The fabric of traditional clothing does not withstand the book binding process and is not strong enough to serve as a cover. In the 1820s, publisher William Pickering and bookbinder Archibald Leighton developed the first commercially viable process of coating cloth with starch, filling in gaps in the weave to produce a strong material: the first canvas.
“It was a game changer,” according to Tedone. “Cloth was much cheaper than leather, which meant you could now sell books at different prices. The process not only affected the results of the publisher: it revolutionized reading in general. “They were making books accessible to a much broader population, serving people at all levels of the economic ladder. »
The popularity of cloth-bound books exploded in the 1840s, making the process of creating cloth binding a closely guarded secret. “It was a lot of money for the publishers and, unfortunately, there are few documents on the manufacturing process of the binding cloth”, explains the specialist.
What we do know is that book covers can suddenly take on a wide variety of hues. Booksellers produced a range of books in various colors using dyes, which are solutions that chemically bond to the substance to which they are applied, and pigments, which are materials that physically coat the substance, such as dried mud on a pretty dress. Sunday. The most fashionable shade of green pigment at that time could thus adorn the covers of popular books.
However, the problem with pigments is that they tend to crack, chip, and crumble over time.
POISON IN THE LIBRARY
In the spring of 2019, Melissa Tedone received a request from a Winterthur gallery curator to borrow a book from the library for display: Rustic Ornaments for Homes and Tastespublished in 1857.
“This particular book was very beautiful, bright green with lots of gold patterns. It was visually impressive, but it was in very poor condition,” he explains. “The spine and covers were coming off, and the stitching was torn. Therefore, it was necessary to preserve it before it could be put on display. »
After placing this beautiful but damaged book under his microscope, Tedone examined the cover. “There was a black, waxy grime on the surface, and I was trying to get it off the canvas with a porcupine quill,” she says. “And then I noticed that the dye on the canvas was flaking off very easily around the area I was working on. »
To the untrained eye, this may seem normal for a 162-year-old book, but to this specialist it was surprising. “It didn’t look like the fabric was dyed,” he said. “It seemed to me that the starch layer of the fabric was possibly mixed with a pigment. »
To find out the identity of the mysterious green pigment, Tedone approached Rosie Grayburn, director of the museum’s scientific research and analysis laboratory.
Ms. Grayburn first studied the sample using an X-ray fluorescence spectrometer, whose job it is to bombard the material with X-rays and measure the energy of the emitted photons to determine its chemical composition. This technique allows knowing the elements present, but not their arrangement in a molecule. Another technique using a Raman spectrophotometer measures how light from a laser interacts with target molecules, moving the laser energy up or down. Just as each person has unique fingerprints, each molecule has a characteristic Raman spectrum.
The sensitivity of these techniques is essential, but it is equally important that they are non-destructive. “You don’t want to damage the artwork,” says Grayburn.
X-ray fluorescence revealed the presence of copper and arsenic in the green pigment, a key finding, and the unique fingerprint of Raman spectroscopy identified the pigment as the famous Paris green.
MANAGEMENT OF TOXIC BOOKS
The team then used the University of Delaware Soil Testing Laboratory to measure the amount of arsenic present in the canopy of Rustic Ornaments. He found that the canvas contained an average of 1.42 milligrams of arsenic per square centimeter. Without medical attention, the lethal dose of arsenic for an adult is about 100 milligrams, or the mass of a few grains of rice.
“What are the consequences of having so much arsenic in the bandage, in the gloves, during the treatment? What does this mean for health and safety? Grayburn asks.
To answer these questions, Tedone and Grayburn contacted Michael Gladle, director of environmental health and safety at the University of Delaware. “Arsenic is a heavy metal to which certain toxicity is associated, mainly through inhalation or ingestion,” he explains. The relative risk associated with the emerald green web is “frequency dependent” and is a major concern “for those working in conservation. »
Gladle suggests that anyone handling these books isolate them and work with them on a flat table with fume hoods to control for any arsenic particulate matter. “People who have access to these old books for research purposes should wear gloves and use a dedicated space to examine these books,” she adds.
Following Gladle’s recommendations, the Winterthur Library removed nine arsenic-covered green books from circulation and placed them in large sealed polyethylene plastic bags. When handling or preserving affected books, wear nitrile gloves, then clean hard surfaces and wash hands.
The team then set out to find other books, traveling 25 miles to the oldest library in the country: the Library Company of Philadelphia. They identified an additional twenty-eight books on emerald green canvas. Using a larger sample, they found that most of the books whose emerald-green canvas contained arsenic had been published in the 1850s.
To help others identify arsenic-coated books and the potential risks they pose, the team designed full-color bookmarks emblazoned with images of Paris’ green covers, along with safety precautions for handling and storage. It shipped more than 900 of these markers throughout the United States and to 18 other countries, enabling 6 other institutions to identify books containing arsenic in their collections.
Despite the toxicity of arsenic-based Paris green in household products, wares, and clothing, it was never banned. Its use died out naturally, either because of its reputation as a toxic substance or because the color simply fell out of fashion, much like avocado-green appliances in the 1970s.
Tedone’s most important message, as a good curator, is not to throw away poisoned books. “Don’t panic and throw them in the trash,” she says. “We just want people to take this seriously. »