Today’s microwaves range from small to extremely large and powerful. While a mid-sized microwave might sanitize your sponge perfectly at 2 minutes, a smaller one may fail to kill all the bacteria. And even worse – a stronger microwave can dry your sponge enough to set it on fire.
When your sponge starts to get dirty, soak it for five minutes in a bowl of water with three tablespoons of bleach. Rinse thoroughly after the five minutes. Or even better – buy your sponges in bulk and toss the old ones as needed. Happy cleaning!