Arsenic in historic books: identifying the bindings at risk

In 2024, the Bibliothèque nationale de France withdrew from its shelves four nineteenth-century works whose green binding contained arsenic. German libraries had taken similar measures as early as 2023. Then, in March 2025, the French ministry for higher education and research published its recommendations for preventing the risks associated with arsenic salts present in historic collections.

The subject may sound spectacular. For libraries, however, the problem is far more concrete: how do you identify the works concerned among tens, or even hundreds of thousands of volumes?

Before being a safety question, it is therefore a question of identification.

Why are certain books affected?

Two green pigments are watched particularly closely.

Scheele's green, a copper arsenite developed in 1775, was gradually supplanted by Paris green, also known as Schweinfurt green, a copper acetoarsenite that is brighter and more stable. Both were used in the nineteenth century on binding cloth, endpapers and edges.

Their use falls mainly within a period running from the late eighteenth century to the late nineteenth, before arsenic-free pigments were gradually adopted.

And arsenic is not the only element to watch for. Historic collections may also contain mercury, lead or other metallic elements associated with certain pigments and dyes.

X-ray fluorescence for sorting collections quickly

This is precisely where X-ray fluorescence (XRF) becomes interesting.

Portable and non-destructive, it makes it possible to analyse a binding directly, without sampling and without moving the volume. The instrument is simply positioned above the surface to be checked.

In a few seconds, the spectrometer detects the chemical elements present. The simultaneous presence of copper and arsenic in a green binding of the period is a particularly strong indication that an arsenical pigment is present.

Reading the measurement correctly

XRF detects chemical elements, not pigments directly. Finding arsenic is therefore not enough on its own to formally identify a Paris green or a Scheele's green. To characterise the compound precisely, other techniques such as Raman spectroscopy may be required.

The measurement also remains sensitive to surface condition: varnishes, restorations or superimposed layers can limit detection.

Finally, a green binding is not necessarily arsenical. And arsenic can be found in colours or materials that are not green at all.

The real challenge: moving from diagnosis to a sorting campaign

In a large collection, the point is not to measure a few books one by one. A reproducible screening method has to be put in place.

That begins with defining the scope precisely: period of manufacture, type of binding, colour, provenance or collection concerned.

Then come the measurement protocol and the decision criteria: how many points per volume, which areas to check, how long to measure, and from what result a further analysis is triggered.

Finally, the protocol must set out what happens to the works identified: flagging, marking, handling or storage conditions. These measures then fall to the institution's conservation policy and to the recommendations of the competent authorities.

The BnF assessed the risk to readers as very moderate, and no case of poisoning linked to these works is documented to date. The aim is therefore not to respond to an emergency, but to know precisely what a collection contains, so that it can be managed on an objective basis.

From measurement to the field

At YSPEKH, we deploy portable X-ray fluorescence solutions for this kind of campaign and support users in defining the protocol, taking the measurements and interpreting the results.

But the institution does not always need the instrument itself.

For a one-off campaign, we can work directly on site, in a library, a storage area or a restoration workshop. The volumes therefore stay in their conservation environment: the instrument comes to them, the measurements are taken on the spot, and the results are handed to the institution.

A straightforward way of turning a difficult question — "which books are affected?" — into a measurable answer.

Sources: recommendations of the French ministry for higher education and research, 12 March 2025, on preventing the risks associated with substances containing arsenic salts in collections of historic books and documents; communication from the Bibliothèque nationale de France on the presence of arsenic in the bindings of nineteenth-century works.