Biography provided by the Patrick Montgomery Collection (Archive Farms)
 
Alphonse Louis Poitevin (1819 -1882) was a French chemist, photographer and civil engineer who discovered the light–sensitive properties of bichromated gelatin and invented both the photolithography and collotype processes. He has been described as "one of the great unheralded figures in photography". In the 1850s he discovered that gelatin, in combination with either potassium or ammonium bichromate, hardens in proportion to the amount of light that falls on it. This discovery was later used by numerous inventors such as Josef Albert, Joseph Wilson Swan, Paul Pretsch and Charles Nègre to develop subsequent photographic printing processes such as heliogravure, photogravure, collotype, autotype and carbon printing. This heliogravure, a reproduction of an engraving by Charles Emile Jacques and one of Poitevin’s earliest, has been reproduced in many early Histories of Photography including those by Figuier (1867), Davanne (1882), Eder, (1905) and Lecuyer (1945).