How many times did you cut a clipping out of a newspaper to put it in your scrapbook only to find out years later that the paper has badly deteriorated and is almost impossible to read it? More than a few, right?
But have you ever wondered why? What causes paper to yellow over time?
Well, wonder no more you useless info junkies, because we have the answer. Here’s how it goes. (the article continues after the ad)
As we know, paper is made from wood. What you don’t know is that wood contains a polymer called lignin that binds the wood fibers together and it’s the one that turns paper yellow and brown. This is because the lignin molecules become less stable the more they are exposed to oxygen – they absorb more light and that’s why they have darker color. But why newspaper paper gets yellow way faster than white paper?
Normal, white paper goes through a chemical solvent process that dissolves lignin – and this is the reason why it will remain white and (normally) resist yellowing. But that’s not the case when it comes to the paper used for newspaper.
Since newspapers are only made to last for just a few days, newspaper production companies don’t really care about the quality of their paper. Their only concern is to get the cheapest one. That usually means unprocessed paper that has significantly higher percentage of lignin than white paper.
That being said, due to the fact that lignin makes paper stronger, we sometimes actually want it in paper. Take cardboard or brown grocery bags for example – we want them to be strong and study so we keep as much lignin as possible.
So now you know!
If you like what you read, then you will definitely love this one: This Is Why Jet Engines Have Spiral Shapes Painted On Them
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Sources: Ask a Science Teacher: 250 Answers to Questions You’ve Always Had About How Everyday Stuff Really Works | Why do newspapers turn yellow over time?