That smell has a cause that can be measured. It comes from the paper itself, and from what happens to it over the years.
The answer runs in order of cause and effect: what paper is made of, what happens as it falls apart, how scientists identified the chemicals, and what the smell can tell us.
What Paper Is Made Of and Why It Ages
Paper is an organic material, meaning it is made from once-living matter. As it ages, its components are broken down by acid hydrolysis, a reaction with water in the presence of acid.
Wood-based paper contains lignin, a tough natural polymer from wood. According to the International League of Antiquarian Booksellers, lignin is closely related to vanillin, the compound behind the scent of vanilla.
Paper made from wood pulp that still contains its lignin turns yellow, becomes brittle and deteriorates. Acidic wood-pulp paper became common in the late 19th century. Cheaper papers such as newsprint contain more lignin than finer papers.
What Happens as the Paper Breaks Down
As paper degrades, it releases volatile and semi-volatile organic compounds (VOCs) into the air. These are carbon-based chemicals that evaporate easily enough to drift from the page to your nose. Each has its own scent, and the overall smell is the mix.
The compounds released include vanillin (vanilla), benzaldehyde (almond), and ethyl-based compounds, toluene and hexanol, which smell musky or floral.
Lignin also oxidises over the years, reacting with oxygen to form coloured compounds and acids. That is why old paper yellows.
The blend differs from book to book. It varies with the paper's make-up (lignin, rosin and ash content, and acidity), the ink and binding, and how the book was stored and used. Matija Strlič describes the result as grassy notes, a tang of acids, a hint of vanilla and an underlying mustiness.
How Scientists Pinned Down the Smell
The key paper was “Material Degradomics: On the Smell of Old Books”, by Matija Strlič and colleagues. It was published in 2009 in Analytical Chemistry, volume 81, issue 20, pages 8617–8622.
The team worked at University College London’s Centre for Sustainable Heritage, with Tate Britain and the University of Ljubljana, Slovenia. They determined the main volatile degradation products of paper using headspace analysis, which means sampling the air around a material, after a 24-hour pre-degradation procedure. The study also measured the paper’s rosin, lignin and carbonyl group content.
In 2017, a study in Heritage Science by Bembibre and Strlič at UCL went further. It created the Historic Book Odour Wheel, a tool for documenting and describing the smells of historic books.
What the Smell Tells Us About a Book's Health
Strlič called the smell the smell of books dying. The research aimed at a non-destructive way to assess the condition of paper, so that a book’s state could be judged without damaging it.
The smell can work as a chemical signature of decay. Our noses pick up these compounds, and our brains interpret them as smells.
Why New Books Smell Different
A new book does not smell like an old one, because its scent has other sources. New books smell of the chemicals, inks and adhesives used to make and bind them.
The mix of smells in any book varies with the ink and binding as well as the paper. In an old book, those materials sit alongside the slow breakdown of the paper described above.
