INVESTIGATION OF A SURFACE TARNISH FOUND ON 19TH-CENTURY DAGUERREOTYPES
LEE ANN DAFFNER, DAN KUSHEL, & JOHN M. MESSINGER
8 TENTATIVE IDENTIFICATION OF THE FLUORESCENT MATERIAL
The detection of copper and cyanide ion in the SEM and FTIR studies of the fluorescent areas suggests that the fluorescing material might be a copper cyanide compound. This possibility is supported by the observation that, after being separately immersed in aqueous 0.2 M sodium cyanide for .5 minute and then removed, a copper plate fluoresced under UVC irradiation whereas a silver plate did not. In addition, spot tests on several areas of the fluorescing tarnish on actual plates indicated the fluorescing material to be insoluble in water. Although this result is consistent with a water insoluble copper cyanide compound being the fluorescent material of the spots, possibly cuprous cyanide, further analytical work will be necessary to establish this point unambiguously.