There are some interesting buried comments in a Mar 22, 2019 Artsy article by Karen Chernick on the collection of Michael Mattis and Judy Hochberg (now on display at the Barnes Foundation), which briefly describing a few modern methods of detecting 19th and early 20th C photographic fakes and reprints. The two collectors developed the techniques in consultation with a paper conservator.
The Collecting Couple Who Became Sleuths of Photographic Forgery
When the duo started their collection, prices were rising at a fever pitch, but the market had few safeguards for determining whether or not a photograph was actually vintage. The need for dating tools became evident in the late 1990s, when a suspicious number of purportedly vintage prints by Lewis Hine—an American photographer who recorded child labor conditions and made portraits on Ellis Island—flooded onto the market.
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The couple determined that their purportedly vintage Hine photographs were posthumous in part because the paper was bleached, a practice that only began in the 1950s when manufacturers began adding optical brighteners to paper.
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Messier, Hochberg and Mattis’s collaborator on the scientific tests, also developed a watermark cheat-sheet to help determine the age of photographic paper. The Agfa logo, for example, has changed over the years, and knowing the year range for a particular version can help date a photograph. The tools Messier helped the couple develop for their own collecting purposes have now become industry standard.
