Unidentified lead layer found in Rembrandt39s The Night Watch

Unidentified lead layer found in Rembrandt's The Night Watch

Rembrandt, the Dutch Golden Age master, used lead in a waterproofing layer under the background to prepare his most famous painting, The Night Watch. It is the first time that this type of coating has been observed on the entire surface of the work. This was possible thanks to an advanced combination of X-ray and 3D imaging techniques, which allowed us to observe both the painting's pigments and binder. Because lead creates tiny dents that can fall off and damage paint, preservation treatments can be refined in the future. The discovery came during the research process called Operation Night Watch, which has been carried out since 2019 by the Rijksmuseum in Amsterdam, where the painting is exhibited. The scientists tasked with the work believe that Rembrandt wanted to protect it from moisture as it hung on a damp wall in the headquarters of a civil guard in the Dutch capital, which commissioned it in 1639.

The research was published this Friday in the American journal Science Advances and goes beyond the non-invasive observations that have so far been carried out in the museum itself, largely in public. This time the aim was to obtain more information about the morphology of a sample, and this involved extracting a tiny color fragment. To identify the chemical elements of the lower layers, the small part was placed in front of the synchrotron's X-ray beam. [acelerador de partículas]. The sample was then scanned with X-rays using two detectors to measure their interaction. According to Fréderique Broers, scientific researcher at the Rijksmuseum and lead author of the work, “One of the detectors is X-ray fluorescence to measure the different energy emitted by the elements of the fragment.” “The other detector is a pictogram [que busca cambios en la región superpuesta] and looked at the inflection [desviación] of X-rays.” In a telephone conversation he goes on to say that after scanning the fragment once, “we rotate the fragment by one degree and repeat the scan through 360 degrees.” “In this way we obtained 360 2D images [dos dimensiones] with which we reconstructed its volume in 3D.”

White lead was one of the most popular pigments of the 17th century among painters, and crystallized lead globules had already appeared in the areas of the Night Watch where the artist made these brushstrokes. For example in some items of clothing. The surprise was to find a lot of lead throughout the painting, including in the dark areas. “These protuberances can come loose and small holes appear in some parts of the painting due to the fall,” says Broers. Although it is a phenomenon difficult to reverse, he emphasizes that for now it does not affect the viewer's vision, “and these studies can help improve preservation and cleaning, since lead can migrate through the fabric before it crystallizes .” “When they become such pimples, they stay in place or fall off.” The occurrence of this phenomenon is not new. At the end of the 1990s, something similar was first discovered in another work by the painter, “Dr. Tulp’s Anatomy Lesson,” which was exhibited at the Mauritshuis Gallery in The Hague. The discovery of the lead layer in The Night Watch using 3D technology explains how these spheres were formed in the dark part.

Graphic describing the X-ray fluorescence scan in the dark areas of The Night Watch, where the lead-containing brush strokes found during the examination can be seen.Graphic describing the X-ray fluorescence scan in the dark areas of The Night Watch, where the lead-containing brush strokes found during the examination can be seen. Fréderique Broers/Rijksmuseum

This way of preparing the canvas shows how modern Rembrandt was for his time. Golden Age painters had a wide range of products at their disposal to create their mixtures and achieve the desired tones, and Rembrandt knew that The Night Watch should hang on a wall overlooking the street on the other side. It was a wet surface for which prior protection with a more traditional adhesive was not sufficient. There is a historical source that mentions the possibility of paint separating from fabric when wet and suggests the use of leaded oil instead of other binders. “It is a manuscript written by Théodore de Mayerne between 1620 and 1646, a kind of guide in which this technique is mentioned and we believe that Rembrandt knew it,” says Broers. Although the book was very popular at the time, they are unsure if other artists exploited lead in this way. “The use in wood to control humidity has been proven.” De Mayerne, a Swiss-born doctor and chemist, based his work on conversations with painters and is considered one of the first proponents of art conservation.

You can buy the canvases with the ideal preparatory layer in order to then apply the paint that is already included, or entrust this task to painters' assistants and students. Was it toxic to work with lead in this way? “It’s not just the leadership. The yellow color may contain arsenic or other things. Like smalt blue [esmalte]“This was a type of ground glass that contained cobalt and allowed for a thick texture,” says the researcher. The danger, he says, “is in the production of the mixtures because the dust particles can be inhaled, but the pigments were only put into paint tubes with the chemical revolution of 1841.” Apart from the artists' taste preferences and a certain secrecy about their palette There were also manuals for genres such as flower and fruit still lifes. One of its authors was the Dutch painter Willem Beurs, who in 1692 signed the first written source on oil painting “with instructions on how to apply the necessary layers for a convincing effect,” the researcher remembers.

The Night Watch is actually titled “The Military Company of Captain Frans Banninck Cocq and Lieutenant Willem van Ruytenburgh”. Frans Banninck Cocq asked Rembrandt to immortalize her along with the 17 members of his militia. It is a large painting (359 x 438 centimeters) that was exhibited for the first time in one of the rooms in the building used by the Citizen Guard itself. They called themselves Kloveniersdoelen, where they met and trained. Completed in 1642, it was not a night scene. It got its name because of the color that the paint took on over time. The painting was moved to the town hall in central Amsterdam around 1715. Since 1885, it has been the star of the Rijksmuseum's collection, which plans to announce the next step of Operation Rembrandt in a few months.

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