I read ther news today, oh boy....
phys.org: World's whitest paint now thinner than ever, ideal for vehicles
Quote:
The original world's whitest paint used nanoparticles of barium sulfate to reflect 98.1% of sunlight, cooling outdoor surfaces more than 4.5°C below ambient temperature. Cover your roof in that paint, and you could essentially cool your home with much less air conditioning. But there's a problem.
"To achieve this level of radiative cooling below the ambient temperature, we had to apply a layer of paint at least 400 microns thick," Ruan said. "That's fine if you're painting a robust stationary structure, like the roof of a building. But in applications that have precise size and weight requirements, the paint needs to be thinner and lighter."
That's why Ruan's team began experimenting with other materials, pushing the limit of materials' capability to scatter sunlight. Their latest formulation is a nanoporous paint incorporating hexagonal boron nitride as the pigment, a substance mostly used in lubricants. This new paint achieves nearly the same benchmark of solar reflectance (97.9%) with just a single 150-micron layer of paint.
...
"The models showed us that the nanoplatelets are more effective in bouncing back the solar radiation than spherical nanoparticles used in previous cooling paints," Katsamba said.
The paint also incorporates voids of air, which make it highly porous on a nanoscale. This lower density, together with the thinness, provides another huge benefit: reduced weight. The newer paint weighs 80% less than barium sulfate paint yet achieves nearly identical solar reflectance.
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So particle shape and entrained air bubbles optimize the performance. The material is obtainable. Car paint typically is 40 microns eac for primer, color and clear coats; so 40 microns for primer and 150 microns for the3 Ulta White.
Then Turtlewax protective coating with graphene for a hydrophobic surface.