Precipitated chalk (also known as calcium carbonate or acid reducing powder) is used to reduce acidity (raise the pH) in wines (or other brews eg beer) that are too acidic. 60g pack.
Start by dissolving 1/2 teaspoon per 5 litres in a small portion of the must and then mix the treated portion back into the wine.
Retest (or retaste) and add more if necessary.
LIMIT of 3 without prior arrangement. Stock can be ordered in especially, lead time about a month. Email info at makewine dot co dot nz