Why do old books smell like that?
Do you enjoy the smell of old books? Even if you don’t, you can feel a certain nostalgia when you step into a library or a bookshop. There’s a reason why old books smell like they do. Have you ever wondered how they manage to keep that scent for so long? It’s because they’re made out of cellulose and lignin, which are very flammable and burn in a specific way. The books are bound together by the chemicals, keeping them intact and turning them into something like a giant piece of wood. This is why they burn slowly, which is different to how paper burns. The decomposition of the chemicals leaves behind the scent and it’s what makes them unique and special.
Lignin is a fascinating polymer. It’s what gives wood its rigidness and is vital for a plant’s survival. It’s a tough compound, but in the presence of certain compounds, it can easily be broken down. One of my favourite compounds to break down Lignin is Hydrogen Peroxide. It’s a mild oxidizer so it breaks down Lignin slowly, which is why it’s so safe to use. You can also use Lignin to clean your hands! It’s an affordable, effective way to reduce bacteria on your hands. Use a Lignin/Hydrogen Peroxide blend and rub it onto your hands, then rinse it off with water. It’ll take away essential oils and other impurities on your hands.
Lignin is a substance that is often found in wood. Under the influence of oxygen, lignin decomposes into acids, which break down cellulose fibres. The lignin can be degraded by spreader enzymes or white-rot fungi. Both processes remove lignin from the wood. The spreader enzymes can break down the lignin by less aggressive means than the fungi, but they are unable to penetrate the lignin present in the wood to any depth. Thus, the white-rot fungi are the only organisms that are capable of removing the lignin from the interior of the wood.
References:
Fengel, D., & Wegmann, M. Lignin and Lignans: Advances in Chemistry. CRC Press, 2003.
Browning, B. L. Methods of Wood Chemistry. Wiley-Interscience, 1967.