Why does paper yellow?
When Bill showed us a yellowed page of newsprint from the ’60s for a recent show and tell session, we realized that, though we’re graphic designers that specialize in print, we couldn’t explain why the yellowing process happens. Why does paper turn yellow with age? After a bit of research, we’ve found the answer to quell our curiosity.
A substance called “lignin” is a component of wood which strengthens trees and keeps them upright. Because paper is made from wood, lignin is present in paper, too, but in varying amounts. Cardboard has a high amount of lignin, giving it its brown colour and stiffness. Cheaper paper like newsprint tends to not have as much lignin removed as better quality paper, which goes through a more-extensive removal process. Since lignin oxidizes when exposed to oxygen and sunlight, turning it a yellow-brown, paper containing enough lignin changes accordingly in hue over time.