Towels are often the stiffest victims because of all the built-up lint and mineral deposits. Here’s a pro tip: wash them with no detergent and a cup of white vinegar every few months. It strips all the residue away.
Then, follow with a regular wash using a tiny amount of detergent. Seriously, you only need a tablespoon. Over-soaping is the #1 cause of towel stiffness. After washing, tumble dry on medium heat with the tennis balls—your towels will come out so fluffy you’ll want to hug them.
How To Soften A Stiff Quilt at Harold Herron blog