The 'Old Book Smell' Phenomenon Is Easily Explained By Science

Every bibliophile knows it, loves it, craves it — the smell of a well-read book. It's so popular that you can even find old book-scented candles, but what creates that signature smell? The answer is a little morbid, because what you're really smelling in the pages of old books is the scent of dying plants. After all, paper is made from plant fibers. These can be derived from straw, bamboo, flax, and many other sources, but in the modern day, the most common material for paper by far is wood pulp. Since trees are living organisms, paper is an organic material, and as with all organic things, it decays as it ages.

The plant fibers used in papermaking are largely made up of cellulose, a sturdy polymer with good durability. However, plants also contain a different polymer called lignin, which is far less durable. Over time, as paper is exposed to the air, the lignin within it begins to oxidize and break down into acids. These in turn trigger acid hydrolysis, a chemical reaction that causes the cellulose in paper to break down as well.

As the plant fibers in paper break down, they release volatile organic compounds (VOCs), chemical compounds that vaporize at room temperature. VOCs are responsible for almost all of the aromas we smell, from the sweet scent of flowers to the noxious odor of gasoline to, you guessed it, old book smell. It begs the question, if this aroma comes from decaying plant remains, why do so many people find it appealing?

In 2014, Dr. Oliver Tearle of Loughborough University coined a term for the smell of old books: bibliosmia, a portmanteau of the Greek words for "book" and "smell." Like petrichor, the smell that comes before rain, bibliosmia evokes a strong emotional response in many people that has fascinated researchers. Part of the appeal is contextual — for people who love books, their scent is a natural comfort. Smells can also be a reminder of specific places and moments from the past, and old books may evoke nostalgic memories of libraries, bookstores, and grandparents' shelves.

The appeal of old book smell isn't entirely in the mind, however. Amongst the hundreds of volatile compounds released from paper and ink, many people notice a particularly appealing scent standing out, a note akin to vanilla. This is no figment of the imagination. Lignin has a very similar chemical structure to vanillin, the compound in vanilla beans that gives them their beloved aroma and flavor. As the lignin in paper breaks down, it releases similar VOCs to vanilla. A hint of grassiness also accompanies the plant-based material, evoking the woodland roots of the paper. These aromatic compounds blend into something reminiscent of cookies baking in a log cabin. It's no wonder that we find them so comforting.

Though today's papermaking process involves turning trees into paper, that process has gone through significant changes over the course of history, and the smell of old literature depends on the material it was written upon. From the invention of the printing press in the 15th century all the way through the 18th century, paper was typically made from rags of cotton or linen. These materials are very high in cellulose, creating a durable paper that does not degrade easily. However, as literacy around the world advanced and demand for books increased, manufacturers began searching for a cheaper material to print on. This culminated in the introduction of paper made from wood pulp in the mid-1800s.

Cheap wood pulp allowed books to be printed and dispersed on an unprecedented scale, but there was a drawback. Wood has a very high lignin content, resulting in paper that breaks down easily. In addition to causing old book smell, this breakdown is the reason that old books typically have brown or yellowed pages.

The aroma we refer to as "old book smell" is most prominent in books that were printed between 1850 and 1990. The end of the 20th century brought about new papermaking practices, which include the use of several chemicals to bleach the paper and make it stronger. Since this process is only a few decades old, none of the books printed this way have had much time to age, but as they do, they won't give off the same old book smell people love.