Metatartaric acid
A cheap, temporary block on tartrate crystallisation.
Typical dose
Around 100 mg/L, at bottling.
When to add it
At bottling, on a wine that will be drunk within a year or two.
In practice
Coats the growing faces of potassium bitartrate crystals so they cannot form, sidestepping cold stabilisation entirely. The catch is that it hydrolyses and stops working within months, faster if the wine is stored warm, so it only suits a wine that will be drunk young.
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
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.
Bitartrate seeding
Seeds cold stabilisation so tartrate drops faster and more completely.