Scientists in the Netherlands have discovered changes in the chemical makeup of paint used in 17th-century masterpieces that signal supply chain disruptions, reports Mano Sundaresan for NPR.
In a study published earlier this month in Science Advances, researchers from Vrije University in Amsterdam analyzed 77 paintings created by 27 artists during the 17th century, or the so-called “Dutch Golden Age.” During this period, big name artists such as Frans Hals in Haarlem and Rembrandt van Rijn in Amsterdam produced art for patrons flush with cash from trade and colonial exploitation.
The Dutch masters shared a preference for “lead white,” a smooth paint made from a lead-based powder mixed with linseed oil or an equivalent binder, according to a Vrije statement. Artists would use the buttery paint to brighten and define their compositions, which often relied on dramatic contrasts between light and shadows, per NPR. As historic conflicts such as the English Civil Wars in 1642 and the Eighty Years’ Wars in 1568 disrupted the supply of lead from England to the Netherlands, Dutch artists were forced to adjust their recipes for lead white pigments. These changes, it turns out, significantly altered the chemical composition of the paint.
"We know that warfare was requiring a lot of lead. The civil war disrupted or changed the lead supply...and that's what we see in the pigments," lead study author Paolo D'Imporzano tells NPR.
Using a technique known as lead isotope analysis, D'Imporzano and his colleagues recorded the isotopic composition of white paint samples from each canvas, creating an international database. They found that lead white paints that were made from the same supply of lead ore—and sourced from the same geographic origin—bear similar chemical traces, notes the study.
With this data, researchers can compare the isotopic makeup of a work’s white paint to that of authenticated works—for instance, Rembrandt’s Tobit and Anna with the Kid, confidently dated to 1626—and determine when and where a particular canvas was produced.
As Sarah Wells reports for Inverse, scientists have used isotope analysis to date paintings for years. But the Vrije study stands out because it allows scientists to connect groups of paintings to specific historical events.
For example, the team found that a change in the chemical makeup of Dutch lead white paint corresponded to the years 1642 to 1647, or roughly the timeframe of the English Civil Wars, reports Brian P. Dunleavy of UPI. D’Imporzano tells Inverse that in the 17th century, Venice and the Netherlands were the main producers of the lead white pigment.
“And because the lead source used were different—Dutch producers were using British lead while Venice used different sources—the lead white made in these two places have a different, recognizable and characteristic isotopic signature,” explains D’Imporzano.
The team also discovered another cluster of outlying isotope compositions dated between 1648 and 1660, years that correspond to the Eighty Years’ War or the Dutch War of Independence, according to UPI.
Lead isotope analysis allowed the scientists to solve at least one art history puzzle, note the authors in the study. Scholars had long thought that Rembrandt's student Willem Drost painted his Roman-inspired work Cimon en Pero while working in Venice in the 1650s. Upon closer inspection, however, the painting's chemical signature bears a much stronger resemblance to that of paintings from Rembrandt's studio in Amsterdam—where Drost also worked for a time, D'Imporzano tells NPR.
D’Imporzano says he hopes that by studying the use of lead paints in Europe, experts can better understand who painted what, and where.
“In this way, we will be able to see to [what] extent [it] is possible to connect lead isotope ratios of lead white to individual painters, regions, time, and artistic groups,” he tells Inverse. “[A]nd how to use this data to provide useful information to the field of cultural heritage.”