from New York Times -
Arsenic and Old Photos
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An interesting article on the work of Dusan Stulik at the Getty Conservation Institute on the identification and compilation of materials used in the making of photographs. Dusan's work is in part driven by the ubiquitous popularity of digital photography resulting in "an impending disaster in photographic conservation and scholarship: the abandonment and loss of many decades’ worth of information about traditional photos as the switch was made to digital." The endpoint is a reference publication:

"[...] sometime in the next few years, a door-stopping Atlas of Analytical Signatures of Photographic Processes, a chemical characterization of every known (and, until now, some previously unknown) means of making pictures."

See also information from GCI's website on the Research Project on the Conservation of Photographs.
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