Carpet shampoo is one method that uses soap to creates lots of foam. When using this method we will apply a layer of thick foam to the carpet, which upon drying will attract the dirt and soil from down in the carpet. When the foam completely dries, it can be vacuumed up along with the dirt the next day. The foam is applied with either a cylindrical foam machine or a rotary shampoo machine. Either of these machines will accomplish the same end result, clean carpet.