Quantitative approaches for Fiber Optics Reflectance Spectroscopy (FORS)

Ricardo P. Vicente Rojas, Silvia Sotgiu, Véronique Cachia, Eugenio DelRe, Nicola Schiavon, Mauro Giustini, Mauro Missori

Abstract

In this paper, Fiber Optics Reflectance Spectroscopy (FORS) was used to measure the concentration of pigments in paintings on a paper substrate. There is currently no agreement on a general quantitative approach using FORS, even if several attempts have been made in the past with varying degrees of success. In our approach, reflectance spectra were processed using the Kubelka-Munk (K-M) theoretical model of light propagation in an optical inhomogeneous medium. Experimental tests were carried out on mockups prepared using mixtures of two pigments (ultramarine blue and Naples yellow) and their reflectance spectra were acquired using a set-up with an integrating sphere. Given the linear relationship between the scattering and absorption coefficients of the pigments, and knowing the volume concentration of the pigments, the method enables both identification and quantification of components in the binary paint mixtures from FORS spectra.

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IMEKO-Metroarchaeo-2025-048.pdf

DOI

10.21014/tc26-2025.048

IMEKO TC

TC26 - Metrology for Cultural Heritage

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