Scientists at the Getty Conservation Institute have developed a new chemical analysis technique that could revolutionize the authentication of historic photographs.

In the past, photographs have typically been identified through visual or microscopic inspection, a method that relies on connoisseurship and is not error-proof. Now, the Getty researchers have revealed that most 20th-century printing processes leave behind distinct chemical traces that are nearly as unique as fingerprints.

Scientists Dusan Stulik and Art Kaplan, along with photo conservator Tram Vo, used nondestructive X-ray fluorescence spectrometry and Fourier-transform infrared spectrometry analysis to analyze the chemical signatures of numerous historic photographic processes, of which there have been more than 150 since the beginning of photography. The scientists determined that by precisely measuring the amounts of barium and strontium in a given print — both elements are both found in a mineral coating that became part of black-and-white photographic paper by the end of the 19th century and would remain part of nearly all paper manufactured until the 1970s — they could determine its origin.

“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] could 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.”