You only need to use the Pascalite clay once or twice every year or two (1 bottle each = 16 ounces). You soak in the bath for about 30 minutes. Keep moving the water to maintain a good degree of saturation. When finished let the bath water sit for a while before draining, then you will see the black sediments. There are other good clays out there, but I found this one to be very effective and inexpensive.