Use Madelaine's Propylene Glycol Solution with any foam or crystal cigar humidifier to make it perform flawlessly. Madelaine's Solution will automatically regulate the humidity in your humidor at 70% ensuring a humidor fresh smoke every time. It will also inhibit mold growth. Best of all, Madelaine's "Use Every Time" formula takes all the guesswork out of using PG solution. Simply use it every single time you need to refill your humidifier.