Model systems

A central problem in paint degradation research is that the underlying processes tend to take place over the course of months or even years. Obviously, that timescale is not very practical. Moreover, sample material from real paintings is always limited, and we have no control over the composition or history of a particular sample.

Microscopy image of a cross section of a paint sample under UV illumination.

To study exactly which chemical reactions cause an oil paint to change or degrade, or how fast degradation takes place, it is necessary to develop model materials. These materials should mimic the molecular structure of aged oil paint but react much faster,  while still being suitable for a particular kind detailed chemical analysis. This aspect of our research tends to be the most challenging bottleneck for progress.

Series of pigment samples that have partially degraded in a chemical reaction.

In our projects, we are constantly developing new model systems for oil paint. Examples include oil paints that contain metal ions but no pigment (1), oil paints where specific functional groups like esters or carboxylic acids have been removed or added (2), or oil paints that have been aged under varying humidity or temperature conditions. By careful experimental design, we are now starting to uncover the fundamental chemical pathways that can ultimately lead to severe paint degradation.