Physautotype

Hoping to shorten the exposure time of his bitumen process, Niépce decided in 1829, to associate Daguerre to his research.

Once it's completely dry, the alcohol evaporation leaves a residue of tiny dispersed resin particles that give the plate a white, blurry appearance.

[6] The photosensitive agent of this process fine-tuned by Niépce and Daguerre in 1832 was the residue of lavender oil distillation.

The process gives directly positive images, since the white deposit remains on the plate, at places that were touched by light, while the kerosene fumes render transparent the zones that were not illuminated.

However, with the effect of reflections on the metal appearing at places where the white deposit has become transparent, images can be seen as positive or negative.