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As it ages, white paper turns distinctive¹ of yellow, but why? To find out, scientists artificially aged² modern paper to rebuild the changes on the molecular³ level, the researchers in the Journal physical review of letters, for 48 days, 3 unpleached paper samples aged rapidly on reactors⁴ that's simulated in different environmental conditions, the researchers then compared the artificially aged samples to the real deal, 3 pieces of paper crafted in 15 century Europe, this technique allowed them to gauge⁵ the types and the months of changes going on, about 90% of the weight of old paper is cellulose, the sturdy material that makes plants so walls, but over time cellulose fibers⁶ oxidase, the process modifies parts of burriest molecules⁷ and turns them into what we call chromophores which absorb light, white paper is white because it reflect all colors of lights, aging paper filled with chromophores reflects wavelength⁸ that makes it look yellow, the non-destructive technique used in the study couldn't inform research to preserve and even widen in ancient * art and give paper conservation a brighter outlook.