It wasn't until I purchased my first professional-quality makeup brush set that I first heard the word ferrule. "Make sure you take care of your ferrules," said the saleslady. Say what? That's when I got my lesson in the anatomy of a makeup brush. There are three parts to the brush: the hair; the handle; and the ferrule — aka the metal part that holds it all together.
To keep your brushes from falling apart, take great care to prevent water from settling into the ferrule, as water can cause the glue to loosen in the brush's internal structure, which can lead to a broken brush. To keep your brushes happy, hold the hairs of the brush downward toward the flow of water while washing, so that the H2O trickles away from the ferrule. Once you've finished cleansing your brushes, lightly squeeze off the water with your fingers and lay the brushes flat on a clean towel. Tip: Allow the ends of the brushes to overhang to allow for faster, more complete drying.