Poisonous books – Dangers from the past

An exhibition looking at hazardous substances found in historic bindings is currently on display at the Research Studio in the Wardlaw Museum. This blog highlights the exhibition and the current research into tools for the identification of poisonous books being undertaken by Libraries and Museums with the Schools of Environmental and Earth Sciences and Physics and Astronomy.

Pigments used to colour historic books often contain hazardous substances, posing significant handling risks. Notably, arsenic combined with copper forms a bright green pigment known as emerald green, prevalent in 19th-century books. This vivid green was widely popular and used in various everyday items, including clothing, artificial flowers, wallpapers, paints, sweet wrappers, and even cake decorations.

Arsenical Pigments

Arsenic, a naturally occurring element, was known for its toxicity in the 19th century. Despite its use as a rat poison, arsenic was also incorporated into everyday items, including clothing, food, and household objects.

The emerald green pigment, containing arsenic, caused severe health issues such as skin ulcers, vomiting, hair loss, and even death.

Museums and libraries worldwide have inherited these items from the past but with more of an understanding of their dangers.  However, visual identification of which books are safe or harmful is not possible, as evidenced by the books displayed in the exhibition.

Identifying Emerald Green – The Visible Spectrum

A spectrum, or rainbow, is created when white light passes through a material like a prism, separating it into its component colours: red, orange, yellow, green, blue, indigo, and violet. These colours appear in a specific order based on their energy levels, with red having the lowest and violet the highest.

Light interacts with matter through reflection, refraction, and scattering. Scientists analyse the intensity of light in each colour to understand material properties. Historic pigments and dyes leave unique “fingerprints” on reflected light. Emerald green, a compound of arsenic and copper, has a very distinct light stamp that can be used to positively identify which books are poisonous.

Libraries & Museums heritage scientist, Dr Pilar Gil, used techniques which fall under the umbrella term of spectroscopy to discover emerald green’s unique fingerprint pattern.  Although spectroscopy is very specialized and costly, emerald green’s unique light stamp is being applied to an inexpensive handheld tool being developed in the University of St Andrews, in a collaboration of Libraries and Museums with the Schools of Environmental and Earth Sciences and Physics and Astronomy. This tool will enable everyone to test their old green books for poisonous emerald green.

What do we do with emerald green books?

Emerald green books are dangerous because the pigment flakes off making it easy to absorb, breathe in or ingest small pieces of arsenic when using the book.

Arsenic on emerald green bindings in University Collections is contained by storing them in Ziplock polythene bags.
When the books are used, we check first if there are any other copies available which are not bound in emerald green. If not, the book is handled with special precautions such as the use of nitrile gloves.

What’s in the current exhibition at the Research Studio in the Wardlaw Museum?

When you visit the exhibition, you will find:

• A video explaining the project and the research behind it.
• Large panels showcasing the everyday uses of emerald green in the 19th century and some of the science behind optics and emerald green.
• Books on display, some containing emerald green and others requiring you to guess if they do.
• Various activities, including wearing green glasses to reveal the letters of a secret word hidden on the first floor of the gallery.