When we stroll down the hallways of libraries or any other places housing a massive collection of old books and historical manuscripts, one of the first things we’ll usually notice is the smell.
It’s a distinct kind of smell that many of us are familiar with.
Some people find the smell of old books pleasant, especially if they are well taken care of and haven’t fallen victim to unfortunate incidents that include spilled water and mould.
So what exactly causes the smell of old books?
It’s the result of hundreds of chemicals called volatile organic compounds (VOCs) emitted by the paper, according to a 2009 study by MatijaStrlic and colleagues, published in ACS Analytical Chemistry.
The study said that VOCs hold important clues to a book’s condition. By analysing the VOCs given off by old books, scientists can collect information that helps conservators preserve these historical artefacts.
Analysing VOCs isn’t an easy task though. Old books and historical documents can be fragile, and it’s important to avoid inflicting any damage on them while analysing their scents.
Some of the conventional methods to analyse the smell of old books require ripping out paper samples to be tested.
This may achieve the end goal but the downside is that part of the document is destroyed.
Because of this, scientists are developing other ways to “sniff” old books without damaging them. One of the recent studies that looks into a non-destructive method to sniff out old books was published in ACS Censors last year.
Titled Preserve Your Books through the Smell, the study includes assembling an “electronic nose” based on quartz crystals.
The researchers tested 19 books published from 1567 to 2016, classified by time period, paper composition, colour and visible state. VOCs emitted by these books were then collected and analysed with the electronic nose.
The electronic nose was able to distinguish between paper made from cotton or linen rags and paper made from wood.
It also distinguished books from different time periods.
Additionally, the electronic nose distinguished between books with yellow papers, a sign of paper degradation, and well-preserved books with papers, although they are made from the same material.
The study concludes that this method could help identify books in need of preservation.
It could also help protect books from VOCs emitted by nearby books on a shelf.
Aside from preserving the physical conditions of books, scientists like Cecilia Bembibre are also working towards documenting and archiving historic smells. One way to do this is by analysing VOCs of old artefacts – in this case, an antique book and a historic library.
In 2017, a study by Bembibre and MatijaStrlic was published in the Heritage Science journal. The study aimed to match the VOCs given off by an old book and a historic library to their scents.
Volunteers were split into two categories – one group described the smell of an antique book, and the other group described the smell of a historic library.
When describing the smell of the antique book, participants mostly used words like “chocolate”, “coffee”, “old” and “wood”.
Some participants described the smell as “socks” and “moth”, among other things.
On the other hand, the library smellers mostly used words like “woody”, “smoky”, “earthy” and “vanilla”. Over 70 per cent of the volunteers described the smell as “pleasant”, while 14 per cent rated it as “mildly pleasant” and 14 per cent as “neutral”.
By matching the VOCs given off to their scents described by the volunteers, Bembibre and Strlic developed the Historic Book Odour Wheel. With this wheel, you can match a VOC to its respective scent. For example, a book that smells like vanilla is caused by the chemical vanillin, whereas the caramel scent is caused by furfural.
The wheel represents “the first step towards documenting and archiving smells”, Bembibre and Strlic wrote in the article.
“By documenting the words used by the visitors to describe a heritage smell, our study opens a discussion about developing a vocabulary to identify aromas that have cultural meaning and significance,” said Bembibre in a press release after the study was published.
She shared that the wheel has the potential to be used to study a book’s state of decay, which will aid in preservations.
Bembibre also suggested the wheel could be potentially used to recreate smells in a museum, so that visitors know what it smelled like in the past.
But before that, further research is needed, she added.