I’ve been thinking about the pH drop that brought fermentation to a near halt, and I’ve decided to deacidify with potassium bicarbonate (KHCO3). Most of the information I could find on neutralizing acid has to do with reducing the total acidity (TA); I couldn’t find anything about deliberately raising the pH. That means I have no clear guide in deciding how much KHCO3 to add. When I last measured the TA, it was 6 g/L. I’ve arbitrarily decided to neutralize half of it. To reduce the acidity by 1 g/L, you need to add 0.9 g/L of KHCO3. Since I’ve got a gallon (3.785 L) of wine and I want to neutralize 3 g/L of acidity, I need to add 10.2 g KHCO3 (0.9 * 3.785 * 3). I haven’t got a scale accurate enough to measure out 10.2 grams of anything, but a teaspoon of KHCO3 is about 4.8 g so adding two teaspoons (about 9.6 g) gets me pretty darn close to 10.2 g.

So what happens when I add the KHCO3? It combines with the tartaric acid to form potassium bitartrate (cream of tartar), carbon dioxide, and water. The cream of tartar precipitates out and the CO2 bubbles off leaving a tiny bit of water. That should leave the wine with a high enough pH to kick start the fermentation. I’ve ordered the KHCO3, it will arrive in a few days, and then we’ll see if there’s method to my madness.

Most of the info on neutralizing acid came from Philip Jackisch’s Modern Winemaking. It’s a good book that provides technical detail on winemaking processes with examples. It’s for the winemaker looking to go beyond the basics, and I highly recommend it. There’s even has a chapter on non-grape wines!

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