Have you ever wondered about the little glass-like crystals clinging to the cork or collecting at the bottom of a bottle of wine? These “wine diamonds” are called tartrate crystals, natural particulates that form during and after the winemaking process when the wine drops to a cold temperature. The crystals form when two naturally occurring elements found in wine, tartaric acid and potassium meet under cold temperatures and bind together to form potassium bitartrate, which is essentially a salt. This is why you might find that crystals form in a white wine once you put it in the refrigerator.
Wines are often clarified and stabilized before bottling to remove small particles of yeast, tannin, and other grape matter prior to bottling. Among these processes are filtering, fining and cold stabilization (essentially refrigerating the wine) to help clarify the wine prior to bottling. These processes help prevent the formation of tartrate crystals, which form when the correct elements and cold temperatures are present together in the wine.
Because we do not clarify our wines prior to bottling, it is common to see tartrate crystals form in our Chiara Bianco and Chiara Rosé of Zinfandel, especially once you put it in the refrigerator. The most important thing to know: they are harmless! Tartrate crystals have no impact on the flavor or quality of the wine. By not filtering or fining our wine before bottling, the result is a more aromatic, textured wine that has weight and a beautiful finish.