Works by Rembrandt (1606-1669) are often easy to spot. Trained completely in the North – unusual for the time, artists often worked towards studying in Italy – Rembrandt built a career and name for himself. As one of the most well-known Dutch artists, he is often thought of as a painter of light and shade expertly contrasting the two. His knack for realism and skilled impasto techniques give a life-life element to his paintings. This week, though, Angewandte Chemie, a German scientific journal, published a study shedding light on the secret of how, exactly, Rembrandt may have been able to finesse his use of impasto.
Using a number of cutting-edge tools, including imaging techniques, researchers were able to find the exact combination of ingredients used to create Rembrandt’s famed impasto. The Old Master’s personal concoction used traditional 17th century materials like lead white pigment, cerussite, and linseed oil but scientists also found an ingredient that, until now, was missing from our understanding of the artist: plumbonacrite. Yes, to those of you familiar with car manufacturing and painting, it’s the same colour preservative used in making red and orange paints for vehicles today.
The mineral is an extremely rare find in paintings of any era but specifically for the 17th century. Until now, the compound was only occasionally found in the works from the 20th century and once in a 19th century painting by Dutch master Vincent van Gogh. ‘We didn’t expect to find [plumbonacrite] at all, as it is so unusual in Old Masters paintings,’ said Dr. Victor Gonzalez, of the Rembrandt Rijksmuseum in Amsterdam and Delft University of Technology. Dr. Gonzalez, who was the study’s main author continued: ‘What’s more, our research shows its presence is not accidental or due to contamination, but the result of an intended synthesis.’
Literally translating to mean ‘to put in paste,’ impasto is a technique used by artists creating thick layers of paint that often projects out from the canvas showing brush and knife strokes while creating a textured surface. More surface area also meant for more light-reflection lending itself to more interesting colours.
Using scanning machines from the European Synchrotron (ESRF) in France, researchers were able to understand Rembrandt’s impasto better. Removing a sample less than 0.1mm in size, three paintings – The Portrait of Marten Soolmans (1634), Susanna (1636), and Bathsheba (1654) – researchers were able to use radiation x-rays to figure out the chemical combination of the samples. Dr. Marine Cotte, an internationally known art conservation expert at the ESRF, said of their findings ‘[t]he presence of plumbonacrite is indicative of an alkaline medium […] Based on historical texts, we believe that Rembrandt added lead oxide, or litharge, to the oil in this purpose, turning the mixture into a paste-like paint.’
Though the study found the compound in all three of the samples, it is not known if plumbonacrite was used systematically in lead white impastos. The findings do, however, change the game for conserving Rembrandt’s paintings for future generations since more is known, now, about the potential chemical makeup of Rembrandt’s works.