system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does a previously wet paper become crinkly and more rigid after drying up?
gpt
Before becoming wet, all of the paper fibers are neatly aligned. This allows the paper to bend predictably and smoothly Once wet, all of the fibers swell in place like individual sponges, which puts the fibers into disarray. That disarray makes its appearance to us as a stiff, wrinkly paper.