colour, digital or imagined, into something real, like paint for a wall, you need a pigment. Making one takes ingenuity, a very good understanding of chemistry and, yes, some luck. Blue is the hardest case. A material looks blue when it absorbs red and yellow light and lets blue light through or back. Few stable, inexpensive compounds do that cleanly. Many of the ones that do are toxic or unstable. “People have been looking for a good, durable blue pigment for a couple of centuries now,” says Subramanian.A 5,000-year chase
The search is as old as painting. Around 3000 BCE, Egyptians fired sand, copper and a flux to make Egyptian blue, usually considered the first synthetic pigment. The recipe was eventually lost. For centuries afterwards the finest blue came from one place: lapis lazuli, mined in the Hindu Kush mountains of Afghanistan. Carried west across the sea, it earned the name ultramarine, and it cost as much as gold.
Michelangelo knew the pigment was expensive and he wanted to spare no expense for his masterpiece. For The Last Judgement, unveiled in 1541, he insisted on ultramarine for the heavenly skies of the altar wall. When he had painted the Sistine Chapel ceiling, he had accepted a flat rate for labour and paint. This time he billed labour and materials separately. It is human nature to insist on the best materials when someone else, especially someone opulently rich, is footing the bill, and Michelangelo did exactly that. Who can find fault with that?
The first modern synthetic blue, Prussian Blue (also called Berlin Blue), was discovered in the early 18th century, almost by accident, in a failed attempt to make a red dye. It was cheap, and it changed who could paint with blue. Hokusai’s Under the Wave off Kanagawa, first printed around 1830, owes its intense blue to Prussian Blue ink, then a foreign pigment imported from Europe, probably via China.
Cobalt Blue arrived in the early 19th century, and Van Gogh’s Starry Night makes stunning use of it. Synthetic ultramarine followed within a few decades, after a French prize offered for a substitute. We still use a form of it to make white clothes look whiter. Manufactured in bulk, these pigments were just chemicals until artists painted with them.
But none of these was perfect. Prussian Blue can darken and fade under some conditions and reacts badly with alkalis. Cobalt is costly and its mining carries a human and environmental toll. Synthetic ultramarine has none of the charm of the original for artists. For two centuries the palette had no new inorganic blue at all.
The student, the furnace and the shrug
Prof. Subramanian’s route to that gap began on the other side of the world. He earned his PhD from IIT Madras, and recalls writing the first chapter of his doctoral thesis sitting on the grounds of Ashtalakshmi Temple in Besant Nagar, close to the institute’s campus. Nearly all his formal education took place within a few miles of his home in Mambalam, Chennai. After postdoctoral work in Texas, he spent more than two decades as a researcher at DuPont, where he discovered several functional materials, mostly for electronics or energy conversion. He now teaches chemistry at Oregon State University.In 2009, a graduate student in his lab, Andrew Smith, pulverised a mixture of the oxides of yttrium, indium and manganese and baked it, hoping to create a new material for high-tech electronics. The team was exploring manganese oxides for their unusual electrical and magnetic behaviour. When the furnace was opened the next day, a dazzling blue powder was waiting inside.
Subramanian’s first thought, he says, was an uncharitable one: “perhaps, the student has made some mistake.” But he recalled colleagues at DuPont saying that blue pigments are hard to make. Chemists spend careers hoping for such a result. Many would have noticed the colour and moved on. The team repeated the experiment, then tested the material.
