Rocketeers in de regen

Studenten van het Dawn-project van het dreamteam Dare (Delft Aerospace Rocket Engineering) testen verschillende concepten van de ontsteking voor de nieuwe hybride raketmotor, die moet concurreren met de vaste stuwstof voortstuwing zoals die tot nu toe werd toegepast in de Stratos II raket van Dare.

The scientists, among them paint expert, Professor Joris Dik (faculty MMME), took samples of yellow paint that had turned brown from the paintings ‘View of Arles with Irises’ (1888) and ‘Bank of the Seine’ (1887), both on display in the Van Gogh Museum in Amsterdam. Through X-ray analysis they discovered that the darkening of the top layer was caused by a reduction of the chromium in the chrome yellow (from Cr(VI) to Cr(III)). Prof. Dik and his colleagues published the results this week online in the journal Analytical Chemistry.
The research, led by Koen Janssens of Antwerp University, was further conducted by an international team of scientists from four countries. The scientists deployed an impressive arsenal of analytical tools, with synchrotron X-rays at the European Synchrotron Radiation Facility (ESRF) in Grenoble (France) providing the final answers. “I am not aware of a similarly big effort ever having been made for the chemistry of an oil painting,” said Prof. Dik in an ESRF press release.

According to the professor, the faded paint also contained lots of barium and sulphur. “These atoms probably originate from barium sulphate, a colourless filling material that was added to the paint. This filling might be the cause of the change in colour.”

The researchers also collected samples from three left-over historic paint tubes. After these samples had been artificially aged for 500 hours using an UV-lamp, only one sample, from a paint tube belonging to the Flemish Fauvist Rik Wouters (1882-1913), showed significant darkening. Within three weeks its surface of originally bright yellow had become chocolate brown. This sample was taken as the best candidate for having undergone the fatal chemical reaction, and X-ray analysis identified the darkening of the top layer as linked to a reduction of the chromium.

This is not the first time Prof. Dik and his colleagues have made headlines with their research on paintings. In 2008, using X-ray techniques as well, they discovered an early rejected painting of a face of a woman underneath Van Gogh’s ‘Patch of Grass’ painting.

Begin mei moet de grote lanceercampagne plaatsvinden. 



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