Kitchen sponges and wash cloths are notorious for attracting and breeding mold and bacteria. They are used to clean up spills of all kinds and then are usually left wet until the next use. This creates a perfect breeding ground for all kinds of nastiness. To disinfect your sponges, saturate with clean water and microwave for two minutes. This will kill any organism that has made its home in your sponge. Carefully remove it from the microwave and rinse with clean water. To maintain a clean sponge always rinse thoroughly after use and allow to dry completely on a clean dish rack.
