These Green Papers Are Toxic And Could Be Deadly
In the spring of 2019, in Delaware, USA, Dr. Melissa Teiden of the Winterthur Museum checked out an old book published in 1857 from the library. It is a guide to home decoration, and the title of the book is “Country Country Decoration-For a Tasteful Home”.
The book is beautiful, and although it is more than a century old, it still retains its bright green exterior, which complements the gilt letters and patterns. As part of the collection to be exhibited at the Kunsthalle in Winterthur, the book’s striking colors are still impressive even though the spine and cover are about to fall off and the stitching is broken.
Dr. Tyden’s task is to restore the book before the exhibition opens. Under the microscope, she saw a black waxy substance attached to the book jacket. She tried to brush it off with a soft porcupine quill, but found that flakes fell off where the bristles passed. This might not seem unusual to outsiders, but Dr. Tiden was so surprised that she began to suspect that the jacket was colored with pigments rather than dyes.
Both pigments and dyes are colorants, but dyes are usually soluble, while pigments are insoluble and will be suspended in the liquid in the form of particles. If the book jacket is colored with paint, it is not difficult to explain why the coating is not very cohesive, and even the lightest touch from a quill is enough to take away a touch of color.
But when it comes to paints, especially green paints, Dr. Tyden can’t help remembering that this book was born in the 19th century, when certain bright and poisonous green paints were most popular. This made her start to worry. After meeting the old green book more than 100 years later, is she still suffering from the “fashion trend” of the past?
Green is so healthy, how can it be poisonous?
Green is probably the most common color in nature. However, it is not easy at all to turn this ubiquitous green directly into pigments or dyes for human use. Because the greens that people extract from plants are often very unstable, green at first, and then turn dull brown after a while.
It is difficult to collect stable green from plant components, and human beings can only turn more attention to minerals. For example, the ancient Egyptians mined malachite, ground it as green pigment, and used it in the paintings on the walls of some pharaoh’s tombs, which can be traced back to the fourth dynasty (2613 BC to 2494 BC). In the Renaissance period, many artists were still painting with malachite pigments. The main component of malachite is basic copper carbonate, which can keep its original color for a long time in both oil painting and tempera painting.
Since malachite, many copper-containing pigments have left their own green colors at different times in history. However, most of them may not be as famous as Scheler Green, which was born in 1775.
In 1775, a chemist named Karl Scheele slowly added arsenic trioxide (commonly known as arsenic) to a heated sodium carbonate solution to obtain sodium arsenite, and then poured the sodium arsenite solution into the copper sulfate solution. A copper arsenite precipitate was obtained, which is Scheler green. Its bright, non-fading color and low production cost made it an instant star product, leaving other green pigments in the cold.
This kind of pigment is not only active on the artist’s canvas, but also begins to enter every corner of human life. The wallpaper at home, the clothes on the body, and the children’s toys have all become the objects of Scheler’s green coloring. It is also sometimes used as a food coloring in candies. Although arsenic trioxide had been used as a murder poison in the Middle Ages before that, the toxicity of arsenic compounds was not widely known to ordinary people in the 19th century.
It was found that Scheler green would turn black when it encountered sulfide, so some people even wanted to create a more durable green pigment on this basis. In 1814, two German chemists improved the formula of Scheele Green, using arsenic trioxide and copper acetate to obtain copper acetate arsenite precipitation, also known as “emerald green”. After the birth of this dazzling new pigment, it followed the path of Scheler Green and was favored by many painters, and it invaded the lives of ordinary people on a large scale. Later, it had a more famous name – “Paris Green”.
The painting “Woman Doing Embroidery” uses Scheler Green
Scheele Green and Paris Green both led the color trend of the Victorian era. But as these arsenic-containing pigments became popular, so did the number of poisoning incidents associated with them.
The people who are most exposed to these pigments on a daily basis are probably the workers responsible for coloring the products. In 1861, a 19-year-old girl died who had used arsenic green powder to color artificial flowers in a London factory. By the end of her life, her nails and the whites of her eyes were green. An autopsy found arsenic in her stomach, as well as in her liver and lungs.
And when arsenic-rich goods leave the factory, consumers may become the next victim of arsenic. In London in 1862, in a family named Turner, the parents lost three children one after another, and a surviving daughter was also seriously ill. Originally, based on the symptoms, doctors believed that the children had diphtheria, a respiratory infectious disease that was very common in those days. Strangely enough, no one else who had been in close contact with those children ever contracted the same disease. Furthermore, the drainage and ventilation of the Turner home and the community where it is located are in good condition, and no serious health hazards have been found. Finally, the doctor finally suspected the green wallpaper in the patient’s home.
