Sniff test gauges book degradation

Scientists from University College London (UCL) have developed a test that can measure the degradation of old books and precious historical documents on the basis of their aroma.

In a report published in the American Chemical Society’s Analytical Chemistry, they describe how the non-destructive 'sniff' test could help libraries and museums to preserve a range of prized paper-based objects, some of which are degrading rapidly due to advancing age.

Matija Strlic and colleagues at UCL's Centre for Sustainable Heritage note in the study that the well-known musty smell of an old book is the result of hundreds of volatile organic compounds (VOCs) released into the air from the paper.

The aroma of an old book is familiar to every user of a traditional library, Strlic said. 'The unmistakable smell is a result of the several hundred VOCs off-gassing from paper and the object in general. The particular blend of compounds is a result of a network of degradation pathways and is dependent on the original composition of the object, including paper substrate, applied media and binding.'

Those substances hold clues to the paper’s condition, Strlic said. Conventional methods for analysing library and archival materials involve removing samples of the document and then testing them with traditional laboratory equipment, but this approach involves damage to the document.

The new technique - an approach called material degradomics - analyses the gases emitted by old books and documents without altering the documents themselves.

The scientists used it to 'sniff' 72 historical papers from the 19th and 20th centuries. Some of the papers contained rosin (pine tar) and wood fibre, which are the most rapidly degrading types of paper found in old books. The scientists identified 15 VOCs that are seen as good candidates for markers to track the degradation of paper.