Bentonite is a natural clay mineral with the same chemical constituents as other clays, but with a unique molecular structure that permits it to absorb many times its weight in water. Upon absorption bentonite will swell enormously up to 15 times its normal bulk weight. Once in such a saturated state the absorption is still reversible and bentonite can be dried out and eligible for reswelling again. Bentonite’s thirst for water and swelling are its strengths in stopping the passage of water. Under confined conditions, such as a buried mixed blanket, the wet and therefore swelled bentonite particles will be jammed against each other and into voids between soil particles to form a barrier against further passage of water and fluids. Bentonite is self sealing with an unusual flexibility that permits the movement of bentonite particles while simultaneously not breaking the water barrier seal.