We did a thing with dry iceand a slide projector in the 70's. A sort of gutter up near the ceiling with a warm water tank which someone had to pull on a bit of string to release the water on the ice which formed a sort of invisible screen, then another bloke projeted a picture of a rainbow onto it. It worked quite well. A bit Heath Robinson but looked really good.
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Captn Hood-Butter is not dead yet.,
Sat 12 May 2012, 14:39,
archived)