You either love or despise the smell of wrinkled, weathered pages in well-used books, but scientists have discovered a way to harness that odor to help preserve rare texts.

For most people, the aroma of an old, well-loved book is familiar and strangely pleasant. Scientists have previously determined that when manufacturers use wood (which always contains a material called lignin) to create their pages, the books will most likely throw off scents of vanilla as they age, according to Smithsonian magazine. Other common scents include whiffs of almonds, caramel, and chocolate; depending on the volatile organic compounds (VOCs) used in creating the book, you might also detect odors related to formaldehyde. But a keen sense of smell hasn't helped bibliophiles actually preserve books. Instead, most experts have to use techniques that require taking paper samples from books that historians would rather not tamper with in order to understand their condition—until now, that is.

Sharing their new findings in the journal ACS Sensors, a team of researchers from the University of Aveiro in Portugal have developed a new "electronic nose" that can sniff out books' odors regardless of the pages' composition. This will help experts determine if books are degrading or are in good condition without having to destroy any of their pages during testing. Since most books made prior to 1980 are made with paper from wood-pulp fibers, these books are much more sensitive to testing; the same is true of tomes printed in the 18th century and earlier, since sturdy cotton and linen were used to create centuries-old pages. 

Old Vintage Books in a Pile
Credit: Sean Gladwell / Getty Images

Regardless of when it was made, most books throw off VOCs as they age. The researchers on this project collected 19 different books published between 1567 and 2016; they classified each books' paper composition and visible state. Then, they collected VOCs released from the books, and were able to classify these gases with an electronic nose containing six different sensors. Their gadget accurately distinguished between cotton and linen paper from wood-based paper, as well as distinguished the books among their vastly different time periods. 

Most excitingly, however, the researchers noted that using odor alone, their machine was able to sniff out yellowing books without any other method of testing involved. While the team behind the discovery plans to conduct more research, this highly sensitive technique could help preservationists protect more books than ever. At one point, it may even help all homeowners who have a library prevent books emitting VOCs from affecting other books on the shelf—imagine that!


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