Degradation study of pigments through transient absorption and colorimetry

Francesca Assunta Pisu, Pier Carlo Ricci, Carlo Maria Carbonaro, Daniele Chiriu

Abstract

The application of non-destructive techniques in the field of cultural heritage is becoming fundamental to understanding degradation phenomena. In this study, Transient Absorption (TA) spectroscopy and colorimetry were exploited to explain the process which causes the degradation of some pigments, like Red Vermilion and cadmium yellow. The optical properties involved in the process are studied before and after exposing the pigments to UV light (365 nm). The study was carried out with particular attention to the ground state bleaching signals, directly connected to the formation of intragap trap levels responsible for the pigment degradation. First derivative reflectance spectra reveal the presence of these defects in the cadmium yellow, while the analysis of Tauc plots from Kubelka Munk function confirms the reduction of energy band gap due to UV exposure in the case of Red Vermilion. Transient Absorption turns out to be an important tool for the diagnosis of the conservation state of pigments.

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IMEKO-TC4-MetroArchaeo2022-040.pdf

DOI

10.21014/tc4-ARC-2022.040

IMEKO TC

TC4 - Measurement of Electrical Quantities

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