Styrofoam is used an an insulator and a packing material, as well as in many other household applications. Styrofoam is prone to mildewing, and can mold in some situations. In addition, storage can allow dirt and dust to build up on styrofoam, making cleaning necessary. Because of the physical and chemical properties of styrofoam, though, you need to be very careful what chemicals are used to clean it. Some chemicals act as solvents on styrofoam, and can damage or dissolve the material. Use only regular dish soap to clean styrofoam.
Place a garden hose into a bucket, and turn on the water.
Squeeze three to five drops of dishwashing detergent into the stream of water as the bucket fills.
Turn off the water when the bucket is approximately 3/4 full.
Dip the soft sponge in the bucket until wet, then gently clean the styrofoam until clean.
Rinse out the sponge using the hose, and rinse the soap from the styrofoam using the sponge.
Spread the towel on the ground or a table in the sun. Place the styrofoam on the towel to dry.
Allow the styrofoam to sit in the sun for two to three hours to completely dry.