Using bentonite to create a soil liner. VOLCLAY bentonite soil sealants are granular and powder sodium bentonite that provides economical, low permeability soil liners for a wide variety of containment applications. When VOLCLAY bentonite soil sealants are mixed with soil and hydrated, they expand to fifteen times in volume, forming a mechanical bond with surrounding soils and filling the voids between the soil particles. This creates a barrier that effectively stops further seepage through the soil, and decreases the permeability of soil by several orders of magnitude. Bentonite can withstand desiccation, hydration and freeze-thaw cycling without losing its sealing ability.