Joen Hermans

After our previous work gave us the methods to monitor metal soap crystallization kinetics, a new paper in Phys. Chem. Chem. Phys. now shows that water catalyzes the zinc soap crystallization process. We could also demonstrate that polar organic solvents that contain water impurities have an enormous effect on zinc soap crystallization by delivering water quickly deep into paint layers. These result are very important for paintings conservation, where such solvents are frequently used during conservation treatments.

A new paper is out this week in Phys. Chem. Chem. Phys. Building on our previous work to resolve the structures of metal carboxylates in oil paint, we were now able to study the kinetics of metal soap crystallization in great detail. With this fundamental work, we are starting to understand why zinc and lead soaps behave so differently in paintings. Moreover, we may be able to use the structure of metal soaps as a marker for the conservation history of paintings and the internal chemical conditions of paint layers.

Focus is a nightly radio show on NPO-Radio1 all about science and research. I had the pleasure of talking to host Jacob de Vries for an hour about paintings, oil molecules, changing pigments and beautiful music. You can find the interview here, or listen to it as a podcast on your favourite music player here.

In our new paper in ACS Applied Polymer Materials, we applied our recent insights into the molecular structures of zinc carboxylates to follow the evolution of zinc carboxylates in oil paint polymers. Using ATR-FTIR spectroscopy and constrained peak fitting algorithms, it was possible to accurately track structural changes during paint drying and ageing. Interestingly, it turns out that the zinc carboxylates can be used as markers for the local chemical conditions inside oil polymer networks.

In November 2019, I gave an interview about oil paintings and research for the podcast of Folia, the independent news outlet of the University of Amsterdam. If you want to hear more about the changes in paintings and the research we do to help preserve artworks, you can listen to the podcast on Spotify, iTunes or Soundcloud (in Dutch).

We published a nice paper in the journal Science Advances, where we used 2D-IR spectroscopy to elucidate the molecular structure of zinc carboxylates in oil paint films that contain the pigment zinc white. This research has solved the long-standing question about the origins of the broad carboxylate band in IR spectra of zinc white paint films. With this work, we are learning a lot about the inherent reactivity of zinc white paint layers, and the potential effects of water exposure/humidity on oil paint chemistry.

The popular science magazine ‘New Scientist’ awards a prize for the most promising Dutch or Flemish researcher. This year, I am one of the nominees! The finalists are selected by a combination of a jury and a public vote. Please vote before May 6th! Link to voting page (in Dutch) here

On October 8th, I gave a lecture at the Koninklijke Maatschappij voor Natuurkunde o.d.z. Diligentia (Royal Society for Natural Science) in The Hague. Having attended many Diligentia science lectures as a high school student, I felt honoured to be invited to bring my own research on stage eleven years after graduation. It was a privilege to share some of the progress we have made in the study of oil paint chemistry with such an enthusiastic audience. The lecture (Dutch) is available online on YouTube .

More information: natuurwetenschappen-diligentia.nl (Dutch)

We recently published a paper in Macromolecules that discusses methods to quantify the swelling and diffusion processes that occur when oil paint films are exposed to solvents. Using time-dependent ATR-FTIR spectroscopic data, we developed a mathematical model that describes the spread of solvent through a paint film. While it proved difficult to predict diffusion rates based on solvent properties, strong swelling and fast diffusion seem to go hand in hand.