There's the old saying, 'never judge a book by its cover' and indeed you shouldn't - now chemists are saying you should judge them by their smell, instead. Publishing in the Journal Analytical Chemistry the authors have come up with a test that can measure how fast an old book is degrading, according to its odour. And this new sniff test could be really valuable to museums and document libraries because it has the potential to be completely non-invasive.
And we actually did a question of the week on this about a year and a half ago, with one of the authors on the paper. Jana Kolar, together with colleagues from University College London and Slovenia have isolated the 15 main VO Cs - volatile organic compounds - which the paper releases. Each of these volatile organic compounds are emitted from the paper as a result of: the original make-up of the paper in the document, the glues used to bind it and the ink used for the print.
The researchers looked at 72 papers from 19th and 20th centuries to find out which contained the most fragile components. They already knew these included rosin (pine tar) and wood fibre which are related to increased levels of acids, like acetic acid, in the paper as it ages. And these acids can eat away at the paper itself. So they collected and analysed the volatile organic compounds using a combination of gas chromatography and mass spectrometry. And then to 'test their own test' or find out which of these compounds were the ones libraries should be looking out for, they took a few small samples of the paper itself to look at its composition.
Combining the results gave them 15VOCs which give an indication as to the condition of the paper and how much acid or even peroxide/ie. bleach it's producing as it decays. They've dubbed the smell test 'material degradomics.' And now that they know the smell test works on these 72 samples they can develop this method to be completely non-invasive. And that's useful to any old documents library because currently, you have to actually cut a small sample from a document in order to test how it's faring.
And I'm sure many of you will have experienced these smells. They hit you like a slightly spongy wall when you walk into a well-established library like the ones you find here in Cambridge. The authors describe some of these smells as , "A combination of grassy notes with a tang of acids and a hint of vanilla over an underlying mustiness ."