World's Whitest Paint Is Now Thin Enough to Coat Cars, Spacecraft
We now have the blackest black and the whitest white. What's next?
What's happening
Scientists who made the world's whitest paint just adjusted their formula to make a coating of the substance much thinner.
Why it matters
Covering objects like airplanes, cars and spacecraft with this paint would lower air conditioning use and reduce greenhouse gas emissions.
In 2019, scientists from the Massachusetts Institute of Technology invented the blackest of black. It was a color so unbelievably dark it absorbed 99.9% of all visible light, beating out even the famous Vantablack, a strong ebony that sent the art world into a frenzy.
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.
No problem.
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."
You can check out a detailed outline of their new formula in a paper published Monday in the journal Cell Reports Physical Science.
"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.
The Redemption of Vanity is a work of art by MIT artist-in-residence Diemut Strebe. On the left is a yellow gem. On the right is the same gem covered in the blackest black on Earth. Look again. It's there, I promise.
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.
The bright paint's novel formula contrasts with the team's previous one, which involved barium sulfate, a low-cost, white crystalline powder known for its light reflection capabilities. That version called for a 400-micron (0.4 millimeter) layer to achieve the desired reflective outcome. Pretty hefty for painting stuff when you think about it.
"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.
You can see the team's previous iteration of the white paint on the left, and the new one on the right.
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."