A new study describes the unexpected discovery of a lead compound in Rembrandt’s ‘The Night Watch’, raising questions about the compound’s origins.
Researchers have discovered an unusual lead compound called lead formate in Rembrandt’s masterpiece ‘The Night Watch’. Described in a study published in the journal ‘Angewandte Chemie International Edition’, this unprecedented discovery offers new clues on the painting’s history and its conservation state.
Largely considered Rembrandt’s most famous work, ‘The Night Watch’ was completed in 1642 and is the largest surviving work of art he ever created. Today it is displayed in Amsterdam’s Rijksmuseum. In 2019, an international research team joined forces in Operation Night Watch, the largest research and conservation project ever undertaken for this masterpiece. Supported by the EU-funded projects ParisRegionFP, InnovaXN, STREAMLINE and CALIPSOplus, the team sought answers on how the artist painted ‘The Night Watch’, the painting’s current condition and how it could be best preserved for future generations.Using X-ray powder diffraction and infrared microscopy, the team was able to identify lead formate in several areas of the painting. This is the first time that this compound has been detected in historical oil paints. “In paintings, lead formates have only been reported once in 2020, but in model paintings (mock-up, fresh paints). And there, surprise: not only do we discover lead formates, but we identify them in areas where there is no lead pigment, white, yellow,” comments the study’s first author Dr Victor Gonzalez of CALIPSOplus project partner French National Centre for Scientific Research (CNRS) in a news item posted on ‘ScienceDaily’. “We think that probably they disappear fast, this is why they were not detected in old master paintings until now,” the CNRS researcher explains.
So, did Rembrandt use lead-based oil paint? According to Rijksmuseum’s head of science and study senior author Prof. Katrien Keune, the presence of lead formate in the painting provides valuable insight on this, as well as on “the potential impact of oil-based varnishes from past conservation treatments, and the complex chemistry of historic oil paintings.”
To find out more about the lead compound’s origin, Rembrandt’s workshop recipes and the chemical mechanisms active in the layers of old paint, the team analysed fragments taken from the masterpiece as well as model samples simulating the painter’s formulations. To prepare the model samples, they hypothesised that Rembrandt used an organic binder (linseed oil) containing lead oxide, an alkaline lead compound often used by 17th-century Dutch artists as an oil drying agent.
Study co-author Dr Marine Cotte, a scientist at InnovaXN and STREAMLINE project coordinator and CALIPSOplus project partner European Synchrotron Radiation Facility (ESRF), France, states: “Thanks to the unique analytical performance of the ESRF, the world’s brightest synchrotron light source, we could map the presence of formates at a micrometric scale, and follow their formation over time.” The observations made enabled the scientists to form new hypotheses about the chemical conditions of the compounds’ in situ crystallisation in old paint layers.
Next, the team aims to study the origin of these formates to determine if they might have originated from past restoration treatments. The ParisRegionFP (Paris Region Fellowship Programme) project ends in 2025. InnovaXN (Doctoral programme for innovators with X-rays and neutrons) and STREAMLINE (Sustainable research at micro and nano X-ray beamlines) end in 2024. CALIPSOplus (Convenient Access to Light Sources Open to Innovation, Science and to the World) ended in 2021.
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