Naked Science Forum
General Science => Question of the Week => Topic started by: thedoc on 12/02/2008 17:31:46
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What is the smell of old books? The older the book, the better it smells. I’m not talking about the old mouldy smell of an ill-kept book. I’m talking about the heart-warming smell of a book you’ve loved and kept for twenty years. What is the smell of old books?
Asked by Thomas, Uttlesford
Read this Question from our Podcast (http://www.thenakedscientists.com/HTML/content/questions/question/1860/)
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We put this question to Jana, Head of Laboratory for Cultural Heritage at the University Library of Slovenia.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2F%2Fforum%2Fcopies%2FRTEmagicC_754px-Latin_dictionary.jpg.jpg&hash=7b9cfb44d46a400a86afb1d84a9f9ef3)A smell or odour is caused by volatile compounds which we perceive by the sense of olfaction. An odour of a book is a complex mixture of odorous volatiles, emitted from different materials from which books are made. Due to the different materials used to make books throughout history, there is no one characteristic odour of old books. A professional perfumer has evaluated seventy odorous volatiles emitted from books and described their smells as dusty, musty, mouldy, paper-like or dry.
The pleasant aromatic smell is due to aromatic compounds emitted mainly from papers made from ground wood which are characterised by their yellowish-brown colour. They emit vanilla-like, sweetly fragrant vanillin, aromatic anisol and benzaldehyde, with fruity almond-like odor. On the other hand, terpene compounds, deriving from rosin, which is used to make paper more impermeable to inks, contribute to the camphorous, oily and woody smell of books. A mushroom odour is caused by some other, intensely fragrant aliphatic alcohols.
A typical odour of ‘old book’ is thus determined mixture of fragrant volatiles and is not dominated by any single compound. Not all books smell the same.
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This is just speculation, but it's probably due to some combination of oxidation (which is the process that turns old paper yellow) and contamination with microorganisms such as mildew. Even books kept dry and contaminant free will probably pick up enough moisture and spores from the air to get a bit of mildewing.
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I think John (bored chemist) is away at the moment. Here is an answer he previously gave to the same question. Hope he does not mind me quoting it here?
"Books, like many other things, are subject to bacterial and fungal attack- particularly if they are not kept dry. The products of this decay include volatile organic chemicals like acetic acid and these are responsible for the smell."
Similary, this from Eric:
"Actually it is not the acid that is broken down (the acid used was - and is - aluminiumsulphate, also known as "paper maker's alum) but the lignin and some of the resin that are slowly broken down by the acid.
Alum is used for fixating the resin (it is the Al-ion that performs the trick), and the resin is used to make paper more waterresistant. At one stage, alumiumsulphate was replaced by alumiumtriformiate for making "neutral" paper, but this switch is rather expensive.
The use of alum and resin became standard in around the middle of the 19th century. Before that, water resistance was obtained by using animal glue (from bones). Both the "rags and bones" that were collected were mainly for the paper industry."
This from queequeg
"In addition to mold smells of various kinds, I have noticed that some old books have distinct vanilla notes in their smell. I attribute this to breakdown of lignin to give vanillin over time. Anybody else noticed this? "
And this from Bernard (that mad man)
"I thought that it may be that smoking was very popular several years ago, having a fag while reading maybe?"