Tartrate is a crystal formed when Tartaric Acid reacts with Potassium as the temperature of a wine cools.
Also known as Wine Diamonds, Tartrate is harmless, settles quickly to the bottom of the bottle and can be removed by simply decanting.
Tartrate in it’s pure form is also known as Cream of Tartar. It is used in baking, and, is an ingredient in baking powder. You guessed it, they source the tartrate from the wine industry!
Both Tartaric Acid and Potassium are naturally present in grapes. The solubility of Tartaric Acid and Potassium is dependant on temperature, alcohol concentration, pH and a number of other factors.
Commercial wines are typically made cold stable by chilling the wine down to close to 0ºC encourage tartrate crystallisation, the crystals are then removed by filtering or natural sedimentation followed by racking the wine. There are a number of other methods to achieve this result.
It’s common to see Tartrate in wines that have high acidity, Sauternes, German & Alsatian Riesling, Nebbiolo and many others.
Below is a picture of tartrate from the bottom of the tank when we racked the 2017 Shiraz after it’s second winter cooling in 2018. You can see it’s picked up a bit of colour too.
The cork of a 30 year old Botrytis Riesling with tartrate crystals on it.
The Chemistry
The decanter after a 2013 Sandrone Barbera was polished off. Barbera has very high natural acidity and is prone to forming tartrate in the bottle.
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