It started with [KB9ENS] looking into paints or coatings for passive or radiative cooling, and in the process he decided to DIY his own. [KB9ENS] read about a type of ultra-white paint formulation that not only reflects heat, but is able to radiate it into space, cooling the painted surface to below ambient temperature. This is intriguing because while commercial paints can insulate and reflect heat, they cannot make a surface cooler than its surroundings. [KB9ENS] decided to mix up a crude batch of BaSO₄ paint, apply it to some things, and see how well it compared to other paints and coatings. Actual passive cooling can do more than just keep something less warm than it would be otherwise.

Source: The Guardian July 22, 2023 15:01 UTC