Quote Originally Posted by AgX View Post
I assume typically it is the other way round, with visible light being reflected. Anyway, a good designed slide projector cools by means of air stream the lamp, the lamp housing, the IR filter in the lighting beam and the slide itself.
From wikipedia (http://en.wikipedia.org/wiki/Hot_mirror): "A hot mirror is a specialized dielectric mirror, a dichroic filter, often employed to protect optical systems by reflecting infrared light back into a light source, while allowing visible light to pass." A cold mirror, according to wikipedia (http://en.wikipedia.org/wiki/Cold_mirror), "A cold mirror is a specialized dielectric mirror, a dichroic filter, that reflects the entire visible light spectrum while very efficiently transmitting infrared wavelengths."

I looked it up after I saw your post because I thought you were right and I had it backward. No biggie 'cause I'm not designing, building, or repairing slide projectors, just using them.