Where does this come from, and can I check it?

Light and oxygen turn wood residues into acidic groups that darken the sheet. The figure is taken from Library of Congress, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.

Is this really a everyday life fact?

Yes. It sits on the Everyday Life shelf, one of 2,600 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.

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The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.

Mondo Knows Facts

Cheap paper yellows because of leftover lignin

Light and oxygen turn wood residues into acidic groups that darken the sheet Paper made from mechanical pulp keeps lignin, the brown polymer that stiffens wood, and that residue oxidises when exposed to light and air. The sheet yellows, turns brittle and eventually crumbles, which is why old newspapers age so badly. Archival paper uses purified chemical pulp plus an alkaline reserve to slow the decay. It sits in Mondo's everyday life collection, one of 200 facts that each trace back to the reference below.

Where this comes from

Library of Congress

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Tags: paper, chemistry, conservation

Cheap paper yellows because of leftover lignin: the short answers

Where does this come from, and can I check it?: Light and oxygen turn wood residues into acidic groups that darken the sheet. The figure is taken from Library of Congress, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.
Is this really a everyday life fact?: Yes. It sits on the Everyday Life shelf, one of 2,600 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.
What else can I read about it?: The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.