Bend Over Older Mature -

: As paper matures, it undergoes chemical and physical changes—such as the breakdown of cellulose chains—that make it brittle.

: If mature paper is stressed past its elastic limit or held in a bent position for a long time, the fibers shift permanently, causing the paper to stay bent even when the stress is removed.

: This specific physical property correlates with the Massachusetts Institute of Technology (MIT) fold endurance test , which determines how many times an older paper sample can be bent or folded before it breaks.