The enigma of Rembrandt’s vivid white #weekendusers

11-06-2018

Some of Rembrandt’s masterpieces are at the ESRF for some days, albeit only in minuscule form. The goal: to unveil the secrets of the artist’s white pigment.

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Seven medical students surround a dead body while they attentively look at how the doctor is dissecting the deceased. The scene is set in a dark and gloomy environment, where even the faces of the characters show a grey tinge. Strangely, the only light in the scene is that coming from their white collars and the white sheet that partially covers the body. The vivid white creates a perplexing light-reflecting effect. Welcome to painting The anatomy lesson of Dr. Nicolaes Tulp, a piece of art displaying the baffling technique of the impasto, of which Rembrandt, its author, was a master.

Impasto is thick paint laid on the canvas in an amount that makes it stand from the surface. The relief of impasto increases the perceptibility of the paint by increasing its light-reflecting textural properties. Scientists know that Rembrandt achieved the impasto effect by using materials traditionally available on the 17th century Dutch colour market, namely the lead white pigment (mix of hydrocerussite Pb3(CO3)2.(OH)2 and cerussite PbCO3), chalk (calcite CaCO3) and organic mediums (mainly linseed oil). The precise recipe he used is, however, still unknown.

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The team on ID13 (from left to right): Victor Gonzalez, Martin Rosenthal and Marine Cotte. Right picture: the setup on the beamline. 

“Our hypothesis is that the crystallite sizes and the crystalline composition in the different grades of white pigment can explain how the impasto is created”, explains Victor Gonzalez, researcher at TU Delft and the  Rijksmuseumin The Netherlands. “We also think that the interactions between mineral pigments and the organic binder can induce recrystallization processes within the lead white paint, and this could be responsible for the impasto effect”, he adds.

The team, also composed of scientists from the Center of Research And Restoration of the Museums of France (C2RMF), the Institut de Recherche de Chimie Paris (IRCP) in France and the Mauritshuis museum in The Netherlands has come to the ESRF’s beamlines to quantify the crystalline phases in Rembrandt’s impasto, to model the pigment crystallites morphology and size and to obtain crystalline phase distribution maps at the microscale.

The samples are less than 100 microns in size, so synchrotron radiation is the only way they can be studied. They will be analysed on ID22 and ID13. “We have successfully used ID22 in the past, so we know that it can provide high quality diffraction patterns”, explains Marine Cotte, scientist at the ESRF and also in the team. “On ID13 we will take advantage of the high speed of the Dectris EIGER detector to acquire X-ray diffraction maps over tens of thousands of pixels in few minutes”, she says.

Once they have the data analysis, they will compare Rembrandt’s recipes with other reconstructions of recipes used in Holland during the 17th century, to find out what he did differently from other contemporary artists. “Ultimately, our aim is to preserve this artwork for the long term”, Gonzalez concludes.

Top image: The anatomy lesson of Dr. Nicolaes Tulp, by Rembrandt.