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"Cool Coat" -- The Discovery Files

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Columbia engineers have made white paint whiter -- and cooler -- by removing white pigment, and have invented a polymer coating, with nano-to-microscale air voids, that acts as a spontaneous air cooler and can be fabricated, dyed and applied like paint. Research in Arizona showed that the coating reduced air temperatures under the coated surface by 11 degrees, which suggests the coating could help stem energy costs from cooling in a rapidly warming world.

Credit: NSF/Karson Productions

Audio Transcript:

A whiter shade of cool.

I'm Bob Karson with the Discovery Files, from the National Science Foundation.

(Sound effect: bacon frying) Can't stand the heat? Paint the house. Or the car or the spacecraft. Researchers at Columbia University have developed a high performance exterior polymer coating that goes on any surface conveniently as paint. It achieves a high degree of what's called "passive daytime radiative cooling." The principle is not new. But what is, is the degree to which it's effective.

If you paint a surface white, it will reflect more sunlight back into the atmosphere. But even white paint usually has pigments that absorb UV light, and don't reflect solar wavelengths very well. The new coating contains no pigments not even white.

When the coating dries it has tiny air voids that make it look white. They act as an air cooler, and simultaneously reflect sunlight and radiate heat into the cold sky. Result? A net heat loss.

How much cooling down can the coating do? In tests in foggy, tropical Bangladesh, things were more than 5 degrees Fahrenheit lower under the coated surface than in the air around. And in the warm, arid desert climes of Arizona, almost 11 degrees lower.

The team is in talks with industry about the next steps.

In a world of rising temperatures and massive energy usage, this is definitely; one cool technology.

"The discovery files" covers projects funded by the government's National Science Foundation. Federally sponsored research -- brought to you, by you! Learn more at or on our podcast.

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