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.

Stained-glass windows play an important role in cultural heritage. Human and environmental factors have subjected these pieces to risks of damage. Mechanical and chemical-based cleaning methods have been used for their restoration and conservation. Additionally, short-pulse lasers have opened new opportunities for safe and controlled cleaning and restoration of these important materials. In this work, ultra-short pulsed lasers were used to clean an artificially applied coating from the surface of a contemporary colorless glass frequently used in the restoration of stained-glass windows. One of the objectives was to explore the applicability of using these types of lasers to safely clean historical stained-glass windows. It was observed that temperature rise and subsequent heat accumulation in the coating layer being removed was sufficient to generate significant thermal stresses on the underlying glass surface leading to damages even when the laser energies are lower than the damage thresholds. Some laser treatments that limit this heat accumulation were designed in this study. For laser systems operating at frequencies in the range of several hundreds of kHz, the option was to work in burst mode, limiting the number of pulses in each burst and selecting an adequate time lapse between two consecutive burst runs. A method to uniformly clean a given surface is proposed in this work. When lower frequencies are available, treatments using frequencies lower than 20 kHz are enough to safely clean the glass. When UV laser radiation is used, optical damage is also an important aspect to be considered. In this case, the cleaning protocol has to deal with both issues, to avoid heat accumulation and chemical damage.