Advancing fiber optics reflectance spectroscopy with remote detection

Non-invasive methods are essential for studying materials in cultural heritage artworks. Fibre Optic Reflectance Spectroscopy (FORS) is widely used for in situ analysis of opaque materials in reflectance mode. However, traditional FORS requires direct contact or close proximity to the artwork, limiting its use with fragile or inaccessible objects. This study presents a novel remote FORS method, validated through the analysis of reference coloured cardboards and the painting Saints Peter and Stephen, tentatively attributed to Antonio del Massaro da Viterbo (ca. 1450–before 1516), conserved at the Fondazione Cini in Venice, Italy. A custom optical setup, using a refractor telescope and multichannel spectrometer, acquired Vis-NIR reflectance spectra from distances up to 10 meters. Remote and contact-based measurements matched well, identifying pigments and dyes and validating the method.