I had some dealings with IR imaging in the Company I worked for (that was quite a while ago, I have been retired for 22 years). The best white paint (using an Al oxide if I remember correctly) actually looked black at long-wavelength IR (30 microns). Even snow looks black. The Sun's heating that can approach 1KW per square meter is at those long wavelengths. What these guys have achieved is a wide bandwidth reflective paint. I think the UV coatings on sunglasses are not wide band, they are frequency selective where the frequency is determined by the thickness of the coating, just like RF transmission line tuning stubs where the frequency is determined by the length of the stub.
Smudge
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