A sponge that can dry completely between uses does not hold bacteria. Most kitchen sponges are made of foam, such as polyurethane. The sponge's inner surface is extremely large due to the porous structure. This offers microorganisms plenty of room to grow. Our upcycling Fischnetz dish sponges are not porous and do not soak water. Air can flow through their diamond mesh structure which makes them dry quickly. They do not act as a reservoir of microorganisms and do not hold bacteria.