Rembrandt covered the canvas of his largest and most famous work, popularly known as The Night Watch, with a layer of lead-rich oil paint in order to protect it from humidity, according to a study published this Friday in the journal Science Advances. It is the latest discovery of Operation Night Watch, a project that since 2019 has sought to know every detail of the painting, as well as the techniques, styles and pigments used by the painter. The final objective is to find the best strategy that guarantees its conservation.
The lead was causing the researchers to lose their minds. Some light pigments, such as certain yellows and whites, contain this element which, over time, tends to gather into small protuberances that deform the paintings. However, in Rembrandt's masterpiece, these bubbles are everywhere, also in unexpected areas.
To investigate its origin, the international team of scientists who carried out the work analyzed a piece of paint thinner than a human hair in the light of a synchrotron. These particle accelerators can produce X-rays so concentrated that they allow analysis on a microscopic scale. The result is a kind of photo of the sample in which each chemical component present in it is highlighted.
The researchers exposed the fragment of the work to this beam of light and took measurements with two different detectors, one that allows us to know the chemical elements present (titanium, lead, iron, strontium and calcium), and another that analyzes the oil and the particles. of quartz.
“After doing a scan, we rotate the sample one degree and repeat the process, and so on throughout 360 degrees,” explains Fréderique Broers, researcher at the University of Amsterdam and first author of the article, in an email to La Vanguardia. In total, each detector provides 360 images, one for each angle, which, combined, allow a 3D reconstruction of how the paint ingredients are distributed.
This three-dimensional vision, never seen before (at least with this level of detail), “provides a lot of information about the composition of the paint, and the shape and sizes of the particles of each pigment,” says the expert. And in this 3D replica, the researchers identified that in the deepest layers of the work, there was a large amount of lead that they did not expect.
“Then we scanned the entire Night Watch, and we saw that lead is present on the entire surface of the paint, even in dark areas. This suggests the use of a coating impregnated with a lead-containing product throughout the entire paint. Furthermore, a second fragment of paint collected from the ground after the knife attack on the painting in 1975 shows, under the microscope, this layer that contains lead,” summarizes the expert.
“We also have a historical source [a 17th-century manuscript] that suggests using a layer of oil impregnation containing lead instead of a layer of adhesive [the usual practice] if you have a painting that will be hung on an exterior wall.” , he continues, as was the case with Rembrandt's work. The evidence left no doubt: the painter used an unusual technique to protect his largest painting from humidity.
The researchers trust that the discovery will contribute to improving the conservation capacity of the work and see their results as another step towards completing the Operation Night Watch project. “We are in the final phase of the research, looking at whether and how we can remove the varnish safely,” something necessary from time to time to keep the paint in good condition.
Achieving this will be a key step to guarantee the quality of a work that, with its 400 years of history, requires careful conservation in order to continue providing enjoyment to visitors to the Rijksmuseum in Amsterdam.
