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Examples of the green pigment containing arsenic from the Winterthur Library, Printed Book and Periodical Collection.
Not just a tool for
murder, arsenic was everywhere in the Victorian era. An abundant
by-product of mining operations, arsenic was considered harmless in
small doses, though its dangers were well known. It was sprinkled in
countless products – cosmetics, toys and textiles – even in medicines
and food in the mid-to-late 1800s. The era’s penchant for colorful décor
led to one of the substance’s best-known uses: as a pigment in popular
wallpaper patterns, especially those manufactured by William Morris,
chronicled by Lucinda Hawksley in her 2016 book Bitten by Witch Fever.
It was while reading Bitten by Witch Fever that Melissa
Tedone, affiliated associate professor of art conservation at the
University of Delaware and conservator and lab head for the Library
Materials Conservation at Winterthur Museum, Garden & Library,
realized the vibrant wallpaper patterns shown in the book matched the
hue of a bright green book she was working on in the Winterthur library,
Rustic Adornments for Homes of Taste, published in 1857.
Emerald green, sometimes called Paris green or Schweinfurt green, is a
pigment containing copper acetoarsenite, and its use in America and
England during the Victorian era is well documented. Given the toxic
elements’ ubiquity in everyday objects, some library conservationists
wondered if Victorian bookcloth could also contain poisons, but they
lacked the resources and equipment to test for toxic elements.
Enter UD expertise.
Move this whole section up, swapping places with the section above it.
Using XRF to analyze the elements present in a book cover from the mid-1800s.
Tedone consulted with Rosie Grayburn, affiliated associate professor
and associate scientist at Winterthur, and they agreed to act on
Tedone’s suspicion about her 165-year-old book.
For help, they turned to
UD’s College of Agriculture and Natural Resources’ Soil Testing
CANR’s Soil Testing Lab
began in 1947 as a public service to help farmers identify optimal
amounts of lime or fertilizer for their crops. Today, the lab still
tests soil for farmers and home gardeners, and it also provides
analytical services for researchers across campus, testing soil, water
and plant samples, as well as research materials like bones, food and
archeology samples. And, wildly enough, even books.
The lab confirmed dangerous levels of arsenic in Tedone’s emerald
green book. And although Tedone’s suspicions were correct, the news
still came as a shock.
“It’s one thing to use a pigment like that in a
small area in an illustration or painting, but this was the entire book
just covered with it,” Tedone said.
Melissa Tedone (left) and paintings conservator Matt Cushman examine a sample using a Hirox 3D digital microscope.
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.
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
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.
The Winterthur/University of Delaware Program in Art Conservation
(WUDPAC) and CANR’s Soil Testing Program provided the technologies for
each step that Tedone and Grayburn needed to make the Poison Book
Project successful, and there has already been significant impact in the
field of library conservation. The pair is contacted weekly by
colleagues around the world looking for advice on testing their own
Jess Ortegon uses a chemical test kit.
Working on the Poison Book Project offers art conservation students
the opportunity to get real-world experience, and, as Tedone said, make a
meaningful contribution to the field while still students.
Jess Ortegon, a third-year WUDPAC graduate student, worked on the
project during the summer of 2021, analyzing a selection of books
suspected of having chrome yellow bookcloth, a pigment that contains
They are currently at their third-year internship at the
University of Michigan, assisting the library with analyzing books for
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.
Victorian bookcloth, invented in the early 19th century,
revolutionized publishing. Previously, books could be bound either in
durable, but expensive, leather, or cost-effective, but flimsy, paper.
Bookcloth offered an affordable, durable option and could
be dyed or pigmented in bright colors that wouldn’t fade. Manufacturers carefully
guarded their bookcloth trade secrets, making it difficult for
conservationists today to track the use of specific compounds or
pigments that might contain arsenic.
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 email@example.com 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.
Article by Megan M.F. Everhart; photos courtesy of Winterthur Museum, Garden & Library
June 15, 2022