Calcium Carbonate (CaCO3), also known as lime, is used to raise pH levels in the mash. It is generally for making darker beers. Brewers normally add sparingly calcium carbonate to lower acid in beer. Acid reduction occurs immediately. Limited solubility makes it only effective when added directly to the mash. Calcium Carbonate increases the pH, water hardness and alkalinity. Carbonate functions as a buffering agent against mash acidity, neutralizing the higher acid content of dark roasted malts.