But, GCI senior scientist Dusan Stulik, who performed the analysis with colleague Art Kaplan, also discovered that, “After pressure mounted to produce additional colors...Hill began adding additional pigments to his color plates by hand, doctoring them to look more multi-hued than the originals."
Eleven years after French artist and chemist Louis-Jacques-Mande Daguerre invented one of the earliest forms of photography, the daguerreotype, in 1839, Hill, of Westkill, N.Y., claimed to have invented a way to produce naturally colored daguerreotypes. But when he refused to release the details of his process until a patent was filed, he was dismissed as an impostor, though no evidence has proved or disproved him a fraud until now.
GCI scientists and curators from the Smithsonian’s photography collection, with help from a 2006 Getty Foundation grant, tested 62 Hillotypes that Hill's son-in-law, John Boggs Garrison, gave to the Smithsonian in 1933 to end the mystery.
The analysis also revealed that many materials, including obscure and dangerous chemicals, and complicated procedures that Hill described as necessary to make hillotypes in his 1856 book were never used to create the images analyzed by the team.
Michelle Delaney, associate curator of the Photographic History Collection at the NMAH, said that the discoveries "will be key to developing a future conservation strategy for the Smithsonian’s Hillotype plates," which feature landscapes around Westkill and images of popular paintings and lithographs.