Transport and behaviour of water in oil paintings

Preventive conservation of oil paintings is aimed at slowing down unwanted change by optimising the conditions in which the work of art is displayed or stored. To inform preventive conservation decisions, knowledge is necessary about the mechanisms responsible for detrimental chemical change in oil paintings, the rate at which change occurs and how change is influenced by the environment. Currently, only minimal quantitative data is available on the influence of the environment on chemical processes in oil paintings. To address this lack, this thesis investigates the relationship between humidity in the environment and the concentration and distribution of water inside oil paint. A computational approach is taken to calculate the transport of water through the different layers of an oil painting as a result of fluctuations in environmental humidity. The parameters for the diffusion model are estimated based on data from literature and water sorption experiments. The model is applied to gain a better understanding of the effect of wax-resin linings on the water transport behaviour of paintings. At the molecular level, the distribution of water in the oil paint polymer network is investigated using infrared spectrsoscopy and differential scanning calorimetry. Furthermore, a case study of water-based chemical deterioration in a 17th-century oil painting places this research in context of the complexity and material heterogeneity of historical paintings. In the last chapter, a suite of non-invasive imaging techniques is employed to monitor chemical and physical change in paintings, an essential step towards effective preventive conservation of oil paintings.