Reflectance Spectroscopy as a Novel Tool for Thickness
Measurements of Paint Layers
Year: 2023
Authors: Dal Fovo A., Martínez-Weinbaum M., Oujja M., Castillejo M., Fontana R.
Autors Affiliation: Consiglio Nazionale delle Ricerche-Istituto Nazionale di Ottica (CNR-INO), Instituto de Química Física Rocasolano, Spanish National Research Council (CSIC),
Abstract: A major challenge in heritage science is the non-invasive cross-sectional analysis of paintings. When low-energy probes are used, the presence of opaque media can significantly hinder the penetration of incident radiation, as well as the collection of the backscattered signal. Currently,
no technique is capable of uniquely and noninvasively measuring the micrometric thickness of heterogeneous materials, such as pictorial layers, for any painting material. The aim of this work was to explore the possibility of extracting stratigraphic information from reflectance spectra obtained by diffuse reflectance spectroscopy (DRS). We tested the proposed approach on single layers of ten pure
acrylic paints. The chemical composition of each paint was first characterised by micro-Raman and laser-induced breakdown spectroscopies. The spectral behaviour was analysed by both Fibre Optics Reflectance Spectroscopy (FORS) and Vis-NIR multispectral reflectance imaging. We showed that
there is a clear correlation between the spectral response of acrylic paint layers and their micrometric thickness, which was previously measured by Optical Coherence Tomography (OCT). Based on significant spectral features, exponential functions of reflectance vs. thickness were obtained for
each paint, which can be used as calibration curves for thickness measurements. To the best of our knowledge, similar approaches for cross-sectional measurements of paint layers have never been tested.
Journal/Review: MOLECULES
Volume: 28 Pages from: 1 to: 17
KeyWords: paintings; reflectance spectroscopy; OCT; LIBS; Raman spectroscopy; thickness measurementsDOI: https://doi.org/10.3390/ molecules28124683