Calcium carbonate is used to reduce the acidity of 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.
Calcium carbonate is also used in beer to increase the temporary hardness of water. Traditionally used in English stouts, pale ales and bitters.