Bitartrate seeding
cream of tartar, KHT contact process
Seeds cold stabilisation so tartrate drops faster and more completely.
Typical dose
Around 4 g/L of cream of tartar stirred into cold wine as seed crystals.
When to add it
During cold stabilisation, near freezing.
In practice
Adding fine bitartrate crystals to a chilled wine gives the dissolved tartrate a surface to grow on, so it precipitates in days rather than weeks and far more completely. It is the industrial contact process in home form: chill, seed, stir, then rack off and, ideally, filter cold. The seed itself is food-grade cream of tartar.
Linked faults are the ones this addition either treats or, used wrongly, causes. The fault page says which, and whether it can be undone.
Others in tartrate and colloidal stabilisers
Metatartaric acid
A cheap, temporary block on tartrate crystallisation.
Carboxymethylcellulose
A durable tartrate stabiliser for whites and sparkling.
Mannoproteins
Yeast-derived colloids that steady tartrate and protein and add texture.
Potassium polyaspartate
A newer tartrate stabiliser that also works in red wine.