Cold Stabilization (Day 100 - 105)
After your wine has been sweetened, stabilized, degassed and your clearning agent has been added you can now put your wine through a process called cold stabilization. Not everyone uses this step, however, I find using it makes for a much more clear wine. (Note: Don't use this step if your TA is low as it can cause your TA to drop)
The purpose behind cold stabilization is to decrease your acid levels by removing 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.
Tartaric acid is a normal grape acid. Potassium also exists in grapes, and when these two things bind together under cold conditions, they form little potassium bitartrate crystals, which then settle to the bottom of the bottle. They're completely harmless, and quite natural. The problem, of course, is with appearances.
While in Europe these crystals are accepted as a sign that the wine is a natural one, and even appreciated, North Americans are used to wine being clear, pure, filtered, processed and de-sedimented. Consumers often panic when they see little crystals in their Chardonnay, thinking they are impurities or even bits of broken glass. Cold Stabilization is a way to prevent these crystals from forming.
In order to cold stabilize your wine you will need a place where the temperature is around 0-5 degrees Celsius. (This may be found in your cold cellar during winter months or, if you’re lucky enough an empty fridge). Place your carboy into this area and wait for 10 days. During this time the compounds will bind and the tartaric acid will crystallize and precipitate to the bottom of the carboy.
After 10 days you are now ready to move on to the next stage.
Note: If you do not have the facilities to process the cold stabilization phase, don’t worry about it. As mentioned before, this process is only making your wine more presentable, and not better tasting. If you chose to not do cold stabilization, you must still put your wine through a 10 day resting period before moving on to the next phase.