system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why is it when substances like paper dries off after it gets wet it's all crusty and roughish?
gpt
When paper is made, its wet fibers are carefully compressed and dried.  This allows the paper fibers to have their flat surface.  When allowed to get wet, finished paper absorbs the liquid and the paper fibers are allowed to decompress and they lose their flat surface.