Development of defocusing micro-SORS mapping: a study of a 19 th century porcelain card

Defocusing micro-spatially offset Raman spectroscopy (micro-SORS) is a recently developed technique that was proven to be successful in cultural heritage research to investigate non-destructively the stratigraphy of turbid or semi-transparent paint layers. However, until now this approach has not been applied to obtain imaging information with inhomogeneous real samples. In this work, a defocusing micro-SORS mapping approach is demonstrated with a 19th century porcelain card as a tool to study inhomogeneous painted stratigraphies; the depth information obtained with averaged defocusing sequences was combined with the lateral and spatial distribution achieved by mapping the painted zones. The effectiveness of the technique was verified by analysing an area where a partial overlapping of red (vermilion), blue (Prussian blue), green (chrome yellow and Prussian blue), and brown (vermillion and carbon black) pigmented zones is present, on top of a white (lead white) preparation layer.