Scientists at the Getty Conservation Institute (GCI) in Los Angeles have developed a new method for authenticating historic photographs that could have broad implications for museum collections, art historians, collectors and conservators. The secret they’ve revealed lies deep within the photograph itself – each chemical printing process leaves behind a series of markers that collectively can be as distinctive as a fingerprint, if you know where to find it.
In the past, the accepted methodology for the authentication of photographs has been based on the visual or microscopic inspection of photographic images – never a foolproof process.
Now, using nondestructive X-ray fluorescence spectrometry and Fourier-transform infrared spectrometry analysis, GCI Senior Scientist Dusan Stulik, GCI researcher Art Kaplan, and photographic conservator Tram Vo have been able to successfully identify the hidden chemical signatures associated with different photographic processes and to provide a scientifically-based method for provenancing and authentication of a majority of 20th century photographs.
This development comes at a good time, as with the rise in digital photography, original prints made by seminal artists such as Henri Cartier-Bresson and others of his prominence have skyrocketed in price and desirability.
More than 150 different photographic processes have been tested, developed, and used since the beginning of photography. Photos produced using these processes differ in chemical composition, in internal structure, or both. Analyzing thousands of photographs, GCI scientists found major elements related to various photographic processes such as silver, gold, platinum, iron, barium and strontium, as well as trace elements of aluminum, silicon, potassium, and manganese , among others.
But importantly, they discovered it is the precise measurement of barium and strontium – particularly when compared to the baseline of photographic papers of known provenance collected by the GCI and other researchers – that provides the best clues into the origins of prints.
Both barium and strontium are found in the baryta layer, a mineral coating which began to be incorporated into black and white photographic paper by the end of the 19th century and was in use by nearly all major photograph paper manufacturers until the 1970s. Used to protect the photographic emulsion against impurities from paper, the baryta coating also helped to produce a more brilliant image.
“We’ve found that photographic papers produced by different manufacturers at different times contain distinct concentrations of barium and strontium. These distinctions in the composition of photographic papers and photographs can be used to determine who made the paper, and when,” explained Stulik. “This finding is significant for museum curators, collectors and conservators of photographs because a precise analysis of the baryta layer could, for instance, demonstrate that a photograph in question has been mistakenly identified as being much older than it actually is, or that a certain photographic paper was not actually available during the life of a particular photographer.” Using a multidisciplinary approach – accessing the expertise of the curator, historian and the scientist – is key to the GCI scientist’s success.
Recently, Stulik and Kaplan were invited to Paris to partner with the Henri Cartier-Bresson Foundation and the Atelier de Restauration et de Conservation des Photographies de Ville de Paris in performing chemical analysis on Henri Cartier-Bresson’s original photographs, undertaking the initial work needed to build an archival database for the well-known photographer’s existing prints – against which his other vintage prints could in future be compared.
“Importantly, this new approach is not just a theoretical approach, it’s also practical. It expands our knowledge of Henri Cartier-Bresson’s prints tremendously – his processes, the photographic paper he used, and where and when he printed photographs. We will be much more able to characterize his prints in future. It’s directly applicable,” said Dr. Anne Cartier-Bresson, director of the Atelier de Restauration et de Conservation des Photographies de Ville de Paris, and Henri Cartier-Bresson’s niece. “To my knowledge, this is the first time this type of methodology has ever been applied to this kind of problem. To study one photographer in all of these aspects is unprecedented.”
Added Cartier-Bresson, “There are now many forged copies of photographic prints on the market, so this innovative approach is an important advance for the art market and for collectors and museums. It’s crucial to be able to scientifically analyze prints to be sure they are identified properly. I hope we can continue our collaboration with the GCI to further this important research.”
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