Making Infrared Cooling Paint From Grocery Store Items (w/Novel CaCO₃ Microsphere Synthesis)

There's an interesting guide on how to make radiative cooling paint from common ingredients complete with an explanation why it works: ▶ this video The catch is that such paint is not particularly robust, much less weatherproof. Beats yogurt I guess, which tends to smell as it turns in sunlight. I have roof windows and was wondering how much I could gain from panels painted like that, but most likely as much as I would using the next best thing - a window sunshade, which I'm using already.

It's a thing in from thousands of years ago link and today link for PDRC there are a couple good videos about it from NightHawkInLight link , ▶ this video and Tech Ingredients link link

You might like NightHawkInLight's videos on the topic[0] and Tech Ingredients[1] - they've been working on making paint using this technology with an at-home DIY process and experimenting with it. [0] ▶ this video [1] link

The youtuber NightHawkInLight made a video about a similar coating (he is using CaCO3 whereas this here is using Al2O3) ▶ this video It was also discussed here link Would be interesting to know how the performance compares.

I want to point out that to optimize for temperature reduction, you want to minimize absorption while maximizing thermal radiation. This says you want the surface to be reflective at wavelengths below some cutoff, but perfectly emissive (that is, black) above that wavelength. (Actually it's a bit more complex, because the atmosphere emits IR in some bands.) Some work on surfaces of this kind have shown promising results, being able to fall below ambient temperature even in full sunlight. Do it yourself: ▶ this video

Weirdly, you can already get decent results with a material that can be prepared at home: ▶ this video It doesn't have all the properties necessary to call it paint, but apparently it does the job.

Here is a frankly incredible video of how you could make such a paint if you were so inclined. I don't think it's very practical, but the video is very interesting anyways ▶ this video

If you want to experiment with making your own radiative cooling coatings with easily available, safe materials and common household tools, this video is a great guide: ▶ this video