Their report in the journal Analytical Chemistry identified acetic acid, furfural, and lipid peroxidation products in various proportions depending on the types of paper, binding and inks used, and they suggest that a "sniff test" may be useful to identify books in need of the attention of a conservator.
And how does one describe the smell of old books to a non-chemist? The next time you attend a wine tasting, deftly switch the conversation to books and tell your friends that what you love is...
"...a combination of grassy notes with a tang of acids and a hint of vanilla over an underlying mustiness."
Link. Photo: Tom Woodward.