Cream of Tartar

[Cellar_Rat]

Can you use Cream of Tartar to reduce your tartaric acid load even after cold stabilisation?

The acid in still quite high in my Seyval and I am running out of sugar. to mask it.

I have thought it would (should) produce some great vinegar though..

[NorthernWiner]

No. Cream of tartar (potassium bitartrate) is a byproduct of cold stabilisation and on its own doesn't reduce tartaric acid. Its only use in winemaking is for "seeding" a wine with tartrate crystals to encourage precipitation during cold stabilisation.

If you ever made rock candy as a child, it's the same principle. You start with a super saturated sugar solution, but crystals don't start to grow until you suspend a string in the solution. The string has a rough surface (microscopically speaking) which provides nucleation points for sugar crystals to take hold and grow.

In cold stabilsation the wine is saturated with tartaric acid, which is unstable at cold temperatures. To encourage the bitartrate crystals to grow large and heavy enough to drop out of solution, they need a foundation to build on. By seeding the wine with cream of tartar, you are providing that foundation.

It's also worth noting that the wine industry is the source for most of the cream of tartar you see sold in grocery stores.

[NorthernWiner]

To reduce acid in your Seyval, you may want to try potassium bicarbonate (not to be confused with bitartrate). 4 grams per gallon will reduce acidity by 0.1%. But don't aim for any more than about a 0.3% reduction, or it can screw up the pH and cause metallic off-flavors.

[SiSandrine]

It might be blasphemy but where I have had over acid pure grape wine in the past (quite common with UK grapes) I brew up a quick WN1 with very little acid and blend it to good effect. Some would argue it loses varietal character and this is true to an extent but I find that overpoweringly acid wines are worse. I would also only advocate blending a sufficient amount to bring the acid down to a preferred level for your taste.
A WN1 can be ready for blending in as little as 30 days so timing is not normally an issue (for me that is).