Calcium carbonate is used in beer to increase the temporary hardness of water and to reduce the acidity of wine.
For Beer: Traditionally used in English stouts, pale ales and bitters.
For Wine: It does not require cold-stabilization to force complete precipitation, as does potassium carbonate. However, calcium carbonate is more likely to affect the flavor than potassium carbonate, and may take a few months to fully precipitate. One-quarter ounce (about 4 teaspoons) of calcium carbonate reduces acidity in one gallon by about 0.25%. Foaming may occur because of the production of CO2. Do not use more than one ounce per gallon. Wait 24 hours and rack wine.