Enlarge / Composite image showing color variation of emerald green bookcloth on book spines, likely a result of air pollution (credit: Winterthur Library, Printed Book and Periodical Collection)

In April, the National Library of France removed four 19th century books, all published in Great Britain, from its shelves because the covers were likely laced with arsenic. The books have been placed in quarantine for further analysis to determine exactly how much arsenic is present. It's part of an ongoing global effort to test cloth-bound books from the 19th and early 20th centuries because of the common practice of using toxic dyes during that period.

Chemists from Lipscomb University in Nashville, Tennessee, have also been studying Victorian books from that university's library collection in order to identify and quantify levels of poisonous substances in the covers. They reported their initial findings this week at a meeting of the American Chemical Society in Denver. Using a combination of spectroscopic techniques, they found that several books had lead concentrations more than twice the limit imposed by the US Centers for Disease Control (CDC).

The Lipscomb effort was inspired by the University of Delaware's Poison Book Project, established in 2019 as an interdisciplinary crowdsourced collaboration between university scientists and the Winterthur Museum, Garden, and Library. The initial objective was to analyze all the Victorian-era books in the Winterthur circulating and rare books collection for the presence of an arsenic compound called cooper acetoarsenite, an emerald green pigment that was very popular at the time to dye wallpaper, clothing, and cloth book covers. Book covers dyed with chrome yellow—favored by Vincent van Gogh—aka lead chromate, were also examined, and the project's scope has since expanded worldwide.

Enlarge / Rembrandt's The Night Watch underwent many chemical and mechanical alterations over the last 400 years. (credit: Public domain)

Since 2019, researchers have been analyzing the chemical composition of the materials used to create Rembrandt's masterpiece, The Night Watch, as part of the Rijksmuseum's ongoing Operation Night Watch, devoted to its long-term preservation. Chemists at the Rijksmuseum and the University of Amsterdam have now detected unusual arsenic-based yellow and orange/red pigments used to paint the duff coat of one of the central figures in the painting, according to a recent paper in the journal Heritage Science. It's a new addition to Rembrandt's known pigment palette that further adds to our growing body of knowledge about the materials he used.

As previously reported, past analyses of Rembrandt's paintings identified many pigments the Dutch master used in his work, including lead white, multiple ochres, bone black, vermilion, madder lake, azurite, ultramarine, yellow lake, and lead-tin yellow, among others. The artist rarely used pure blue or green pigments, with Belshazzar's Feast being a notable exception. (The Rembrandt Database is the best resource for a comprehensive chronicling of the many different investigative reports.)

Early last year, the researchers at Operation Night Watch found rare traces of a compound called lead formate in the painting—surprising in itself, but the team also identified those formates in areas where there was no lead pigment, white or yellow. It's possible that lead formates disappear fairly quickly, which could explain why they have not been detected in paintings by the Dutch Masters until now. But if that is the case, why didn't the lead formate disappear in The Night Watch? And where did it come from in the first place?