Sodium bentoniteis a natural sealant. It swells 15-18 times its dry size when wetted by water and it is one of the “most effective low cost methods” of treating porous soils. uses: drilling mud, purification, binder, absorbent, Groundwater barrier, Pottery, sealing stock and recreational ponds, dairy and sewage lagoons and city landfills. It is also effective as a hole plug as well as for controlling dust on highways.