🥃 Wine diamonds (tartrates)

Wine diamonds, or tartrates, are small crystals that sometimes appear at the bottom of a bottle or on the cork. They are harmless and do not spoil the taste.

The crystals are made of a salt of tartaric acid, potassium bitartrate. Tartaric acid occurs naturally in grapes. When wine sits in the cold, the salt drops out as a deposit. The colder it is, the faster this happens.

Many winemakers do not wait and remove the crystals in advance. They chill the wine and the salt settles in the tank. This is called cold stabilisation. The bottle then looks cleaner, though the quality of the wine does not change.

Tartrates are like other grape by-products, such as pomace and lees: they also stay at the bottom of the tank. Tartaric acid is obtained from them, and in the kitchen they are known as "cream of tartar", a raising agent for dough.

If you see shiny grains in your glass, they are not glass or salt, just traces of the wine.