Bentonite is a moisture retaining clay used as an earth electrode back-fill to help lower soil resistivity. The clay is a sodium activated montmorillonite, which when mixed with water swells to many times its original dry volume. While there is no specific mixing ratio, we recommend gradually adding Wallis Bentonite to water in a mixing vessel, agitate to evenly disperse the Bentonite and continue mixing until there is a workable slurry that suits the site, hole or trench.