Calcium sulfate fillers and binders in Portuguese 15th and 16th centuries: Ground layers from a family painting workshop - Study by multianalytical spectroscopic techniques

The cross-sections from the groups of paintings were examined by optical microscopy and the results were integrated through the analysis obtained by μ-X-ray diffraction, scanning electron microscopy with energy dispersive X-ray Spectrometry, μ-confocal Raman and occasionally with μ-Fourier transform infrared spectroscopy imaging. Ground layers are of calcium sulfate, present as gesso grosso (mainly anhydrite with small amounts of gypsum) in the first and last phases of the workshop and gesso mate (mainly gypsum with small amounts of anhydrite) in an intermediate period. Binders have protein and oleic characteristics.