Rembrandt used a lead-containing layer for the Night Watch

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Rembrandt protected the canvas of The Night Watch with a lead-containing layer. It was the first time he used this technique, probably to protect the canvas against moisture. This layer, which is still beneath the primer layer, was discovered thanks to a 3D research technique that has not previously been applied to samples of historical paintings. The new insight helps with the conservation of the painting.

Researchers from the Rijksmuseum, the University of Amsterdam, Utrecht University and the University of Antwerp who collaborate in the Netherlands Institute for Conservation Art Science write about it on Friday in the scientific journal Science Advances. The work is part of Operation Night Watch, an extensive research and renovation project that started in 2019.

Most of Operation Night Watch took place by minutely examining the surface of the painting with X-ray scanners. This already made it clear that a lot of lead was used in The Night Watch, including in the light yellow paint of Lieutenant Van Ruytenburgh’s costume. These scans also showed streaks glowing across the entire painting, which are clearly visible in the dark parts.

Previous research, in 1975, showed that Rembrandt used a different type of primer for The Night Watch than he applied in earlier work, consisting of quartz clay. But this did not explain the presence of so much lead all over the canvas.

For this additional research, focused entirely on the underlying layers, a sample was cut from the painting. A sliver of 55 micrometers thick and 160 micrometers long. The researchers took it to Hamburg, Germany, where there is a synchrotron, a type of particle accelerator that can be used to perform micro-X-ray fluorescence and ptychography. They irradiated the sample with X-rays and the composition of the sample can be deduced from the reflection of the radiation. By rotating the sample ever so slightly, a 3D image is ultimately created.

“What we saw really surprised us,” says chemist Fréderique Broers of the Rijksmuseum, first author of the study. “The distribution of the lead particles was so concentrated at the bottom of the sample that it had to come from a specific lead-containing layer.”

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<strong>Katrien Keune:</strong> “As a twelve-year-old, I was fascinated by materials.”” class=”dmt-article-suggestion__image” src=”https://images.nrc.nl/FlZb8ukqJVcdHve41yFlisKEqQw=/160×96/smart/filters:no_upscale()/s3/static.nrc.nl/images/gn4/stripped/data85435279-e64fa4.jpg”/></p><p>However, the lead-containing layer itself was not visible, and the sample taken did not appear to contain all layers. “That is why we also looked at another sample, which was picked up after the knife attack on De Nachtwacht in 1975. The attacker then stabbed all the way through the cloth,” says Broers. “We did find the lead-containing layer in that part.”</p><p>Preparation of the canvas, before applying a base coat, was also very common in Rembrandt’s time. “It ensures that oil from the paint is not immediately absorbed by the canvas,” says Broers. “Normally this was done with some kind of glue. But we couldn’t detect any adhesive layer.”</p><p>Rembrandt probably chose the new material because it would be better moisture-resistant, the researchers think. The Night Watch was made to be hung in the main hall of the Kloveniersdoelen in Amsterdam, on a long outside wall overlooking the windows. A relatively damp place. The method was not widely used, but the researchers found a clue to the use of a lead-based impregnation layer in a book on painting techniques written by Théodore de Mayerne during Rembrandt’s time.</p><p>“A note about this is in the margin of the book,” says Broers. “De Mayerne writes about a painting that was hung against an outside wall and in which the paint came loose due to moisture. He writes that in such situations a leaded oil may work better. It looks like Rembrandt could have known about this. It is striking that he used a new technique for both the impregnation layer and the primer layer for this important canvas.”</p><p>Was it a good choice by Rembrandt? Lead is very reactive. Lead particles easily end up in other layers. And one of the big problems for De Nachtwacht is the development of ‘lead soaps’, a kind of lead pimples that break through the paint as white dots.</p><p>“I don’t think Rembrandt could have foreseen what the choice for a lead layer would result in almost 400 years later,” says Broers. “But if he had used his standard primer, white lead instead of quartz clay, lead molecules would also have migrated through the painting. Moreover, the painting has been treated for restoration very often. The back has been treated with beeswax, among other things. The heat required for this may well have intensified the chemical reactions that led to the lead soaps. The fact that we now know that it contains a lead-containing layer is therefore valuable for future conservation work.”</p><p><dmt-util-bar article=

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