Have You Wondered Why Pages In A Book Turn Yellow Over Time?

The Paper Is Made From Wood

Paper is generally made from the white cellulose of wood. Wood also has a dark substance called lignin, which is also an ingredient in paper-making.

About Lignin

Lignin is the compound that makes the wood and trees stiff as they stand upright. It also acts as a glue to bind the cellulose fibres together as well. It was found out that the exposure of lignin to air and sunlight is the main reason for the paper to turn yellow.

The Reason Why Papers Turn Yellow

The researchers revealed that when the lignin molecules are exposed to oxygen in the air, they tend to start changing and they become less stable. The lignin seems to absorb more light, which as a result gives off a darker colour.

The Less Lignin, The Whiter The Paper Is

It is revealed that if more lignin is removed, the longer the paper is said to remain white. While the paper manufacturers use the bleaching process to remove as much lignin as possible, the quality used for making newspapers and textbooks is cheap, and hence this is the reason you would find the papers and book pages turning yellow after a point of time.

The Paper Bags Are Sturdier

The manufacturers of brown paper grocery bags and cardboard shipping boxes revealed that they take advantage of lignin, as it makes the product sturdier. Since these products are not bleached, it leaves them with a much browner look than a regular newspaper. Hence, this is the reason due to which the bags become stiff enough.

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