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Update: Worlds Whitest Paint

Researchers are finding that super reflective white paint can be used to keep buildings more cool during summer months. And the bar has been risen, once again!

27 October, 2021

Update on World's Whitest Paint


While it’s not on the market yet, it’s getting closer. We could say “you’re getting warmer,” but we’d be wrong. It’s not getting warmer, it’s getting whiter. We previously reported on a paint developed at Purdue University that used calcium carbonate particles to reflect up to 95.5% of the sun’s rays. More recently, however, a research team at this same West Lafayette, Indiana school has come up with a formula that ups that reflection to about 98.1 percent, meaning it absorbs less than half the solar energy as the earlier version.

This new paint is so white that it even got into the Guinness Book of World Records for the world’s whitest paint — who knew there was even a category? And while that’s a nice perk, the product was developed with a higher purpose in mind. The reflective properties of this new paint, say its developers, might just save the planet from its current climate crisis. According to mechanical engineering professor Xiulan Ruan, by painting even less than one percent of the earth’s surface with this new coating, we might be able to cool the planet and quickly reverse the effects of climate change.

Here’s how it works: the commercial white paint that’s currently in use reflects around 80 to 90 percent of the sunlight that hits it. This can keep the surfaces it’s applied to from getting too hot, but Ruan’s mission was to develop something even more efficient than that. His new paint, about seven years in the making, cuts the heat absorption by as much as 10 times over its current commercial counterpart and can go beyond just keeping a surface from overheating … it can actually lower the temperature of the surface it’s on.


The Barium Difference

It took some work to finally hit that Eureka moment. At first, the team considered over 100 different materials. Eventually they narrowed it down to ten, and even then, the research crew tested around fifty different formulations for each material. 

Finally, Ruan and his team found the successful formula — this paint contains high concentrations of the chemical compound barium sulfate, also used in cosmetics and to brighten photographic paper. Barium is safe enough to ingest, said Ruan’s student Joe Peoples, reminding us that people even drink it when they need to have their bowels x-rayed. 

Featured on a PBS report, Peoples demonstrated two small squares, one painted with the new coating and the other covered with a white paint currently on the market. Not only could you see the difference, but you could feel it, said the reporter. It was about fifteen degrees cooler on a 73-degree day. Peoples suggested than when painted over a larger surface it could eliminate the need for air conditioning in many locales and even cut the need for AC by 75% in hot spots like Phoenix and Las Vegas.

Cool your house with white paint


Lightly Scattered

What makes it successful is the various particle sizes of barium sulfate used in the paint. Different sizes scatter different wavelengths of sunlight, so, according to an article published by the Purdue University News, the wider range of particle sizes allows the paint to scatter more of the light spectrum from the sun. 

Ruan estimates that painting a roof of about 1,000 square feet could provide a cooling power of 10 kilowatts, more than used in most home air conditioning systems. Can we get to 100% reflectivity? Maybe not. Ruan stated that while it was possible to make the paint even whiter, it would compromise too many of its properties. The research team has applied for a patent and is working on a partnership with a major paint company. 

Paint has been used for centuries, maybe even millennia, to keep buildings cooler, and much more recently than ancient Greece or Rome, many major U.S. cities have included “cool roof” coatings in their building codes, with notable energy savings. We’ll keep a lookout for when this hits the market, and from who. Be sure to follow us on social media (see links at the top of this page).


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