The term calcium bentonite clay does't specify what kind of clay it is or what it's quality is. Some clays have little benefit when used for metal cleansing. Others are so polluted, they make matters worse. You may need t odo your own research. I usually recommend Pascalite clay because I know where it is coming from and that is is very effective. One pound of clay per bath is sufficient. Soak in the bath for half hour, not more. You may mix some clay with a little water and apply to neck, face and head. Rinse or shampoo afterwards.

best wishes,
Andreas