A multiwavelength approach for the study of contemporary painting materials by means of fluorescence imaging techniques: An integration to spectroscopic methods

Imaging methods based on visible luminescence induced by ultraviolet (UV) radiation are well consolidated in the investigation of ancient works of art, to map varnishes, retouches, and possibly some pigments. As far as contemporary art is involved, the wide range of synthetic materials, especially pigments, introduced from 1850 onwards, makes the possible application of the technique particularly challenging. Among the colouring substances used by artists in the 19th and 20th centuries, only cadmium-based pigments received attention due to their typical near-infrared luminescence. Nevertheless, the fluorescence emission exhibited by several synthetic pigments upon visible excitation was recently demonstrated and confirmed using UV radiation in the present work. The subsequent possibility of individuating such materials in paintings by ultraviolet fluorescence (UVF) images was explored on mock-up painting samples of a wide series of pigments dispersed in oil or acrylic binder. Visible and infrared luminescence images obtained by irradiating with visible radiation (VIVF and VIL) were also collected. It was thus evidenced the possible advantage of the choice of a different excitation wavelength in discriminating between the contributions of pigment and binder. Finally, a recent oil painting on panel was also examined as case study.