Soon after, the seriously ill child also died. After some chemists tested her tissue samples, they believed that arsenic poisoning might be the real cause of her death.
Since then, many similar incidents have made people gradually believe that those green pigments containing arsenic are harmful. Even if people do not deliberately touch them, the particles that fall off from them will float into the air. Cause physical discomfort, such as dizziness or diarrhea. Also, children and the elderly may be more vulnerable than healthy adults if they are exposed to arsenic for a long time.
Later, Scheele Green and Paris Green were gradually abandoned. These two pigments should be hard to find in green wallpaper these days. However, some items that have survived from the Victorian era may still maintain the color of the year, or the toxicity.
“Poison Book Project”
In fact, Dr. Melissa Teiden wasn’t just suspicious of a 19th-century book because she could easily scrape green flakes off the jacket. In addition, she also remembered that she had seen a Victorian green wallpaper pattern in a recently published book, which was very similar to the color of the old book she was restoring.
Dr. Tyden boldly guessed that the paint used on the book jacket was Paris Green. To confirm her suspicions, she turned to researcher Rosie Greyburn, who also worked at the Winterthur Museum. Greyburn first used X-ray fluorescence spectroscopy to analyze the elements in the green book jacket, and found that copper and arsenic were present, and the content was not low.
However, X-ray fluorescence spectroscopy can only determine the elemental composition of the sample. As for what kind of molecules those elements form together, further determination is needed. Graeburn uses Raman spectroscopy to study molecular structures. When the laser hits each molecule, it will obtain a unique scattering spectrum, which is like a unique “fingerprint” that distinguishes it from other molecules. This method allowed scientists to confirm that the pigment on the surface of the book was copper acetate arsenite-Paris Green.
The picture on the left is a wallpaper in Paris Green, and the picture on the right is a self-portrait of Van Gogh in Paris Green.
Raphael’s “Sistine Madonna” with malachite pigment
Analysis of 19th Century Books Using X-ray Fluorescence Spectroscopy
Books with Paris Green on the cover
Although his idea was confirmed, Dr. Tiden was still shocked: “I knew that there would be arsenic pigments in the wallpapers before, and I also knew that some illustrations in books would use arsenic pigments, but I didn’t expect this kind of toxic The cover is covered with something, and you will touch it when you hold the book and read it.”
Not only that, Tyden and Greyburn also found that the book jacket contained 1.42 mg of arsenic per square centimeter. The lethal dose of arsenic poisoning for adults is 100 mg. Dr. Teiden believes that he has only done some simple processing of this book and may not cause major harm, but if he is a library staff, he will face greater risks if he has more opportunities to be exposed to arsenic pigments .
Long-term exposure to inorganic arsenic may cause many health problems, such as skin damage, peripheral neuropathy and so on. There are also some cardiovascular diseases, respiratory diseases, liver diseases, and even cancers in some organs are also related to inorganic arsenic.
Therefore, the two researchers decided to launch the “Poisonous Book Project”, hoping to find more books that may be harmful to the human body from old books in the 19th century and catalog them. In the Winterthur library alone, they detected nine “toxic” collections, four of which were still circulating between different libraries. In the Library Company of Philadelphia (the oldest library in the United States), they found 28 old books containing Paris Green.
So far, Teiden and Greyburn have found 92 books with covers painted in Paris green. They also hand out “color comparison” bookmarks to help people identify which colors are more like Paris green in the 19th century. Whenever a suspicious object is found, the researchers still use ray fluorescence spectroscopy to detect elements as they did at the beginning, and if suspicious elements are found, they can be further confirmed by Raman spectroscopy.
Of course, identifying poisonous books is only a step in the plan, and what is more important is to reduce the harm of those books to people. Arsenic can be dangerous if it seeps into the skin of the hands, but especially if it is ingested through the mouth or enters the body through the respiratory tract, Greyburn said. In this regard, the “Poisonous Book Project” lists some precautions for people who need to be exposed to poisonous books:
Before operation, wear nitrile gloves and N95 mask. When operating, avoid eating, drinking and smoking, and keep the substances on your hands from touching your face; wash your hands after operation. In addition, do not operate on a soft surface (such as a sofa). You should place the poisonous book on a hard surface such as a table. After the operation, wipe the surface where the book was placed with a damp cloth to remove residual toxic particles.
Of course, a more fortunate and convenient situation is to never encounter these poisonous books. Although most of those libraries with collections from the mid-19th century will have a few bright green books, it may be difficult for ordinary people to come across. Also, not every green book from the 19th century was colored with arsenic pigments.