Wine fault
Tartrate crystals
Harmless clear or coloured crystals that look like glass or sugar. Not a fault, and often a sign of gentle winemaking.
Completely. Potassium bitartrate is an ordinary food ingredient — the same substance as cream of tartar.
What you notice
Appearance
- Clear, glassy crystals in the bottom of the bottle or stuck to the cork
- Reddish or purple crystals in a red wine
What it is
This is the most frequently misdiagnosed thing in wine. The crystals look alarming — like glass, or broken sugar — and they are completely harmless.
Tartaric acid occurs naturally in grapes. Cold makes its potassium salt precipitate, which is all that has happened.
Many producers cold-stabilise wine specifically to force this out before bottling, purely so consumers do not see it. Some now choose not to, on the grounds that the process can strip aromatics — so crystals can actually indicate a gentler approach.
They are sometimes marketed as "wine diamonds", which is a fair description of what they look like.
What causes it
- Potassium bitartrate — the same compound sold as cream of tartar — becoming less soluble at low temperatures and precipitating out.
- Storing a bottle somewhere cold, including a domestic fridge.
- Wine that has not been cold-stabilised before bottling, which is an increasingly common deliberate choice.
Can I fix it?
Nothing to fix
There is nothing to fix. They are harmless crystallised tartaric acid, and their presence often means the wine was handled gently.
What you can do
- Nothing. Drink the wine.
- If the crystals bother you, decant the wine off them or pour carefully.
- They will not dissolve back in and they do not affect the taste.
What does not work
Published because a reader holding a spoiled bottle has usually already been told to try one of these. Correcting the specific wrong advice is more use than stating the right answer beside it in silence.
- Trying to dissolve them by warming the bottle
- They will not go back into solution at any temperature you would want to serve the wine at, and warming it does the wine no good.
Is it safe to drink?
Not a safety problem
Unpleasant, not harmful. You can drink it; you may not want to.
Completely. Potassium bitartrate is an ordinary food ingredient — the same substance as cream of tartar.
Can I take it back?
No. This is not a fault, and a knowledgeable retailer will explain the same thing.
Sources
Sources consulted
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