Make Your Own Super-reflective Cooling Paint

Barium sulfate (BaSO₄) is an inorganic compound which is plentiful, inexpensive, and so nontoxic and safe it is used, in the form of a milkshake, as a radiocontrast agent for X-ray imaging of humans’ gastrointestinal tracts.

In its pure form, it is a colourless crystal, but when prepared as nanoparticles with sizes varying from ten to hundreds of nanometres, it emits thermal infrared radiation at wavelengths corresponding to around room temperature with an efficiency of more than 96% while, simultaneously, reflecting more than 99% of visible light and a total of 98.1% of all solar radiation (including infrared and ultraviolet light).

Mixed with a carrier solvent and applied as multiple layers of paint, the resulting surface reflects so much incident sunlight and radiates infrared to the sky that the surface will have a temperature substantially below that of the ambient air (the better it is shielded from infrared radiated by surrounding objects and air currents, the greater the temperature difference).


$300 to $500 per ton, although the shipping will raise that a little. The heating needs here are minuscule, it’s all A/C in SW FL.

It’s $5/pound plus $20 shipping on Amazon US, although the reviews say it’s an ineffective hair remover (some youtube thing). That seems like a plus, wonder how painting it on a bald head would work out?


Neither of these vendors specifies the size of the particles in the powder and/or whether the product includes a mix of particle sizes. As explained in the video, for best packing in a thin film of paint applied in multiple coats, the best reflectivity is obtained when the particles are a mix from 10 to hundreds of nanometres in size, as that allows them to more completely fill space. Commercially available pigment intended for passive cooling has such a mix of particle sizes, but it is expensive.


?So how would that affect automobiles. It seems cars sold in warm climes would run cooler, requiring far less A/C.

?Can this stuff be incorporated into leather or other seat materials. Imagine a car in FL, GA, LA, TX, NM, or AZ with such tech.

And I can’t help but ask, ?does it affect radar reflection.

Even if it could be (you’d have to happy with intense white as the only colour available), it wouldn’t help because the infrared it radiates would be captured by the glass of the windows and radiated right back into the cabin, heating the air—a real greenhouse effect.

Probably not. The reflectivity of the paint works because the wavelength of light is on the order of the size of the particles of barium sulfate coating the surface. Radar uses much longer microwave wavelengths which would probably not “see” the coating at all, but bounce off whatever it was applied to. The radar absorbing material used on stealth aircraft generally uses some kind of conductive material, such as tiny spheres of iron or ferrite, which absorb the incident microwave energy, essentially “shorting it out” and converting it to heat, which is conducted to the skin of the plane and dissipated.

The super-reflective paint would do an excellent job of reflecting the visible or infrared beam emitted by a laser speed gun and increase its detection range.


Wouldn’t want that, now would we. :laughing: