Making Infrared Cooling Paint From Grocery Store Items (w/Novel CaCO₃ Microsphere Synthesis)
Why Hacker News recommends it
It comes up whenever radiative cooling coatings are in the news, as a hands-on DIY guide that shows the approach working with household materials.
What it is
NightHawkInLight shows how to make radiative sky cooling paint from grocery and hardware store materials, including a novel calcium carbonate microsphere synthesis. The paint can cool a surface below ambient air temperature in direct sunlight without electricity.
Recommended by 5 HN commenters across 4 different months, 2023 to 2026.
What Hacker News said
Strong rec mkeedlinger · 2023-07 · on “Scientists at Purdue have created a white paint that can cool a building”
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]
Recommends K0balt · 2023-07 · on “To Help Cool a Hot Planet, the Whitest of White Coats”
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]
Recommends Tade0 · 2023-07 · on “To Help Cool a Hot Planet, the Whitest of White Coats”
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.
Recommends slimsag · 2024-03 · on “Using a solar oven as a radiant refrigerator at night”
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]
Recommends energ8 · 2025-06 · on “NASA's Voyager Found a 30k-50k Kelvin "Wall" at the Edge of Solar System”
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]
Recommends Tade0 · 2026-06 · on “UK professor says smearing yogurt on your windows can cool your home”
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.
Cites pfdietz · 2023-09 · on “Is air conditioning making cities hotter?”
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]
Cites jona-f · 2023-11 · on “Ultra-white ceramic cools buildings with record-high 99.6% reflectivity”
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.