Spectroscopic analysis of hand-colored photographs and photographic hand-coloring materials

Hoppe, Jonathan
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University of Delaware
Prior to the advent of color photographic processes, the only method of producing photographs in color was to apply coloring agents by hand. Though handcolored photographs from every period of photography can be found in public and private collections throughout the world, little research has been done in developing methods for identifying the coloring agents on such photographs. The first aim of this research was to determine if spectroscopic methods—X-Ray Fluorescence Spectroscopy, Fourier Transform-Infrared Spectroscopy, Dispersive Raman Spectroscopy, Scanning Electron Microscopy-Energy Dispersive Spectroscopy, and Gas Chromatography-Mass Spectrometry—could be used to identify the components and pigments in period Marshall’s Photo-Oils kits, which were immensely popular after their introduction in the 1920s and are still produced today. After successfully identifying the primary components of these paints, the next goal of the research was to determine which, if any, spectroscopic methods could be used to best identify these same paints when painted onto a photographic base. Finding that using XRF and Raman spectroscopy used in conjunction with one another was the best method for this task, photographs colored with unknown coloring media were examined to see if these same methods could then be used to identify the colorants. Early results are quite promising, though further research is needed.