bitume de Judée

DEF: Vernis artificiel constituant un enduit hydrofuge employé en photogravure.
OBS: Cette propriété, qui a été utilisée par Nicéphore Niepce pour ses premières expériences, est à l'origine de la photographie. Le dépouillement était effectué à l'essence de lavande ou à l'essence de térébenthine.

CONT: Niépce used pewter plates in his lithography business, and used various light-sensitive varnishes and pitches as a coating on the metal to record the image. His first success, 1826-27 was with bitumen of Judea coated on a pewter plate. It took 8 hours of exposure to differentially harden the coating, which was washed in oil of lavender diluted with white petroleum. The exposed areas were hardened and did not dissolve; unexposed areas remained soluble and were removed.
CONT: The process [Joseph Niepce] developed used a metal plate coated with a thin layer of asphaltum (bitumen of Judea), which became insoluble after exposure to light.