Why the papers turns yellow over time
Why the paper turns yellow over time ?
Paper is made from wood. Wood mainly contains two polymers cellulose and lignin. Lignin also helps in protecting wood from pests and other damages.
It is the lignin that cause paper to turn yellow. Lignin has naturally dark colour, which is what makes wood hard and stiff.
Chemistry
Lignin undergoes oxidation when exposed to sunlight and air, and it breaks down into many phenolic acids that are yellow in colour.
This is why paper turns yellow in colour.
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