INVESTIGATION OF A SURFACE TARNISH FOUND ON 19TH-CENTURY DAGUERREOTYPES
LEE ANN DAFFNER, DAN KUSHEL, & JOHN M. MESSINGER
10 SUMMARY OF OBSERVATIONS AND FINDINGS
One hundred and ten daguerreotypes have been examined in this study under short-wave ultraviolet illumination. Of these, 50 showed some degree of visible fluorescence. The plates that showed signs of overcleaning, prolonged exposure to the environment, and general mishandling had developed advanced stages of the fluorescence. Several plates that retained old seals virtually intact also showed fluorescence, but only to a very slight degree. While no definitive conclusion can be made at this time, a direct correlation may exist between the extent of handling and exposure to the environment with the degree of fluorescence present. The following list summarizes the principal observations of this study:
- To date, the fluorescence has only been observed on daguerreotype plates. It has not been found on any other photographic medium, including ambrotypes and gelatin silver prints.
- The fluorescence is visible only under short-wave ultraviolet illumination of bare, unglazed plates.
- Areas that fluoresce are not always visible under normal viewing conditions.
- Fluorescence can occur in a variety of patterns and is frequently associated with both localized and generalized areas of physical and chemical deterioration.
- Fluorescence is common, appearing on 50% of the plates examined in this study.
- FTIR analysis indicates the presence of cyanide compounds in the fluorescing areas.