Wikipedia
The physautotype (in French, physautotypie) was a photographic process, invented by Joseph Nicéphore Niépce and Louis Daguerre in 1832, in which images were produced by the use of lavender oil residue dissolved in alcohol as the photographic agent. The solution was coated onto a metal or glass plate and allowed to dry, after which it had a powdery white appearance. The plate was then exposed in a camera obscura for several hours and developed with solvent vapors, which caused the least strongly exposed areas to become proportionally more transparent, creating a photographic image that was positive when viewed against a darker background. The results were reportedly not durable, tending to become entirely transparent over time even if kept in the dark, but additional chemical processing to proportionally etch or darken the underlying surface could be used to "fix" the image.