Illuminating Rembrandt's in : the painting process of Van Ruytenburch's costume.

This study examines Rembrandt's use of to depict the costume of Lieutenant Willem Van Ruytenburch, a prominently lit figure in (1642). As part of , the painting was analyzed using noninvasive imaging techniques, including reflectance imaging spectroscopy (RIS), macroscopic X-ray powder diffraction (MA-XRPD), and macroscopic X-ray fluorescence (MA-XRF). These methods enabled the mapping of the artist's pigment palette, which includes lead white, lead-tin yellow, ochres, vermilion, arsenic sulfide pigments, red lakes, smalt, and azurite. Rembrandt applied these pigments in a consistent, systematic way, combining them in groups to achieve pictorial unity. Notably, arsenic-based pigments were used to capture the warm reflections of gold threads, unique to Van Ruytenburch's costume. MA-XRPD also identified degradation products-mimetite, weddellite, and palmierite-associated with the original pigments. These results provide new insights into Rembrandt's modus operandi and inform understanding of the current condition and implications for its conservation.