Most of us are familiar with the transformational power of Instagram filters such as Amaro and Earlybird, and the magic they can work for our amateur iPhone photography. But what can we learn in an art historical context by making use of traditional camera filters? Multispectral imaging uses cameras that can “see” into the ultraviolet (UV) and infrared (IR) wavelengths along the electromagnetic spectrum, allowing us to photograph features of artworks that are not visible to the naked eye. At the Freer|Sackler, I used the conservation department’s Nikon D100 camera and Kodak Wratten gelatin filters to create UVIR photographs of the museum’s entire collection of watercolors by James McNeill Whistler. These photographs will be used as part of a larger project called Whistler and Watercolor, a collaborative, technical art history research project by an F|S conservator, curator, and conservation scientist.
While most of Whistler’s oeuvre has had the benefit of in-depth study, the watercolors have been waiting for their turn in the spotlight. Whistler created more than three hundred watercolors in his lifetime, most of which were executed in the 1880s, during the height of his fame. Museum founder Charles Lang Freer acquired fifty-two of them. Whistler and Watercolor will provide Whistler scholars and enthusiasts with a technical description of the artist’s working methods in watercolor. Were his materials and techniques similar or significantly different from the way he used other mediums? How do they compare to watercolors by other artists of the time period? Did he follow the methods taught in watercolor manuals and how-to books of the late nineteenth century or was he more innovative and experimental?
Multispectral imaging using traditional photographic filters can help us answer some of these questions. Look at the three images above for an example of a reconstructed nineteenth-century palette (like Whistler’s) photographed normally and then using two gelatin filters with different light sources. Certain pigments exhibit characteristic behaviors in reflected infrared (IR) and ultraviolet-induced visible fluorescence (UV) that allow us to identify them. Cobalt-containing pigments, such as cerulean blue or cobalt green, become transparent and disappear completely in reflected infrared (at approx. 850 nm). With ultraviolet-induced visible fluorescence, red madder lake typically emits a red fluorescent “glow” due to the presence of a compound called purpurin. By using photographic filters, as well as a variety of other techniques to back up these visual observations, it will be possible to reconstruct Whistler’s use of watercolor pigments in the late nineteenth century to aid future research and study.