Lunch Hour Lectures on Tour: A book by any other name would smell as sweet

The UCL Lunch Hour Lectures, currently on tour to the British Museum, offer the free chance to break up a busy working day with a thought-provoking mini-lecture. I went along to the third instalment on 21 June, which was given by Dr Matija Stlic from the UCL Centre for Sustainable Heritage.

Dr Strlic’s job is one of those that you never found out about in career days at school; he uses applied chemistry to protect our cultural heritage. This week’s talk was all about his work on paper and the importance of its smell.

There’s nothing quite like a smell for triggering memories. Like many other people, I think the smell of old books takes me back to many happy places; finding old family documents in the back of my grandparents’ cupboards, wandering through old libraries with my parents, or rooting through second-hand bookshops as a student.

Never before had I thought to ask where this smell comes from, but I soon found out as Matija gave us a quick tour of the history of paper production.

Originally, it was made from any combination of plants, rags, waste and anything else that could be pulped into a suitable material.

Paper production reached the UK around the 15th century, by which time the recipe had been tweaked to the primarily plant-fibre mix we know today. Around the mid-19th century, however, there was a change to the production, in order to make the process more environmentally-friendly.

Before this change, rosin (dried tree resin) was used to ‘size’ the paper, a technique akin to glazing, which stops the ink absorbing into the paper like blotting paper. Alum (an aluminium salt) was used to precipitate the rosin onto the paper.

Unfortunately for us and our historical documents, alum is acidic. That means that now, around 80% of the papers in our archives, libraries and repositories are themselves acidic and prone to degradation.

Another major factor that influences how likely a book is to degrade is it’s lignin content. Wood is primarily composed of two substances; cellulose, which makes up the plant cell walls, and lignin, which provides strength and structure to the plant.

Cellulose was then, and remains, the base ingredient for paper today. Lignin, however, is unstable, leads to increased paper degradation and causes the yellowing of old paper after exposure to light.

Much of the information contained in the works in our archives is irreplaceable; once it’s gone, it’s gone, and our cultural heritage would suffer immensely from its loss.

This is where Dr Strlic steps in. He is part of a collaboration that has developed non-destructive techniques to allow measurement of the volatile compounds that old books and documents give off. These volatiles are sampled and submitted to a process of gas chromatography, a technique that allows us to tell which chemicals are being produced.

By ‘smelling’ our old books in this way, he can tell what they’re made from and how fast they are degrading by looking for chemicals associated with the presence of alum and lignin. This can inform preservation strategies, or perhaps affect the prioritisation of digitisation or reproductions.

As ever, this lecture proved to be very interesting. I’d never before considered books to be a complex, dynamic chemical system, but that’s only because I’ve never been faced with the problem of curating thousands of old books and manuscripts.

We need research such as this to make sure we can preserve as much of this heritage as we can, so that it can be studied and enjoyed for years to come.

There was one thing I didn’t enjoy finding out. You know that wonderful sweet, musty vanilla bouquet that so characterises old books? Lovely isn’t it. Or maybe not.

This smell is actually a by-product of lignin degradation and the smellier the book the more prone it is to falling apart as it gets older. I’m not sure if I can enjoy it quite so much now.

Image source: Wikimedia Commons

James Heather is a first year PhD student in the UCL Division of Infection and Immunity.