WETZEL, RACHEL. "THE HISTORY OF LIGHT BLEACHING TECHNIQUES USED IN PHOTOGRAPH CONSERVATION AND THE EXAMINATION OF THE SHORT-TERM AND LONG-TERM EFFECTS OF LIGHT BLEACHING SILVER GELATIN PHOTOGRAPHS"

Abstract

Light bleaching can often be a successful means of reducing discoloration products in photographic materials, though its short and long-term effects are unknown. This paper explored the changes that occurred when silver gelatin developed-out photographs that were artificially yellowed by two different methods were subjected to aqueous treatments including water washing, light bleaching and light bleaching with hydrogen peroxide. These samples were evaluated alongside an untreated control to monitor any changes in the strength of the gelatin emulsion, loss of silver density and potential color changes in the light tones and white areas of the photographic image. The samples were evaluated visually and instrumentally after chemical development, after artificial yellowing, after aqueous treatment and finally, after artificial aging. The results of the light bleaching treatments were found to vary depending of the type of yellowing that was induced. To further solidify the results, the experiment was repeated on a set of naturally yellowed silver gelatin photographs, which were found to mimic the results of the experimental sample set used in the controlled portion of this experiment.

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Rachel Wetzel was an ARP fellow from 2005 and 2007. Her strong interest in science and the emergence of light bleaching as a chemical treatment for photographs led to this capstone project. The treatment technique was borrowed from paper conservation and since its long-term effects on photographs are largely unknown, it has been a very controversial treatment for photographs. Currently, Rachel is a photograph conservator for the Conservation Center for Art and Historic Artifacts (CCAHA) in Philadelphia, PA.

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