Cold Stabilization
From Distillers Wiki
The process of removing excess potassium and tartaric acid under chilled conditions as Potassium Bitartrate to prevent its precipitation in the bottle when chilled.
The purpose behind cold stabilization is to remove all tartrate crystals from a wine during its fermentation stage. Tartrate Crystals are also called "wine diamonds". They are a natural product of the wine, and form when the wine gets too cold. It is in essence cream of tartar, forming because of the temperature change. Think of sugar turning into rock candy and you'll have a good mental image.
Usually the main stainless steel fermentation vessel for the wine has a cooling system on it. After the fermentation is complete, that vessel is plunged to near-freezing for 3 to 4 days to force the crystals to form. The crystals stick to the sides of the vessel, and when the wine is then removed, the crystals remain behind. Some winemakers argue that a portion of the flavor and uniqueness of the wine remains behind as well.
Cold Stabilization is normally only done to white and blush wines. This isn't because red wines do not form crystals - any wine will form crystals, since every wine is made from grapes containing the ingredients for crystals. However, since crystals only form when a wine gets very cold, red wines rarely show crystals, since red wines are served at a relatively warm temperature. They should never reach that cooler, crystal-forming temperature.
