Rembrandt put lead in the oil of his canvases

This is a first in the history of the scientific study of paintings. An international team revealed lead formates in the oil of an old painting. And not just any: Victor Gonzalez, postdoctoral fellow at the Supramolecular and Macromolecular Photophysics and Photochemistry Laboratory (CNRS, ENS Paris-Saclay) and his colleagues detected this compound in The Night Watchthe emblematic work painted by Rembrandt (1606-1669) in 1642. This discovery, published in the German journal Angewandte Chemie on January 2, intervenes within the framework of the vast project of research and restoration of the masterpiece baptized ” Operation “Night Watch” »launched by the Rijksmuseum in Amsterdam (Netherlands) in 2019.

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As often, the discovery is the result of technological progress… and chance. The team had just received a new type of scanner by X-ray diffraction. Passing it in front of the painting, the device should make it possible to know not only the elementary chemical elements present in different parts of the canvas, but also their crystalline structure. “Obviously we were interested in pigments known to be rich in leadsays the French researcher. And there, surprise: not only do we discover lead formates, but we identify them in areas where there is no lead pigment, white, yellow…” The researchers then transmitted microsamples of paint to the European synchrotron in Grenoble (ESRF). And the supermicroscope confirmed the verdict.

Stages of identification of lead formates (right image) in the oil of

The presence of lead formats alone is intriguing. These compounds have never been identified on the palette of the Dutch genius. Nor do they exist in the atmosphere. They are therefore the products of an in situ reaction. But which and where? For lack of recipes left by the painter, it was first necessary to speculate. “It didn’t seem to be related to the pigment, I thought it could be the oil, even though I was not aware of any identification of dried oil in paintings from this period”continues Victor Gonzalez.

Accelerate the drying of canvases

It was in the laboratory that the researchers verified the hypothesis. By mixing formic acid and lead oxide and introducing this mixture into heated linseed oil, they were able to confirm the rapid appearance of lead formates in the paint layer. A recipe probably designed by the great Dutch innovator to speed up the drying of his canvases.

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