I just though of this. After reading the wikipedia article on thermal paper I'm left with the conclusion that it could be, albeit with some magical chemical voodoo. I'm no chemist and cannot think of a way to do this, but maybe a positive would be more practical to achieve. Say we heat a sheet of thermal paper until it's completely exposed. Then put that in a camera on a bright day and leave the UV to bleach the paper. It could take days, but at least it relies on total received exposure, not on light so bright that it raises the temperature of the coating above it's threshold.
Any ideas? I'm guessing this medium would be super contrasty, but who knows...
Not directly as the paper responds to heat and not visible light. Not even radiation in the near infra-red would have any effect. Remember you can load these printers in the light. The paper that I a familiar with contains a pigment like lamp black encapsulated in a white waxy coating. When heated the pigment is exposed. This will not fade on exposure to UV light. Other pigments may have a similar problem.
I'm sure if you focus the sun on the paper it will leave a mark (think burning things with a magnifying glass). Check out Chris McCaw's work called Dead Link Removed--not exactly what you're thinking of doing, but kind of.
I'm sure if you focus the sun on the paper it will leave a mark (think burning things with a magnifying glass). Check out Chris McCaw's work called Dead Link Removed--not exactly what you're thinking of doing, but kind of.
A singed track of the Sun's path doesn't count as a visual image? Perhaps you (and the OP) meant a realistic image. I think exploring alternative media is great, but one should probably expect alternative results as well.