The question I was really asking was answered by this: https://physics.stackexchange.com/questions/159856/why-is-black-the-best-emitter https://physics.stackexc

The question I was really asking was answered by this: https://physics.stackexchange.com/questions/159856/why-is-black-the-best-emitter https://physics.stackexchange.com/questions/159856/why-is-bl... I.e. surfaces which are good at absorbing radiation are also good at emitting, which I didn't know.