Interpretation of mid and near-infrared reflection properties of synthetic polymer paints for the non-invasive assessment of binding media in twentieth-century pictorial artworks

The goal of this paper is to evaluate the potential of reflection infrared spectroscopy in discriminating among different binding media in 20th century painting, with relation to distortion effects due to the mixing of surface and volume reflection and potential overlaps by pigment absorption bands. The study was carried out analyzing the reflection infrared properties of modern paint reconstructions including acrylic emulsion, polyvinyl acetate resin, oil-modified alkyd resin and two traditional media (drying oil and proteinaceous tempera) in mixture with a number of pigments selected for their absorption bands and their potential overlaps in the mid and near-infrared regions. Specific spectral markers were determined for each binding medium and then successfully exploited for the interpretation/classification of non-invasive reflection infrared spectra recorded in situ on eleven paintings of the second half of the twentieth century.