Characterizing the Image Forming Particles of Modern Ungilded Daguerreotypes Using XRD and SEM

: X-ray diffraction (XRD) and high-resolution scanning electron microscopy (SEM) have been used to characterize the silver mercury amalgam particles resting on the surface that comprise the image of five daguerreotype plates that were not gilded and that were prepared by three different contemporary daguerreotype makers. The regions of interest of the surface that were examined were overexposed, solarized, and highlight (white) areas. The XRD portion of the study shows that the two main silver mercury amalgam particles identified using the International Center for Diffraction Data PF4 + database were the Schachnerite/ζ (zeta) phase amalgam, Ag1.1Hg0.9, and the mercury silver amalgam, Ag0.65Hg0.35. On one of the daguerreotypes a third silver mercury amalgam, Moschellandsbergite, Ag2Hg3, was also identified in small concentrations. High-resolution SEM images corroborate the diffraction data and show that the crystalline nature of the silver mercury amalgam particles on all five plates to be mostly hexagonal, which would correspond to the Schachnerite/ζ (zeta) phase amalgam, and fewer rectangular solid and cubic crystals corresponding to the mercury silver amalgam.