Visited Santorini earlier this year – beautiful place. Temperatures on average during the day were about 25C in direct sunlight. I noticed a lot of the buildings/railings are coated in a white paint and surprisingly were cool to the touch. Like, not just comfortable by straight up cold even in the beating sun. This can’t just be part of the natural reflective qualities of using white, can it?
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It can be, with the right paint.
Things can heat up either with contact with something hot (and conversely cool down by touching something cold) or by absorbing radiation.
So if a white paint reflects enough sunlight (visible and infrared) that it sheds more heat than it absorbs, it can even be cooler than surrounding air. Put it on something that can absorb lots of heat before noticeably raising in temperature (say, over the course of the day), like stone or metal, and the surface will feel cool even with a middling white paint. Because it’s cooled from one side but not heated fast enough from the other.
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