Wine Diamonds A Little Sparkle in Your Glass

Every now and then, a bottle of wine hides a small surprise. Tiny crystals may appear at the bottom of the bottle or on the cork, catching the light like scattered gems. These are wine diamonds, and they are a natural part of wine’s story.

Wine diamonds are tartrate crystals that can form in wine. Tartaric acid naturally occurs in grapes and wine, but winemakers may also add tartaric acid during production to adjust the wine’s acidity. When this acid comes together with minerals such as potassium or calcium, crystals can eventually form.

Most wine diamonds are potassium bitartrate. These crystals are particularly affected by temperature, which is why wineries may cold stabilise wine before bottling. Cooling the wine encourages the crystals to form and settle out before the wine reaches the bottle. Calcium tartrate is a little different. It is less affected by temperature and can take much longer to form, meaning crystals can sometimes appear months after a wine has been bottled.

White and rosé wines tend to show wine diamonds more often because they are usually served chilled. They may look unusual, but there is no need to worry. Tartrate crystals are harmless, tasteless and do not affect the quality or flavour of the wine.

There are other ways of helping to prevent wine diamonds too. CMC, or carboxymethylcellulose, can be used to help stop potassium tartrate crystals from forming. Rather than removing the crystals, it works by making it harder for them to develop.

Some wineries choose to remove tartrate crystals before bottling, while others are happy to leave them. If you happen to find a little sparkle in your glass, there is no need to worry. Just enjoy the wine and its quiet bit of magic.