Very little is known about the driving forces behind the ageing processes in oil paintings: how fast they take place and how they are influenced by paint formulation, treatment and climate. This project aims to provide an improved scientific basis to guide conservation strategies.
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Disfiguring surface crusts, increased transparency and darkening, water sensitivity, crumbling of the paint, little globules of lead soaps that protrude through the paint surface: these are just some of the degradation phenomena encountered on the oil paintings selected for our research.
The conservation of most of these paintings, all from Dutch museum collections, is considered problematic. Although they vary in production methods and history, their degradation phenomena are representative of those commonly encountered in oil paintings. In all cases the degradation can be related to pigment-oil binder interactions, or lack thereof.
In the PAinT project four main scientific topics are defined that all play a role in the observed degradation phenomena.
Topic 1. Internal Paint Conditions
To understand the chemical and physical processes involved, more insight is needed into the internal conditions of the paint layers. We will focus on the relationship between the internal conditions and the pigment type.
Topic 2. Metal Soap Formation and Characteristics
Since many degradation phenomena are metal soap-related a separate study focuses on the circumstances and timescale for metal soap formation and the translation of the material properties of the pure metal soaps into their behavior in mature oil paint systems.
Topic 3. Migration and Transport of Mobile Paint Components
A third topic of research is the understanding of the migration and transport mechanisms of mobile paint components through the semi-permeable oil paint.
Topic 4. The Influence of External Factors
Finally, the influence of external factors (time, moisture, solvents, temperature and light) on the chemistry and physics of mature oil paint will be tested. A better understanding of the influence of these factors will help to evaluate the effects of past and present approaches to the conservation of paintings.
The research questions are addressed through a combined approach that links analyses of real paintings with scientific experiments on model systems. In our attempts to replicate mature oil paints for testing, the application of chemical synthesis methods and mathematical models is innovative in its approach. These models will be complemented with conventional approaches, where fresh, artificially and/or naturally aged paint reconstructions are employed. Synchrotron-based techniques as well as newly developed mass spectrometric and Raman techniques will be used to study paint cross-sections and oil paint dynamics in the various model set-ups. Of special note is the inclusion in the PAinT team of specialists in mathematical modeling of polymers (Piet Iedema), synthesis and characterization of metal soaps (Robert Corkery), and the development of advanced analytical and synchrotron-based techniques (Andrew Beale/ Bert Weckhuysen).