When the formula lather is rinsed out of the sponge, your sponge is clean but it’s important to let your sponge air dry after every use and not leave them inside the cleansing jar. Additionally, these reusable sponges can be washed with laundry in a washing machine. We recommend washing them along with towels and letting them air dry. If you need replacements, we sell sponges individually on the website! (Recommended time of use in between washes is two weeks.)