Tedone and Grayburn developed a protocol for testing other green books in the Winterthur library and created the Poison Book Project to document their progress. To date, they have tested approximately 350 green books from Winterthur’s collection, about 10% of which contained arsenic. Other institutions are adding their positive arsenical books to the database as well.

Identifying a “poison book” is a four-step process, Grayburn explained, beginning with visual identification. The green hue is so distinctive that simply looking at the book cover can determine which books should be tested further.

Next, conservationists use two standard technologies to identify chemical compounds: X-ray fluorescence and Raman spectroscopy. The first, commonly called XRF, identifies elements present in an object, such as arsenic and copper. These tests can be done easily with a hand-held tool that is as simple as using a bar scanner.

If the suspected elements are found, Raman spectroscopy provides in-depth analysis that identifies specific pigments, such as emerald green. Spectrometers are larger, non-portable machines, making them less common.

As non-destructive tools that leave the books intact, Raman and XRF are preferred methods for conservationists. The fourth step of sending samples to the Soil Lab is used very rarely, as it cannot be done without destroying the sample.

Ortegon’s experience inspired their personal research interest in the pigment vermillion, which contains mercury sulfide, and their knowledge of the analytic techniques helped Ortegon land a two-year residency with Northwestern University that begins this fall, where they will be part of analyzing 2,000 books from the university collection to identify and catalog toxic substances like emerald green, chrome yellow and vermillion.

The Poison Book Project

In contrast to the manufacturers who kept secret the process for creating toxic Victorian bookcloth, Tedone and Grayburn said they hope their research can be widely known in the field of library conservation. One goal of the Poison Book Project is to document every book that has been identified as being made with emerald green and eventually serve as a comprehensive reference for this and other toxic bookcloths. 

Additionally, they formed the Bibliotoxicology Working Group, an international group of librarians, conservators, historians, cultural heritage scientists and health and safety professionals. Their goal is to create standards for identifying toxic components in books and define best practices for keeping both the materials and the people safe.

Because few conservators have access to the tools necessary to conclusively test their collections, Tedone and Grayburn created a color swatch bookmark to help people visually identify books that might be bound in emerald green bookcloth. To request a color swatch bookmark, individuals can email reference@winterthur.org with “Emerald Green Bookmark” in the subject line and their name and postal address in the body of the email.

In the meantime, the scholars share simple steps that conservationists and private collectors alike can take if they suspect they have poison books in their collections.

First, never handle the book with bare hands. Wear nitrile gloves (like those used in medical offices).

Second, place the book(s) in a zip-lock plastic bag. Food-storage bags from a grocery store are sufficient for temporary storage. For long-term storage, polyethylene bags (which can be found on library storage supply sites) provide an effective barrier and will not leach gas or plasticized colors on the book.

And, importantly, don’t panic, the team said.  Much as household cleaning products are safe when used correctly, poison books are harmless if handled properly.

“It’s important to preserve these books,” Tedone said. “They have historical significance – the history of the book itself, evidence of manufacturing, for the history of trade.” Identifying emerald green bookcloth and establishing the Poison Book Project are just the next steps in library preservation.