Why do book pages turn yellow over time?

| Update:
March 16, 2022 12:57:09

Have you ever noticed that the pages of old books turn yellow over time? Those who have a collection of books know this phenomenon.

Well, fear not if you are encountering this for the first time. It’s nothing scary but pure science. Paper ingredients, when in contact with oxygen, turn yellow over time.

Paper is made from wood, which naturally includes cellulose and lignin that make wood strong and stiff. Cellulose, being a colorless element, is reasonable enough to echo light, which makes these papers white. As for lignin, a polymer, when exposed to air and light, its molecular structure changes.

Lignin is vulnerable to oxidation because it contains alcohol. Thus, additional molecules are required which stimulate the alteration of the structure of the polymer.

The added oxygen molecules break the bonds that simultaneously hold these alcohol subunits together, developing chromophores, a Greek word meaning color. The chromophores make it a bit yellowish or brown.

Less expensively prepared newsprint yellows even faster. The reason? It got more lignin than refined paper.

Block out air and light, and your books are safe

Although you can’t prevent the pages of your book from being yellow forever, with proper care you can keep them intact for a long time, even a lifetime!

Someone has surely caught your eye by passing books under sunlight to prevent bacteria from growing through them. Sorry to bust the myth for you.

Your book hates the sun’s rays so stop torturing them by keeping them in the sun. The ultraviolet radiation from sunlight is far too dangerous for books to yellow faster than usual.

So the first rule is to keep your books in a place where no light usually reaches. A bookcase or a drawer could be your solution.

Again, the bookcase you use should also keep air out, as air and light help turn them yellow.

Temperature fluctuations are another reason for this yellow tragedy of your favorite books. Never put your books in an air-conditioned room. Try to keep them in a cool but dry room where the temperature is constant.

Books that are already yellowish should be separated from undamaged books. This one is the least of your worries, but it’s a useful strategy to follow.

On the other hand, shelves can give off dangerous moisture that can help your books turn yellow, even after all the care. Use clothing, preferably cotton, that will absorb moisture.

You don’t have to throw away your books that have turned a bit yellowish. However, by being careful and following certain strategies, you can easily avoid the consequences.

The author is a third year student pursuing her BBA in Tourism and Hospitality Management at the University of Dhaka.

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Calvin W. Soper