Reflectance Spectroscopy as a Novel Tool for Thickness Measurements of Paint Layers

Year: 2023

Authors: Dal Fovo A., Martnnez-Weinbaum M., Oujja M., Castillejo M., Fontana R.

Autors Affiliation: CNR, Ist Nazl Ott CNR INO, Largo E Fermi 6, I-50125 Florence, Italy; CSIC, Inst Quim Fis Rocasolano, C Serrano 119, Madrid 28006, Spain.

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 (12)      Pages from: 4683-1  to: 4683-17

More Information: This research was funded by the Spanish State Research Agency (AEI) through project PID2019-104124RB-I00/AEI/10.13039/501100011033, by project TOP Heritage-CM (S2018/NMT-4372) from Community of Madrid, and by the H2020 European project IPERION HS (Integrated Platform for the European Research Infrastructure ON Heritage Science, GA 871034).
KeyWords: paintings; reflectance spectroscopy; OCT; LIBS; Raman spectroscopy; thickness measurements
DOI: 10.3390/molecules28124683

Citations: 7
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