What Is Emerald Green?

Emerald green is one of a suite of verdant pigments created in the late-18th through mid-19th centuries from copper acetoarsenite—a toxic arsenic compound. It was developed in 1814 by chemists Wilhelm Sattler and Friedrich Russ in Schweinfurt, Bavaria, in attempt to improve Scheele’s Green—a vibrant green pigment created in 1778. Other comparable variant colorants on the Victorian-era market included pigments known as Vienna green, Schweinfurt green, Paris green, and Schloss green. As a group, the pigments are similar in composition, color output, and worrisome arsenic content.

These pigments produce vibrant green tones that pop and were once widely used to achieve eye-catching deep greens in cosmetics, clothing, textiles, wallpaper, paint, children’s toys, and bookcloth until being discontinued from domestic use when health safety issues became apparent. The compounds were never banned and remained commercially available. Today, copper acetoarsenite is used in rodenticide, insecticide, and select colorants for fireworks.

Dangers of Arsenic

According to the World Health Organization, symptoms of acute inorganic arsenic poisoning include abdominal pain, vomiting, diarrhea, numbness, muscle cramping, and in extreme cases, death. Long-term exposure to high levels of inorganic arsenic can cause skin lesions, cardiovascular disease, diabetes, and cancers of the bladder, lungs, and skin.

During a lecture sponsored by the Grolier Club, Tedone remarked, “People interact so intimately with books. We hold them close to our faces. We leave them stacked up on our coffee tables within reach of children or pets. We curl up and read with a drink or snack in hand. We don’t expect a book we’ve checked out from the library to be covered in a deadly poison.” From tests Tedone and colleagues performed, results showed that an average-sized book “contained several times the lethal dose of arsenic for an average-sized adult.” But, Tedone stressed, “You would need to eat the book to ingest that quantity of arsenic” for it to be lethal. Despite knowing that people generally do not consume book materials, and they handle them only for a limited time, the presence of arsenic-based pigments in binding cloth still prompted Tedone and colleagues to survey their collections and consider ways to minimize dangers.

Investigations in the Stacks

Reeling from the lab findings, Tedone led a project to test books bound in green cloth published primarily between the 1840s and 1860s in Winterthur’s collections and later expanded the survey to look at emerald green cloth bound books in the Library Company of Philadelphia’s collection dating from 1837 to 1900. More than 10% of the books with green cloth bindings that the team surveyed contained arsenic. The team members published their findings in their publicly accessible Arsenical Books Database, a resource that expands as the team and other contributors identify books with arsenical colorants.

How Books Were Tested

Conservators on the Poison Book Project used a portable X-ray fluorescence spectrometer (XRF) to screen for the presence of copper and arsenic. This testing method is non-destructive and relatively swift. The team later employed another non-destructive test called Raman spectroscopy to confirm the presence of copper acetoarsenite.

In efforts to explore testing techniques and to quantify the amount of arsenic present, the team performed a limited number of destructive tests using polarized light microscopy (PLM). During PLM, scientists removed small samples from bindings suspected of containing emerald green pigments for analysis. The team also performed a limited number of microchemical tests to detect arsenic, but these rather complicated tests involve the “creation and measurement of arsine gas, arsenic’s most deadly form,” according to the team, and proved to be a complicated and potentially hazardous testing modality. In the end, the team recommended non-destructive tests such as XRF and Raman spectroscopy for the identification of emerald green arsenical books.

Color Swatch Bookmark

Knowing that many libraries and nearly all private collectors do not have access to sophisticated scientific testing equipment, the team developed a color swatch bookmark. It features high-resolution close-up photographs of book spines, in varying shades of green, taken from known emerald green books on one side, and handling tips and general project information on the other side. The bookmark is a tool to raise awareness about arsenical books and to aid in a visual identification of books likely bound in arsenical bindings. The team distributes bookmarks at no cost upon request. To receive a bookmark and information about the project, email reference@winterthur.org, list Emerald Green Bookmark in the subject line, and include a contact name and postal address in the body of the email. To date, the project has distributed 1,500-plus bookmarks to 49 of the U.S. states and 19 countries.

Arsenical Books Database

The project team maintains the Arsenical Books Database and solicits additional entries from institutions and collectors at large. The team provides data submission instructions and adds information about books identified with copper acetoarsenite content through analytical tests. It also lists volumes suspected of containing emerald green that were identified visually using the bookmark. The database lists titles, authors, imprints, dates, owners, and method of identification. The project team notes that “not every book from the same edition would have been bound identically [and] we provide this table of arsenical, mass-produced bookbindings as a starting point from which other institutions and private collectors may consider their own collections.”

Handling and Storage Tips

The Poison Book Project’s wiki page lists storage and handing recommendations to minimize personal exposure to arsenic.

Storage Tips

• Consider isolating arsenical books in archival zipper top bags or custom book storage boxes.
• Consider removing arsenical books from circulation.

Handling

• Avoid direct skin contact with arsenical books.
• Wear disposable nitrile gloves when handling arsenical books.
• Wash hands after handling materials, even when using gloves.
• Clean surfaces the book touched after use with a disposable wipe.
• Conservators treating arsenical books should perform restoration work inside a fume hood.

Earlier Findings

Tedone and her team were not the first to identify arsenic in library materials. In 2018, researchers at the University of Southern Denmark identified emerald green pigments in the covers of three 16th–17th-century manuscript covers, and according to JSTOR Daily, research librarian Jakob Povl Holck and associate professor in physics Kaare Lund Rasmussen speculated that earlier applications of “Paris green on old books could be to protect them against insects and vermin.”

At the start of the 20th century, and previously in the 19th century, the dangers of toxic green wallpaper were widely known, with many documented cases of severe illness and death. In the 19th century, emerald green wallpaper was known to be harmful, especially in damp environments, and it fell out of vogue as health concerns surfaced, notes WebMD. Similarly, too, the popularity and use of emerald green fabrics ceased as connections to illness became evident.

Interestingly, notes JSTOR Daily, in 1874, Robert C. Kedzie, a consumer activist from Michigan, created Shadows From the Walls of Death, an eight-page sampler book of Paris green wallpaper to raise awareness of arsenic dangers in the home. He created 100 copies and sent them to libraries in Michigan. Few copies survive, with the University of Michigan dubbing its copy “The Library’s Most Dangerous Book” in a 2015 blog post.

Conclusion

Although not the first group to identify the presence of toxic arsenic compounds in book bindings, the Poison Book Project team is leading a successful awareness campaign that helps recognize safety issues, provides resources to identify problematic books, and hosts a growing public database. The Poison Book Project is prompting libraries to evaluate circulation, storage, and treatment procedures. While best practices in this area are developing, the Poison Book Project has kick-started an important discussion and has given readers safety advice when engaging with books bound in emerald green cloth.

For more information, visit Winterthur on Instagram (@winterthurconservation) and Twitter (@WinterthurMuse) and search #poisonousbooks, #poisonbookproject, and #bibliotoxicology on Twitter.