You can learn a lot about the past by looking at old photos, walking through ancient buildings and rummaging through antique shops and historic archives. But you can also learn plenty by breathing in its smells.

In fact, according to a study in the journal Heritage Science, the odors of the past are part of our “cultural heritage,” as important to our understanding and connection with history — and as worthy of preservation — as the relics we can see and touch.

But how do you describe and document these culturally valuable smells so future generations can understand them and even reproduce them? The study’s co-authors, Cecilia Bembibre and Matija Strlič, decided to take a stab at this massive undertaking by focusing on a smell that most of us recognize immediately and love: old books. Their findings may aid historians in pinpointing and repairing damage in deteriorating historic tomes, plus the odor classification scheme they devised could help ensure that smells from the past live on.

The nose knows

You’ve probably experienced the power of smells to evoke old memories and trigger vivid emotions. The aroma of baking chocolate chip cookies, for example, may transport you instantly to your grandma’s kitchen. Or the smell of damp earth may ferry you back to your favorite childhood ravine.

In the same way, old books (specifically the historic paper and other materials used) give off unique moldy or sweetly musty scents that readers and history buffs know intimately and find pleasurable. For many, that “old book smell” elicits fond memories of childhood hours spent absorbed in beloved stories and discovering the world.

Learn more about the cultural importance of historic smells in this lecture by Strlič:

Judging a book by its smell

Bembibre and Strlič, both researchers at the University College London’s (UCL) Institute for Sustainable Heritage, started by analyzing the chemical signature of volatile organic compounds, or VOCs, emitted by old books using a gas chromatograph/mass spectrometer. Paper is made of wood, which gives off a mix of VOCs in the air as it decomposes, creating an odor.

Cecilia Bembibre samples VOCs in historic book Cecilia Bembibre samples the volatile organic compounds (VOCs) of a historic book at UCL’s Heritage Science Lab. (Photo: ©HMahgoub)

The co-authors and their team then asked visitors to the Birmingham Museum and Art Gallery in Birmingham, England, to describe eight unidentified smells, including the “old book” scent they’d captured, plus seven other unrelated scents like “coal fire” and “dirty linen.”

To their surprise, participants used the word “chocolate” most frequently to describe the book odor, followed by “coffee” and “old.” As Bembibre notes in this Popular Science article, “You tend to use familiar associations to describe smells when they are unlabeled. And also, the VOCs of chocolate and coffee seem to be very similar to that of books.” Perhaps not surprising, given that all three are derived from plants.

Bembibre and Strlič also collected VOCs from the historic library at St. Paul’s Cathedral in London (renowned for its distinctive “old book smell”) and asked visitors to take a similar sniff test. Instead of chocolate and coffee, this time participants used the adjective “woody” most frequently, followed by “smoky,” “earthy” and “vanilla.”

Why the difference? The researchers emphasize that the scent descriptors actually follow a plant/nature theme, but they speculate that participants may have been influenced visually by the library’s stunning interior woodwork and wooden furniture.

Finally, the team put everything together to create an odor wheel for historic smells, a descriptive tool combining scent adjectives and intensities similar to wheels used to characterize the flavor of wine or the fragrance of perfumes.

Getting a whiff of history

One benefit of the study could be to help preserve old books, which emit different odors based on where they’ve been (whether they circulated widely or sat on a shelf), and when and how they were printed.

“We know that books produced before approximately 1850 have a different smell to those produced between 1850 and 1990, and that’s because late 19th- and most 20th-century printing was dominated by acid sizing,” a process used on paper pulp to reduce water-absorbancy, Strlič told the Guardian. Understanding a book’s individual smell profile could help conservators more accurately diagnose various deterioration problems.

Bembibre extracts smell of bible Bembibre extracts the smell of an 18th-century Bible in historic Knole House, a 500-year-old English country estate located in Kent. (Photo: ©National Trust/James Dobson)

The research also could help history buffs bring their time travels into clearer focus. That is, museums and historic sites, which currently use visuals and sounds to animate the past, may now recreate the olfactory experiences of long-ago generations to provide a more multidimensional experience for visitors.

As the authors write: “In the heritage context, experiencing what the world smelled like in the past enriches our knowledge of it, and, because of the unique relation between odors and memories, allows us to engage with our history in a more emotional way.”