Application of ATR-FTIR mapping to identification and distribution of pigments, binders and degradation products in a 17th century painting

Abstract

Attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) and optical microscopy were applied to identify pigments, binders, fillers and degradation products in the 17th century painting 'The Coronation and Assumption of the Blessed Virgin Mary’. This piece of art is located in the Convent of the Sisters of St. Catherine in Orneta (Poland). The main important aspect is the non-destructive character of the examination and the small amount of sample necessary for analysis. Individual layers of five micro-samples cross-sections and powder samples taken from discrete and representative areas of the painting were studied. The combination of a linear array detector with a micro-ATR imaging accessory provides the possibility to overcome the diffraction limit and deliver a spatial resolution of about 5 microns (pixel size at the sample equal to 6.25 μm). Noteworthy, a rich palette of white, blue, red, and black pigments was characterized in the analyzed areas. Additionally, the mapping mode provided information about the distribution of individual components in the paint cross-sections. The analysis made it possible to identify binding media, such as proteins, triglycerides, fatty acids or resin acids, and degradation products, including whewellite, moolooite, and lead soaps.