Dissolve the Barrel-Kleen into 1 U.S. gallon (3.8 L) of warm water. Fill the barrel with this cleaning solution and soak for 24 hours. Empty the barrel and rinse three times with hot water. Dissolve the neutralizing acid into 1 gallon of warm water. Fill the barrel with this neutralizing solution and soak for 15 minutes. Empty the barrel and rinse three times with hot water. To re-char the interior of the barrel, drain the barrel for 3 hours, and place a butane torch through the bung hole. Rinse the barrel with warm water. Dissolve the two (2) sterilizing tablets into 1 gallon of cool water and fill the barrel with this sterilizing solution. To re-use the barrel, drain and triple rinse with cool water. To prevent barrels from drying out and to minimize contamination, barrels should always be stored full with spirits or a sterilizing solution. Unused portions of solutions may be stored for up to 2 months. 1oz Citric Acid 1oz Barrel Kleen 2 Campden Tablets.