Chemical Changes in Pictorial Models: Characterization by FT-IR Spectroscopy

Abstract

In order to understand the interaction between copper containing pigments and the organic binders in paintings, as well as reaction/alteration products, a series of pictorial models have been prepared and naturally aged. For this research, Fourier transform infrared spectroscopy (FT-IR) is used as the analytical technique, while it is useful in detecting functional groups, so it allows the identification of significant changes in the cured mechanism of the system prepared. For simulating the oil painting system, the methodology was based in thin-films so previously synthesized copper green pigments – identified as copper acetates, copper hydroxichlorides and mixtures of acetates and hydroxichlorides – have been mixed with the binding media (drying oils). These mixtures were layered on glass supports. By means of FT-IR measurements the oxidation is evident while a decrease in the hydrocarbon stretching and bending frequencies is observed (bands at 3000 - 2800 cm - 1). Another change in the models is the appearance of a shoulder in the region between 15 00 to 1600 cm - 1, which turns into a peak during the decay process.