[freebeard]

Further to the original post:
gizmodo.com: Just How White Can White Paint Get?
A team from Purdue University is using nanotechnology to create paints that reflect 98% of sunlight.

“We definitely had some issues getting the particles to incorporate fully into the paint mixture,” Felicelli said. “But over time, we were able to resolve those different processing techniques. And we were able to achieve an application that was very similar to your regular commercial white paint.”

The resulting paint using boron nitride is nearly as effective as the first formulation with barium sulfate: It can reflect up to 97.9% of sunlight. What’s more, it only requires a 0.15 millimeter layer to be effective, and, thanks to the compound’s porous structure that incorporates a lot of air, weighs 80% less than the barium sulfate paint.

While you can’t go out and buy this ultra-white paint right now, Ruan said the team is in talks with manufacturers to begin the process of creating and selling it as a product. The paint is also being perfected and tested to ensure it can resist dirt and can last as long under UV light as commercial white paints. Down the road, Ruan said, he’s also interested in creating reflective paint in different colors, as well as paints that could switch from reflective to absorptive, depending on the season—like a building-size version of drinkware that changes color when you pour hot or cold water into it.

“Right now, the paint is for cooling, so it’s great for hot climates,” he said. “But in Indiana, for example, we need heat in the winter. It would be great if you were able to switch from the whitest paint in the summer to a color that can absorb sunlight. That is challenging to make it cost effective, to make it scalable. We are investigating, and we can’t expose all the details now, but we can learn from nature to help us understand how to make those kinds of technologies possible.”