If you put away your paintbrushes when they were still wet from cleaning or if you stored them in a crowded toolbox, you might wind up with bristles that are all bent out of shape. It's a bad idea to paint with such a brush, because you'll wind up with messy brushstrokes and you'll also increase your odds of dripping paint as you brush it on. Fortunately, returning these bristles to their original form is quick and easy. Just stick with this method, and you'll never have to throw away another brush due to crimped bristles.
Run hot tap water until it gets as hot as it will go, then fill up a glass or plastic container that is large enough to hold all of your damaged brushes.
Place all of the brushes that need straightening carefully into this bath. Make sure that all of the bristles are completely submerged. Allow them to soak for about 10 minutes.
Pull the brushes out of the bath and lie them on a flat surface. If you have multiple brushes, lie them in a row with all of the bristles pointing the same way and line up the metal bands at the bases of the bristles.
Lie the edge of a baking sheet over the bristles of all the brushes. Set heavy canned goods on the baking sheet directly over the brushes to add weight.
Wait for the brushes to dry completely. The bristles should all be straight and back in place.