Full-field XRF instrument for cultural heritage: Application to the study of a Caillebotte painting

A novel full-field X-ray fluorescence spectrometer developed for cultural heritage applications is presented. Named "CartiX," it was designed for routine deployment in the field (museum, archeological site) and uses a concept under development at NASA for planetary exploration. CartiX utilizes 2 miniature X-ray tubes, a square pore Micro-channel Plate X-ray Optic, and a direct-illumination CCD camera to collect spatially resolved X-ray fluorescence data from an area of 13 x 13 mm(2). We report here the application of CartiX to the analysis of a Gustave Caillebotte painting directly in the exhibition room. The Impressionists are renowned for their painting technique and their approach in capturing the effects of light in nature through a new use of color. They adopted innovative artistic practices consisting of short brushstrokes of unmixed colors that barely convey forms and give an effect of spontaneity and effortlessness that masks their often carefully constructed compositions. Here, we use high spatial resolution chemical data measured with CartiX to reveal the artist's complex use of pigments and the formation of alteration products and to help in the interpretation of the artist's choice of materials and their manipulation with small and thin brushstrokes.