(Not sure if the flair should be Chemistry or Physics…)
In: 50
I remember a high school chemistry teacher explaining that it’s essentially the same process that happens when something burns except it’s very very slow.
Never understood ELI5 questions that can be answered by just typing the title of their post into Google and getting their answer…
Oxidation of unpure cellulose. While new paper has a lot of additives, the lignin of old pages oxidise slowly under sunlight and water and turn yelow