Yuri Gripas / Reuters

In an upstairs chamber at Knole House, there is a bowl of potpourri. It isn’t an attempt to make the place feel homey to visitors touring the more than 500-year-old stately home in the English countryside, nor is it a modern decorator’s afterthought.

The recipe was created more than 200 years ago specifically for Knole, using plants grown in its gardens. The scent is mentioned in the diaries of Vita Sackville-West, a poet who grew up there and whose family still owns the house. It is described in the novel Orlando, written by one of Sackville-West’s lovers, Virginia Woolf. The recipe even appears in a 1750s ladies’ magazine, says Cecilia Bembibre, a researcher who has studied its composition. This is a smell with a story.

But then—aren’t they all?

The smell of an old house on a hot, humid summer day; a whiff of the sea from over a grassy dune; gasoline spilled on pavement at the filling station; a perfume worn by your mother as she leaned over you. Scents are particularly powerful cues for memory, and they can even define a generation: A study found that those born after the 1960s report feeling nostalgic at the smell of Play-Doh.

Still, scents are ephemeral: A shift in climate or building techniques, or a product reformulation, can extinguish the smells of your youth. If you grew up in the country and move to the city, you will no longer smell rain in the fields. And you might be surprised to find when you go back that they have been built over and their scent dispersed.

Not very much of an effort has been made to preserve the smells that people care about. Bembibre, a graduate student at University College London’s Institute of Sustainable Heritage, is trying to understand which scents are worth hanging on to, what they consist of, on a molecular level, and how to save them. Her aim is to allow others, perhaps many generations down the line, to smell them, too, and understand why they mattered so much.

In a recent study, Bembibre and her advisor, the chemist Matija Strlič, focused on one particular smell already known matter to people: the fragrance of old books. Using it as a case study for how to characterize and record smells, they first placed sensors in the library of St. Paul’s Cathedral, where it is particularly intense. With a gas chromatograph and mass spectrometer, they identified many of the molecules responsible for the odor, and had seven subjects describe the scent. They also had visitors to a museum sniff a bottle with the reconstituted scent of a French novel from 1928 and record the notes that came to mind, from coffee to leather to mustiness. It turns out coffee and chocolate were most common, which makes sense: Coffee, chocolate, and paper are plant products. When cellulose in paper decays, it releases many of the same compounds as roasted coffee or cocoa beans do.

The researchers then created a diagram showing the words that subjects listed and the molecules likely responsible for them, which they call an odor wheel. Belimbre suggests this could be used as a kind of entry in an encyclopedia or a collection of preserved smells. “I’m exploring the concept of an archive of smell,” she says. “The odor wheel would be one of the pieces that would hopefully help reconstruct the smell in the future.”   

Thus far, there are few examples of such things. In 2001, the Japanese ministry of the environment asked the population which scents were particularly worth keeping, and out of more than 600 submissions, they selected 100, including the smell of a street of bookshops, of a particular kind of grilled eel, and of hot springs. But this is still a very unusual step to take. Bembibre has been working with the National Trust to characterize some of the smells of Knole House, including the potpourri and even the odor of the furniture wax.

Still, she feels that the decision of what smells are important should be made by a broader population of people. “I would like to have people vote on the smells that are important to them,” she says. “A smell can tell so much about the time and the society we live in.” While many answers are likely to be deeply personal, she wonders if there wouldn’t emerge a pantheon of scents that reflect this specific era. It might include the warm plastic smell of a computer casing, for instance, or rain hitting a particular modern formulation of concrete. Their universality might make a case for keeping them around as times change, so our descendants can get a fuller sensory picture of the past.  

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