Analysis and Treatment of a Painting by Kees Van Dongen: Ftir and Elisa as Complementary Techniques in the Analysis of Art Materials

Recent examination and treatment of the Worcester Art Museum’s Reclining Nude, c. 1925, oil on canvas, by the Dutch-born Fauve artist Kees Van Dongen (1877-1968) indicate that the artist used unorthodox materials and techniques, including selective varnishing to adjust color saturation and surface sheen. Examination also revealed resinlike beads exuded from unvarnished passages of paint considered artist-applied retouches. ATR-FTIR micro-spectroscopy of the exudate suggests the presence of gum arabic and sucrose, two common components in watercolor formulations. In order to verify the presence of gum arabic in the exudate, a newly developed ELISA protocol was used, which confirmed the presence of gum arabic. This may indicate that the artist modified his oil paint with gouache or watercolor, ultimately resulting in phase separation and subsequent beading up of water-soluble components from within the paint’s predominantly oil component. The identification of water-soluble materials within an otherwise non-water-soluble paint surface proved critical in formulating an appropriate cleaning approach. Although the exact cause of the exudate is debatable, it serves as a cautionary note for conservators faced with the challenge of treating paintings by Van Dongen.