As it is getting warmer here by the minute I was asking myself:
Are there materials, that are black (in th visible range) but reflect (most) invisible light?
Furthermore, I asked myself what fraction of heat could be kept away using this material in daylight.
For bonus points, it would be great if it could be used as some kind of fabric. I am not looking for a specific material but am curious, as e.g. metals do reflect all light up to a certain frequency and thus would not suffy. Therefore it would be nice to understand the underlying mechanism.
In the winter of course it would be nice to reverse this, so to have white shirts, still getting hot in the sun.