Old books have a distinctive smell that can make any book lover’s heart melt. Matija Strlic of University College London described it to The Telegraph as “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 a part of the book as its contents.”

The secret to the scent is within the hundreds of volatile organic compounds (VOCs) that make up the book’s paper pages, ink, and adhesive. Over time, the VOCs break down, releasing the chemicals into the air that are picked up by our noses. New books also have a trademark aroma, but it isn’t quite as developed as their older counterparts. Additionally, different materials used in manufacturing the book will alter the VOC profile.

Compound Chemistry reports that hints of almond are created by benzaldehyde, while vanillin emits notes of vanilla. Sweet smells come from toluene and ethyl benzene, and 2-ethyl hexanol produces a light floral fragrance. Additionally, the book can also retain some odors it has been exposed to during its history, such as smoke, water damage, or pressed flowers between the pages.

Knowing why paper smells as it does is more than just a fun fact; it could be used to help libraries “sniff out” which books and papers are in danger of degradation. Identifying these aging manuscripts could allow them to be preserved and protected. Strlic led a study published in Analytical Chemistry in 2009 that found 15 VOCs which break down more rapidly than others.

If you’ve switched to an e-reader but miss the smell of old books while you read, there are many options for candles, perfumes, and air fresheners that will help your room smell like a comfy old library.

[Header image by Ryan Franklin via flickr, CC BY 2.0]