Energy-optimized synchrotron XRF mapping of an obscured painting beneath Exit from the Theater, attributed to Honoré Daumier

Abstract

Exit from the Theater, in the collection of the Nelson-Atkins Museum of Art, Kansas City since 1932, has long been attributed as a late work by Honoré Daumier completed around 1863. The painting, on a reused panel of tropical hardwood, is based on a portion of a Daumier print, and microanalytical studies confirm that the palettes of the theater scene and an underlying landscape are both compatible with the 1863 date. However, direct connection between the artist and the painting has never been established. The landscape, and any connection it might offer to Daumier, cannot be revealed by radiographic inspection due to an intervening layer of lead white paint.Macroscopic XRF (MA-XRF) mapping to clarify the underlying composition was initially carried out using a tube-based system; however, the limited number of detectable elements and dynamic range were insufficient to depict an understandable image. Scanning electron microscopy and elemental analysis of cross sections guided the optimization of further MA-XRF scans using monochromatic excitation and the Maia detector at beamline A2 of the Cornell High Energy Synchrotron Source. Scans were performed at two different energies, first at 12.9 keV, below the lead L3 edge (13.035 keV), and second at 38.5 keV, above the barium K edge. Areas of interest were studied with scanning x-ray diffraction (MA-XRD) at 38.5 keV.Synchrotron MA-XRF imagery and MA-XRD data have opened promising avenues for clarifying the authorship of Exit from the Theater. New details in the copper, arsenic, tin, cadmium, and antimony XRF maps revealed a previously concealed mountainscape, rendering the landscape recognizable as a view sketched by explorer John Hanning Speke during his expedition to the source of the river Nile (1857–59). Identification of the landscape has led to inquiries into artists in Daumier's circle connected with the French publication of Speke's journal. Furthermore, a replication experiment, MA-XRF, and MA-XRD confirm that an unusual texture observed in radiography, resembling paint spread by a brayer rather than brush, arises from the intervening lead white layer. We also demonstrate the use of synchrotron MA-XRD as a non-sampling probe of paint stratigraphy, locating an ambiguous XRF feature to the theater scene stratum. These observations of technique, combined with pigment microanalysis, will inform the relationship of Exit from the Theater to Daumier's oeuvre.