Laser-Induced Fluorescence mapping of pigments in a secco painted murals

Laser-induced fluorescence is a remote analysis tool, successfully applied to real-time diagnosis of historical artworks, allowing the observation of features invisible to naked eye, as traces of retouches or presence of modern consolidants. Aim of the present paper is to introduce an historical database of pigments with respective binders and consolidants, realized to support the remote identification and mapping of these materials onto a mural in the least invasive way. To this aim, a monochromatic ultraviolet laser source emitting at 266nm with remote scanning has been used in combination with reflectance. Wall painted models have been built with a secco technique according to traditional recipes of XVII century. Digital image analysis, principal component analysis and spectral angle mapping have been carried out on data to get the mapping of two selected pigments, blue smalt and red carmine, in a real mural painting (XVII century). This non-invasive technique allowed us to operate remotely, a distance up to 11 m from the artwork. Results are consistent with traditional microanalysis performed to identity major pigments.