Dirll 20 to 25 1/8-inch holes in the bottom of your pail with a power drill.
Take soil from the area where you intend to apply the sodium bentonite and fill 3 inches of the pail. This will represent 1 square foot of the total area you intend to place the sodium bentonite over.
Measure 1 to 2 pounds of sodium bentonite and place it over the soil in the pail.
Pat the sodium bentonite down so that it is firm.
Lift the pail up and see if the water is leaking out of the bottom. If it is, increase the amount of sodium bentonite by 1/2 pound until the leaks stop.
When they do stop, use this ratio to determine how much sodium bentonite you apply to the total per-square-foot surface area.