CHEMISTRY PLAYS NOSTALGIA BEHIND THE AROMA OF BOOKS
Prof. Dr. Dhrubo Jyoti Sen*
When you walk into a library or a book store, the odor that works its way to your nostrils is a rather distinct one: the smell of old and new books. In fact, that unique smell is so loved that many avid readers still prefer physical books over the convenience of their digital versions (e-books). Books are made up almost entirely of organic materials: paper, ink, glue, fibers etc. All these materials react to light, heat, moisture and even each other over the years and release a number of volatile organic compounds (VOCs). While the blend of compounds released by any one book is dependent on the exact things that went into making it, there’s only so much variation in materials. Although new books are, well, new, they still give off a distinct odor. If you hold a new book up to your nose, you'll get a whiff of paper, ink and the book binding's adhesive. However, different books smell differently, because in today's modern age, different books use different chemical processes, paper treatments and adhesives in their making. This makes it difficult to determine specific chemicals that contribute to that smell, but all new books have three things in common: paper, ink and adhesives for binding. The process of creating paper from wood pulp itself involves a variety of chemicals, many which give off volatile organic compounds (VOCs), which release into the air and create odors. Then there's ink and adhesives, which also give off smells associated with books. However, it's the chemical compositions of older books that are most interesting. Although some readers like new book smells, it is old book smells that many are the most fond of and that chemistry is easier explained because the breakdown of compounds in the paper itself causes the smell. Older books have paper that contains a lot more cellulose and lignin, which come from the paper's original source: trees. These chemicals degrade and release VOCs, releasing scents that remind us of almonds, vanilla and flowers. The researchers tested 72 books and found some 15 compounds that came up again and again. They were reliable markers for degradation. These include acetic acid, benzaldehyde, butanol, furfural, octanal, methoxyphenyloxime and other chemicals with funny-sounding names. A book’s smell is also influenced by its environment and materials it encounters over the course of its life (which is why some books have hints of cigarette smoke, others smell a little like coffee and still others, cat dander). You can’t judge books by their covers, but the researchers think you can learn a lot from their odor. They're developing a method for determining the condition and age of books and other paper documents by using special “sniffing” equipment to analyze the blend of VOCs. They hope that this study of "degradomics" can help libraries, museums and archives assess and monitor the health of their collections and store and care for them accordingly.
Keywords: VOC, Adhesive, Water repellant, Bleaching agent, Cellulose, Lignin.
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