system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does paper lose its flatness after touching water then drying?
gpt
Uneven drying. When paper gets wet, it ever so slightly expands as it absorbs water. Sine the entire piece doesn't dry completely at the exact same time, some spots will contract at different rates until the paper is too dry to be pliable to the drying process, in which it 'locks' into a wavy pattern.