Dear Wine Wizard,
I have had two five-gallon carboys in my garage at temperatures ranging from the teens to 40° F for 3 weeks. Is this long enough for the tartrates to crystallize and settle out? I am asking because in the past, I have left the wine in the basement for several months at temperatures no lower than 46° F and I still noticed tartrate crystals.
Wine Wizard replies: Sometimes commercial wineries chill their for months in the 30-degree Fahrenheit range and still get "tartrate fallout." Even if a wine has been "cold stabilized," as this process is called, there’s no guarantee that it won’t throw some crystals (and other sediment) as it ages.
The variables that determine how many tartrate crystals a wine will throw in its lifetime are multifold and hard to fully understand. In wines with high tartaric acid content, low temperature and high ethanol content, you’ll generally see more tartrates falling out over a long period of time. This means that the potassium bitartrate is not soluble in the wine. Since time and temperature are the two easiest parameters to control for the home winemaker, storing a wine at the lowest temperature possible (above the freezing point) for as long as possible (say, a month), will force out the greatest amount of crystals. Follow this cold stabilization by siphoning the wine off the sediment and you’ll be able to bottle a wine that will throw a minimum of sediment in the future.
Many winemakers use an old chest freezer as their "cold stabilizer" and pop jugs and carboys into it for a month or so at about 35° F. However, there is no "magic number" when it comes to cold stabilization. Every wine is different and everyone plays with the time and temperature parameters according to their individual equipment and situation.
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