Death By Reading? Danish Library Researchers Discover Poisonous Books

Researchers were looking for hidden manuscripts between the bindings of old books when they discovered the potentially life-threatening poison covered books.


Working at a library is not usually a deadly job but for a pair of researchers, analyzing old books potentially became life-threatening after they came across poisonous books.

Researchers Jakob Povl Holck and Kaare Lund Rasmussen from the University of Southern Denmark recently stumbled upon three books covered in deadly arsenic, dating back to the 16th and 17th centuries.

Holck and Rasmussen were looking for hidden manuscripts between the bindings of old books when they discovered the potentially life-threatening poison covered books.

In a well-documented book recycling process, European book-binders would usually place medieval manuscript fragments between the bindings of the books to make them stronger. For library archivists, these manuscripts are like hidden treasures where they try to read what is hidden within the covers of historically old books.

Library archivist informed Holck and Rasmussen of the presence of such a manuscript within the bindings of the three books but a thick layer of green paint made it near impossible for the researchers to read the Latin text.

In order to separate the chemical elements of the ink used to write the manuscript from the paint on top, the two used a scanning technique known as X-ray fluorescence analysis, or micro-XRF. This particular technique is usually used to examine the chemical elements of ancient pottery and old paintings.

However, the results were not what they expected. To Holck and Rasmussen’s shock, the green paint was, in fact, arsenic.

Arsenic is a highly toxic and potentially life-threatening substance. Contact with arsenic can lead to poisoning, cancer and even death.

The covers of the books were painted in “Paris green,” an emerald green color which used arsenic pigment top reach its desired intensity.

“The arsenic pigment—a crystalline powder—is easy to manufacture and has been commonly used for multiple purposes, especially in the 19th century. The size of the powder grains influence on the color toning, as seen in oil paints and lacquers. Larger grains produce a distinct darker green—smaller grains a lighter green. The pigment is especially known for its color intensity and resistance to fading,” the researchers explain in their “Conversation” article.

“Industrial production of Paris green was initiated in Europe in the early 19th century. Impressionist and post-impressionist painters used different versions of the pigment to create their vivid masterpieces. This means that many museum pieces today contain the poison. In its heyday, all types of materials, even book covers and clothes could be coated in Paris green for aesthetic reasons. Of course, continuous skin contact with the substance would lead to symptoms of exposure,” they wrote of arsenic’s use in paint manufacturing in the 19th century.

“But by the second half of the 19th century, the toxic effects of the substance were more commonly known, and the arsenic variant stopped being used as a pigment and was more frequently used as a pesticide on farmlands. Other pigments were found to replace Paris green in paintings and the textile industry etc. In the mid 20th century, the use on farmlands was phased out as well,” the researchers added.

However, according to Holck and Rasmussen, the paint used here was not for decorative purposes but to keep vermin and insects away, thanks to arsenic.

Although now, the books have been stored in separate card board boxes with a warning sign plastered on them. The books would soon be digitized to decrease the need for handling.

So the next time you go to a library, better think twice before you lick your fingers to flip a book page.

Thumbnail/ Banner Credits: U.S. Immigration and Customs Enforcement/Handout via REUTERS

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