For 48 days, three unbleached paper samples aged rapidly in reactors that simulated to different environmental conditions. The researchers then compared the artificially aged samples to the real deal——three pieces of paper crafted in 15 century year Europe. This technique allowed them to gauge the types and amounts of changes going on. About 90 percent of the weight of all paper is cellulose, the sturdy material that makes up plant cell walls. But overtime cellulose fibers oxidized. The process modified parts of various molecules and turns them into what we called chrome*, which absorbs light. White paper is white because it reflects all colors of light. Aging paper filled with chrome* reflects wavelengths that make it look like yellow. The non-destructive technique used in this study could inform researchers to preserve and even whiten ancient textile and art. And give paper conservation a brighter outlook.