I once had a geology friend who, when we went hiking, would taste (well, actually lick) the rocks to identify them. Apparently you can do something similar with books — judge them by their odor. According to this article in Wired,
Just sniffing an old book can tell chemists a lot about the state of the paper in a vintage volume, including its level of acidity, lignin and rosin, which are all important variables for deciding how to approach preserving the text.
This next quote from the article caused me to stick my nose in a few volumes on my bookshelf — unfortunately the hint of vanilla was definitely missing, more noticeable was old sock.
“The aroma of an old book is familiar to every user of a traditional library. A combination of grassy notes with a tang of acids and a hint of vanilla over an underlying mustiness, this unmistakable smell is as much part of the book as its contents. ” —Matija Strlic, et al, in Analytical Chemistry
Apparently you can also taste the pH of paper if you’re really good.
I remember 40 years ago, when I got my first job in the book world, in an antiquarian bookstore, my first impression was “that old book smell”. I think I fell in love that moment and spent the rest of my life in pursuit of old books. Working with rare books, I found they were beautiful, fascinating, and more often than not had that certain smell.