When Karen Wen told her family and friends she was spending her summer hunting for poison books within Western Libraries, they were shocked.
“You’re touching poison?” they asked Wen, whose work involved no risk of harm.
Wen laughs now but appreciates their initial concern. She had a similar reaction when first encountering a potential toxin while visiting Western’s Archives and Research Collections Centre (ARCC) in professor Kyle Gervais’ medieval manuscript class.
Noticing a vibrant white pigment on one letter of the text, she wondered if it was lead. When special collections librarian Deborah Meert-Williston confirmed the possibility, Wen was stunned.
Karen Wen
“It was jarring to see a potentially poisonous material right in front of me,” she said.
Her fear shifted to fascination as Meert-Williston discussed the likelihood of poisonous pigments not only in medieval manuscripts, but in books from the Victorian era as well. Specifically, those bound in emerald green cloth, dyed with a copper-arsenic compound, which are known today as ‘poison books.’
Wen was further intrigued after Meert-Williston directed her to the Winterthur Poison Book Project, an initiative housed at the University of Delaware, in Newark, Delaware.
The project, which began in 2019, focuses on identifying, handling and storing potentially toxic collections and building the body of knowledge of 19th century bookbinding.
The initiative also inspired an undergraduate summer research internship for Wen, a third-year English major in the School for Advanced Studies in the Arts and Humanities (SASAH). She spent several months tracking down potentially poisonous books at Western, using the Poison Book Project as a guide.
Under the supervision of English and writing studies professor M.J. Kidnie and mentorship of Meert-Williston, Wen visually analyzed more than 7,000 books as part of her search. Through a humanities research lens, she explored the social impact and materiality of poison books. Her work also considered the tension between preservation, access and contemporary handling of poison books within libraries and archives.
She identified 96 books containing potentially toxic pigments while gaining practical research skills and a new appreciation for the differing cultural and social attitudes towards arsenic throughout history.
What are poison books?
Poison books are bound with components containing emerald green (copper acetoarsenite) or Scheele’s green (copper arsenite). These books were published mostly in the 19th century.
“For readers of that era, the brilliant green colour was appealing, not only as a beautiful shade to display on the bookshelf but also as a tasteful gift, especially perhaps for women, given the fashion and aesthetic trends of the time,” Wen said.
Arsenic, notorious throughout history as a highly effective and hard-to-detect poison, was also used widely in everyday items of the time period, from soap to medicine. Beyond books, its green hue illuminated wallpaper, clothing, cosmetics and toys.
It’s believed this widespread use meant readers of that time –although aware of arsenic’s toxicity – didn’t view it strictly as a poison or with the same caution we exercise today.
Wen said understanding this important cultural and societal distinction helped her try to apply an unbiased approach to her work.
“Today, when people hear the word ‘poison,’ they immediately think of lethal danger, but what exactly does poison mean? Arsenic was used to intentionally kill people, but also in medical or beauty treatments, for example, to remove body hair.
“Just because it’s poisonous doesn’t mean that it’s evil.”
“The goal of my research was not to elicit a complete or generalized distrust of arsenic. When encountering something labeled as poisonous, we should think critically about the context of its use, misuse and abuse, and consider how substances acquire their meanings through time and practice.”- Karen Wen, third-year English student and 2025 undergraduate summer research intern
Searching for poison books: A multi-pronged process
To conduct her search, Wen began by matching titles with those in the Winterthur Poison Book Project database. She then visually scanned the library stacks using the Poison Book Project’s swatch bookmark, a tool that helped her compare any green 19th-century books to shades known to be hazardous.
One title, The Paragreens on a Visit to the Paris Universal Exhibition by Giovanni Ruffini and John Leech, which Wen identified using the Winterthur database, was tested using X-ray fluorescence (XRF) spectroscopy in Western’s Earth and Planetary Materials Analysis (EPMA) Laboratory with the support of archaeology and biological anthropology professor Andrew Nelson. Results confirmed the book contained both copper and arsenic.
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- A swatch bookmark from the Winterthur Poison Books Project at the University of Delaware helped undergraduate summer research intern Karen Wen identify poison books at Western Libraries. (Submitted)
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- “The Paragreens on a Visit to the Paris Universal Exhibition” by Giovanni Ruffini and John Leech, identified as a poison book at Western Libraries, was tested using X-ray fluorescence (XRF) spectroscopy at Western’s Earth and Planetary Materials Analysis (EPMA) Laboratory. (Submitted)
More than 90 potential poison books and counting
Although Wen identified close to 100 potentially poisonous books throughout her internship, she expected she’d find more.
“It’s a bit of a double-edged sword,” she said. “Perhaps it’s positive from a public safety perspective, but there’s a lot to learn from these books from a historical and material culture perspective.”
Wen said many volumes in circulation may have been rebound over the years.
“People didn’t know what they were fixing,” she said, adding that when the physical book is destroyed, so too is its social and historical context. “We lose what was embedded in its materiality – how it was produced, circulated and understood.”
Protocols for poison books
Experts working on the Winterthur Poison Book Project maintain that as long as the pigments aren’t ingested (warning, ‘don’t lick the books!’) these books don’t pose any significant risk to the public. Still, they’ve developed safety precautions, especially for those who handle the books more frequently.
“As we continue to identify these books, we put them in bags with labels informing users the bindings may contain arsenic and that they should wash their hands after use,” Meert-Williston said. “Most books are available digitally, so if they choose not to handle the book, they can still access the content.”
While Wen’s search was extensive, many books in Western’s collection remain unexamined. It is a labour-intensive job requiring time, knowledge and physical stamina to access books often on high or low shelves.
Her biggest learning?
“To not judge a book by its cover,” she said. “It sounds counterintuitive, because I was literally judging these books by their covers. But in a metaphorical sense, there are so many more layers – culturally, literally, textually, symbolically – to this work that we can explore and research with more depth.”
