Calcium Carbonate (Precipitated Chalk)

Used in wine to reduce the acidity of grape or fruit wines, and in beer to add a temporary hardness (generally to reduce the mash pH of dark beers).

To use, dissolve 1/2 teaspoon per 5 litres in a small portion of the must and then mix the treated portion back into the wine.  Never add more than 50 g in 23 litres of wine.