What do soil and 18th century paint have in common?

​What do soil and 18th-century paint have in common? Quite a lot, according to a recent paper published by WUDPAC Affiliated Professors Dr. Rosie Grayburn and Matt Cushman in collaboration with Mina Porell (WUDPAC ’18) and the Sparks Research Group (UD Department of Plant and Soil Sciences​). Their research question arose from the poor condition of orpiment-containing areas of two 18th-century Philadelphian portraits in the collection at Winterthur Museum. Orpiment (As2S3), a bright yellow pigment, is known to degrade to a colorless form, and this degradation can have a negative impact on the surrounding binder, necessitating alternative treatment approaches. After locating all the arsenic using scanning macro X-ray fluorescence​ (MA-XRF) at Winterthur Museum, the Sparks Research Group took several cross-sections to Brookhaven National Lab to obtain information about the orpiment degradation process in these paintings using micro-X-ray absorption near-edge structure (micro-XANES) spectroscopy​. The techniques used on these cross-sections are the same techniques used to learn about arsenic contamination in soils.​ This collaborative research between has now been published in X-ray Spectrometry Journal; the paper is part of a special issue celebrating the MA-XRF conference held in the Netherlands in September 2022.