How the world’s whitest paint can tackle climate crisis

Paint has potential to cool exteriors of airplanes, cars and trains, scientists point out

A new formulation of the world’s whitest paint is thinner and lighter enough to be used on cars and airplanes for radiating heat away, according to a new study.

The world’s whitest paint, seen in this year’s edition of Guinness World Records as well as the The Late Show With Stephen Colbert, can keep surfaces cool and reduce the need for air conditioning, said scientists, including those from Purdue University in the US.

Its original version used ultrasmall barium sulfate nanoparticles to reflect over 98 per cent of sunlight, cooling outdoor surfaces more than 4.5C below ambient temperature.

However, scientists found that to achieve this level of cooling, a thick layer of at least 0.4mm paint needed to be applied.

“That’s fine if you’re painting a robust stationary structure, like the roof of a building. But in applications that have precise size and weight requirements, the paint needs to be thinner and lighter,” said Xiulin Ruan, a Purdue professor of mechanical engineering and developer of the paint.

The latest formulation, described on Monday in the journal Cell Reports Physical Science, was found to achieve nearly the same benchmark of solar reflectance with just a single 0.15 layer of paint.

This formulation incorporates a substance mostly used in lubricants, a pigment called hexagonal boron nitride, scientists said.

“Hexagonal boron nitride has a high refractive index, which leads to strong scattering of sunlight. The particles of this material also have a unique morphology, which we call nanoplatelets,” said Andrea Felicelli, a Purdue PhD student in mechanical engineering who worked on the project.

Researchers said the new paint also incorporates voids of air that make it highly porous with lower density and thinness, providing the benefit of reduced weight.

They said it weighs 80 per cent less than the barium sulfate paint reported last year but achieves a nearly identical solar reflectance.

“Now this paint has the potential to cool the exteriors of airplanes, cars or trains. 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. Spacecraft also have to be as light as possible, and this paint can be a part of that,” said George Chiu, another co-author of the study.

Scientists hope the paint would help cool surfaces and significantly reduce the need for air conditioning.

“This not only saves money, but it reduces energy usage, which in turn reduces greenhouse gas emissions. 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,” Dr Ruan said.