Polishing Corn Cob & Walnut Shell Media "Re-Charger" is added to pre-treated polishing corn cob or walnut shell tumbling media every 40-60 hours of use to maintain the products polishing abilities. 1/2 lb of "Re-Charger" treats 1 cubic foot of media. Allow the re-charging powder to mix into the corn cob or walnut shell for 1 hour before adding parts for polishing.