system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why do clothes get hard if you hang them to dry?
gpt
There will be a little bit of residue in the water left on the fibres in the clothes. As they dry, that residue, soap scum, salts from water hardness, etc will dry out and weakly glue the fibres together so they don't slide over each other easily. A bit of wear or handling will break those bonds.  Starch does the same thing when you deliberately want something like a crisply ironed shirt.