Why are towels stiff after air drying?

I don't know why it happens, but if you like (or have to) hang your clothes and towels out to dry, using a good fabric softener will keep your towels from getting stiff like that. ha ha i use to think they could walk in on their own as stiff as they were.

The tumbling of the dryer softens the material up, whereas the hanging items are still and dry that way, creating stiffness.

You should always use a good liquid fabric softener when you line dry towels. However, it could be the quality of your towels. I have some older ones that are still stiff, even with the softener, and then I have some newer ones that are better quality plush towels and they are always very soft, even after line drying.