Why did polyester shrink?

Question

I have a pair of pants that are 100% polyester and followed the instructions to cold wash and tumble dry (that means machine dry I think). However, they seemed to have shrunk. I recently bought more of the same type of pants but want to prevent it from shrinking. I've been drying the old pair with high heat in the machine. Should low heat be used for polyester?

Answer 1

The heat of your dryer caused the shrinkage.  Either use a low heat setting or line dry.