Brushing the starched, white collars of The Syndics into being, Rembrandt couldn’t have imagined that nearly 400 years later, this same pigment would be used to unravel political conflicts.
Hidden within this alabaster pigment favored by Dutch masters are lead isotopes that scientists can trace through chemical analysis to the original locations of their ore. Using this technique, a team of scientists studied 77 paintings covered in lead-spiked pigment. Their goal? To travel back in time to understand how the global trade of ore impacted the creation of art.
Paolo D' Imporzano is a research associate at the Vrije University Amsterdam and the first author of the new work. By tracing the supply chain related to this paint, D’Imporzano says that the team has uncovered unique insight into political disputes of the era, including the English Civil War and Anglo-Dutch-French conflicts.
“We identify a significant change in the lead isotopic composition of lead white in the period [of] 1642-1647,” D’Imporzano tells Inverse. “This change coincided with some important socio-economic events that, most probably, altered the supply chain of lead in the Netherlands, and therefore also affected the lead isotope ratios of lead white.”
The findings were published Wednesday in the journal Science Advances.
What’s new — Lead isotopes have been used to study cultural heritage since the 1960s, but what sets this study apart is how D’Imporzano and colleagues used this technique to connect the culture of Flemish painting to historical events. In particular, D’Imporzano says that previous analyses of this white lead paint helped himself and colleagues dig deeper into these paintings’ past.
“Several studies proved that it is possible to use lead isotope ratios of art objects to identify the provenance of the lead used in such objects,” D’Imporzano explains.
As for how this paint came to contain lead in the first place, D’Imporzano and colleagues explain in their paper that lead white — which is considered the “most important” of all white pigments — is a lead carbonate and the result of a chemical reaction. The result: a white powder that can be mixed with oil to create pigment.
“At the time, Venice and the Netherlands were the main producers of the pigment,” D’Imporzano says. “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.”
With these chemical differences in mind, D’Imporzano and colleagues were then able to compare the lead ratios of selected paintings to historical timelines and determine how they might’ve been the product of a robust or globally disrupted supply chain.
Why it matters — The use of naturalistic light and shadow is a cornerstone of what makes the Flemish art tradition so captivating even centuries after its creation. Learning more about the historical context of lead white — which the artists used to cast white light or lighten darker colors in these works — can help art historians better understand what drove this creative expression.
For example, did changes in the availability of lead white paint impact the color choices of these artists? Or, as the authors speculate, was this color choice important enough that artists brought their own white paints with them around the globe?
These are the kinds of questions that chemical analysis can hopefully start to answer.
How they did it — To make their analysis, the team looked at 77 paintings from 27 different artists created between 1588 and 1700. This included eleven paintings by Rembrandt.
Luckily, D’ Imporzano says the team didn’t have to take a scalpel to one of these masterpieces directly to extract a paint chunk. Instead, they used resin cast samples that had previously been removed from the artwork.
“This method allows sampling of individual paint layers of a cross-section between 10 and 50 micrometers in width,” explains D’ Imporzano. “In this way, no new samples were taken from paintings.”
These samples were then processed in a clean laboratory and analyzed using a kind of mass spectrometer that concentrates and analyzes ions to study samples’ isotope ratios. From this work, D’Imporzano says the team was able to draw some pretty clear conclusions.
“The first half of the 17th century is characterized by a stable lead isotopic composition,” he says. “The period 1642-1647 shows a transition that reached a new equilibrium in the period 1647-1680. The timing of the observed isotopic transition coincides with three major socio-economic events in Europe that would have had a major influence on the lead supply chain.”
In other words, during conflicts like the English Civil War, the English lead that Dutch painters relied on for their pigment was diverted toward ammunition. D’Imporzano and colleagues suggest that this would’ve led to the use of more local lead sources as well as the recycling of lead.
What’s next — This is only the beginning of what leaded paint can tell scientists about art and culture, D’Imporzano says. In the future, he plans to compare other lead-bearing pigments — like lead-tin yellow — to see whether they carry the same chemical tracking codes.
By studying the use of these leaded paints across Europe, D’Imporzano says he hopes to gain more insight into how artists’ experiences differed across the continent.
“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 says. “[A]nd how to use this data to provide useful information to the field of cultural heritage.”
Abstract: This study investigates how lead isotopes in lead white pigment can be used as an additional diagnostic tool to constrain the production time of 17th century Dutch paintings. Analysis of 77 well-dated paintings from 27 different Dutch artists reveal significant change in the source of lead used in lead white at the start, middle, and end of the 17th century. Isotopic shifts are related to major historical and socioeconomical events such as the English Civil War and Anglo-Dutch-French conflicts. These observations offer the prospect that lead isotope analysis of lead white could aid attribution and authentication of Dutch 17th century paintings and provide insights into artists’ international travels as well as lead production and trading.