In this study, the chemistry of air-drying artist’s oil paint curing and aging up to 24 months was studied. The objective is to improve our molecular understating of the processes that lead to the conversion of the fluid binder into a dry film and how this evolves with time, which is at the base of a better comprehension of degradation phenomena of oil paintings and relevant to the artists’ paint manufacturing industry. To this aim, a methodological approach based on thermogravimetric (TG) analysis, differential scanning calorimetry (DSC), gas chromatography–mass spectrometry (GC–MS), and analytical pyrolysis coupled with gas chromatography and mass spectrometry (Py–GC–MS) was implemented. Model paintings based on linseed oil and safflower oil (a drying and a semidrying oil, respectively) mixed with two historically relevant pigmentslead white (a through drier) and synthetic ultramarine blue (a pigment often encountered in degraded painting layers)were investigated. The oil curing under accelerated conditions (80 °C under air flow) was followed by isothermal TG analysis. The oxygen uptake profiles were fit by a semiempiric equation that allowed to study the kinetics of the oil oxidation and estimate oxidative degradation. The DSC signal due to hydroperoxide decomposition and radical recombination was used to monitor the radical activity over time and to evaluate the stability of peroxides formed in the paint layers. GC–MS was performed at 7 and 24 months of natural aging to investigate the noncovalently cross-linked fractions and Py–GC–MS to characterize the whole organic fraction of the model paintings, including the cross-linked network. We show that the oil–pigment combination may have a strong influence on the relative degree of oxidation of the films formed with respect to its degree of cross-linking, which may be correlated with the literature on the stability of painting layers. Undocumented pathways of oxidation are also highlighted.

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We present the results of a diagnostic campaign on three of Giuseppe Capogrossi’s abstract paintings from the 1950s and 1960s, conserved at the National Gallery of Modern and Contemporary Art in Rome. Non-invasive investigations by reflection FT-IR spectroscopy were carried out, followed by micro-destructive laboratory analyses using Py-GC-MS, and HPLC-ESI-Q-ToF. The investigations focused on identifying the binders used for both the preparation and the pictorial layers. In two of the paintings investigated, an industrial preparation was identified based on egg yolk, mixed with other organic materials (acryl resin, oil, animal glue). The paint media include the use of both oil and alkyd paint. In one of the three paintings, the presence of a styrene-acryl resin was observed. The results show the simultaneous use of traditional and innovative materials, confirming the complexity of the period in which the artist was active, characterized by the technical experimentation of both the artists and manufacturers. The research also contributes to a better understanding of Giuseppe Capogrossi’s artistic profile, from the point of view of executive techniques.

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