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

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 techniqu...

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Bibliographic Details
Published in:Molecules (Basel, Switzerland) Switzerland), 2023-06, Vol.28 (12), p.4683
Main Authors: Dal Fovo, Alice, Martínez-Weinbaum, Marina, Oujja, Mohamed, Castillejo, Marta, Fontana, Raffaella
Format: Article
Language:English
Subjects:
Calibration
Chemical composition
Cross-sectional studies
Cultural heritage
Diffuse reflectance spectroscopy
Exponential functions
Incident radiation
Laser induced breakdown
LIBS
Measurement
NMR
Nuclear magnetic resonance
OCT
Optics
Paints
Pigments
Radiation
Raman spectroscopy
Reflectance
reflectance spectroscopy
Spectral sensitivity
Spectroscopy
Spectrum analysis
Stratigraphy
Thickness measurement
thickness measurements
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Summary: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.
ISSN:1420-3049
1420-3049
DOI:10.3390/molecules28124683