Gypsum, or calcium sulfate, is used to correct mineral deficiencies in water which is to be used for brewing. It is used in purified or soft-medium hard water to increase permanent hardness. Gypsum helps establish proper pH and provide sufficient calcium ions essential for enzyme function, kettle protein coagulation and yeast metabolism. Use 1 - 2 teaspoons per 5 gallons. 2 oz. container.