World's Whitest Paint Is Now Thin Enough to Coat Cars, Spacecraft
Monisha RavisettiFormer Science Writer
Monisha Ravisetti was a science writer at CNET. She covered climate change, space rockets, mathematical puzzles, dinosaur bones, black holes, supernovas, and sometimes, the drama of philosophical thought experiments.
Previously, she was a science reporter with a startup publication called The Academic Times, and before that, was an immunology researcher at Weill Cornell Medical Center in New York. She graduated from New York University in 2018 with a B.A. in philosophy, physics and chemistry.
When she's not at her desk, she's trying (and failing) to raise her online chess rating. Her favorite movies are Dunkirk and Marcel the Shell with Shoes On.
To put it simply, if you were to coat a spoon with the vapid hue, it'd be like creating a spoon-shaped black hole in the middle of your kitchen. Long-term, this incredible color promised to benefit technology like telescopes, cameras and even next-gen iPhones that called for light-blocking capabilities.
But what would happen if we had the exact opposite of the blackest black?
Well, last year, another team of scientists set out to answer precisely that question. Purdue University researchers created the whitest of white, a color that reflected a staggering 98.1% of light. In fact, this effervescent hue was so unique the team earned a spot in the Guinness Book of World Records. Yet, unlike with Vantablack, the promise of paint made with this shade relied on a little adjustment: It needed to be thinner.
The same team behind the world's whitest paint just reformatted its chemistry to make the medium significantly less thick. Now, they say, the special paint is suitable to coat things like cars, airplanes, trains and even T-shirts. In turn, it'd reflect a ton of sunlight from these items, thereby reducing the need for air conditioning.
"This not only saves money, but it reduces energy usage, which in turn reduces greenhouse gas emissions," Xiulin Ruan, a professor of mechanical engineering at Purdue and author of the study, said in a statement. "And unlike other cooling methods, this paint radiates all the heat into deep space, which also directly cools down our planet. It's pretty amazing that a paint can do all that."
"I've been contacted by everyone from spacecraft manufacturers to architects to companies that make clothes and shoes," Ruan said. "They mostly had two questions: Where can I buy it, and can you make it thinner?"
To be clear, it's not commercially available yet. But Ruan said the team is currently trying to figure out how to make it so.
Coloring the world to protect it
At some point in our lives, we absorbed a bit of scientific information about fashion. "Don't wear black when it's hot out, wear white to reflect the heat." It almost sounds like an excuse sometimes, created to get children to wear clean clothes that happen to be white instead of their dirty old Batman shirt for the 14th time.
But it's true.
The color black is more likely to absorb light, and the heat attached to that light, while white reflects both -- and that's exactly why Ruan's paint innovation works.
To create their new iteration of the world's whitest paint, the researchers generated what's called a nanoporous substance, which included hexagonal boron nitride as pigment, a chemical they say is mostly used in lubricants. Just a 150-micron (0.15 millimeter) thick layer of this medium was enough to achieve 97.9% solar reflectance.
"Hexagonal boron nitride has a high refractive index, which leads to strong scattering of sunlight," Andrea Felicelli, a Purdue Ph.D. student in mechanical engineering and author of the study, said in a statement. "The particles of this material also have a unique morphology, which we call nanoplatelets." In other words, according to the team's models, the molecule's hexagonal shape was key. This type of nanoplatelet appeared more effective in bouncing back solar radiation than spherical nanoparticles, which are typically used in other cooling paints.
"That's fine if you're painting a robust stationary structure, like the roof of a building," Ruan said. "But in applications that have precise size and weight requirements, the paint needs to be thinner and lighter." Aka, if we want to lower our air conditioning use in cars or try to mitigate our apartment's power bill by donning a fresh new hexagonal boron nitride-coated wardrobe.
To take things a step further in this regard, the team also incorporated "voids of air" in its paint ingredient list because that makes the goo highly porous (on a really, really fine scale). This lower density, they say, on top of the thinness, made the paint 80% lighter than the barium sulfate version as well.
"An airplane sitting on the tarmac on a hot summer day won't have to run its air conditioning as hard to cool the inside, saving large amounts of energy," George Chiu, a professor of mechanical engineering at Purdue and author of the study, said in a statement. "Spacecraft also have to be as light as possible, and this paint can be a part of that."