Some time ago I put a piece of analog film in a light tight bag and placed a piece of uranium glas on top. After two weeks I developed the film and it is clearly visible where the piece of glass was sitting.

Black and white scan of the piece of negative film, the film strip is almost black, roughly in the middle is a square area that is bright because the radiation from the uranium glass exposed the filmPhoto of the piece of negative film in front of a white background, the film is clear, a square area roughly in the middle is dark grey due to the uranium glas exposing the film
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