Why do old newspapers and book pages turn yellow over the time?

We all at some point of time come across piles and piles of old magazines and newspapers that kept in some dusty corner of the house and when we take them out during the annual house cleaning we find that what magic turned them way yellower than ever before.

Basically, there is no magic in it and it is all science in this why newspapers and book pages turn yellow over the time.

Paper is made of two main components, cellulose and lignin. Both of them serve the purpose of making the wood, from which paper is made, stronger and harder. Now, the cellulose doesn't change colour that much over the time but lignin turns almost completelyyellow when it is exposed to oxygen in the atmosphere.

This process of oxidation occurs, especially when the lignin comes in contact with the sunlight that completely alters the molecular structure of lignin and this changes the compound structure of it by absorbing and reflecting light. And that is why the paper changes its colour.

If you want to prevent those pages turn yellow then don't keep the paper in humid places because that acts as a trigger for the oxidation process and also, avoid touching it repeatedly to limit the yellowing.

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The main reason the pages of a book turn yellow is due to the amount of residual acid left in the paper. All of the suggestions from Mr. Gouvevia, and LIBSYS will delay the onset of yellowing, but sooner or later, paper containing trace amounts of acid will yellow over time,and become brittle.

Your best chance at avoiding the yellowing is to purchase books printed on acid free paper, and store them as suggested. This means no cardboard boxes, or other materials that may contain acid.