"It started with [KB9ENS] looking into paints or coatings for passive or
radiative cooling, and in the process he decided to DIY his own. Not only is it
perfectly accessible to a home experimenter, his initial results look like they
have some promise, as well.
[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.
What really got [KB9ENS] thinking was that at its core, the passively-cooling
paint in the research is essentially a whole lot of different particle sizes of
barium sulfate (BaSO₄) mixed into an acrylic binder. These two ingredients are
remarkably accessible. A half-pound of BaSO₄ from a pottery supply shop was
only a few dollars, and a plain acrylic base is easily obtained from almost any
paint or art supplier.
[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. He wetted
the BaSO₄ with some isopropyl alcohol to help it mix into the base, and made a
few different concentrations. A 60% concentration by volume seemed to give the
best overall results."
Via Susan ****
Share and enjoy,
*** Xanni ***
Chief Scientist, Xanadu
Partner, Glass Wings
Manager, Serious Cybernetics