Objective: This project is aimed at identifying and mitigating the cause of extreme fading on a group of early salted paper photographic prints. The investigation may have bearing on a broader range of materials that are potentially in danger of similar effects.
Background: Several photographic techniques are associated with the invention of photography. One of these is the salted paper print, which was invented by William Henry Fox Talbot in 1839. The technique consists of producing a silver image on paper that is directly sensitized with silver salts. Fixing of the image, i.e., removal of unexposed silver salts, was done by washing them in a thiosulfate solution. Salted paper prints by Talbot and his circle are among the most prized early photographic works, due to their rarity as well as their often-ascribed painterly images.
Left: Salted paper print by Talbot created ca 1844. (Click on image to view online from The Library’s Prints and Photographs’ online collection)
Four early salted paper prints in the collection of the Library of Congress, two by Talbot and two re-attributed to his collaborator Calvert Jones, were recently discovered to display some unusual and disturbing deterioration, which appears as extreme localized image fading in the shape of the paper hinges holding the prints to their backing boards. This deterioration thus appears to be directly related to contact with the thin, bleached wood pulp hinge paper and/or the hinge adhesive, which were most likely applied shortly after the prints were acquired by the Library of Congress in 1968. Known paste recipes used at the Library at this time suggest that the mounting adhesive most likely consists of wheat starch paste with the addition of a fungicide.
Analytical Investigation: The localized nature of the fading noted on two Talbot and two Jones salted prints suggests that the silver is being attacked by substances in the hinge assembly. Investigation into the cause of this deterioration aims to answer why and how the silver is being attacked, what factors in the housing and/or storage have contributed to interaction between an oxidant and the silver image, and, most importantly, how to stabilize the images. Non-invasive, non-contact X-ray fluorescence (XRF) spectroscopy was initially conducted to acquire elemental information about the materials present in the faded areas as well as the remainder of the image. Results show that the faded areas and the hinge paper both correlate with elevated levels of sulfur, which may be a factor in the deterioration, although this has not been established yet. On-going analysis of expendable hinges, paste, and support materials are expected to shed more light on this degradation phenomenon.
Right: Salted paper print by Talbot created 1842 showing a piece of lace. (Click on image to view online from The Library’s Prints and Photographs’s online collection)
