What is that stuff in my wine?

We are frequently asked, “What is that stuff in my wine?” What people are really asking is, what are the white or red crystals in my wine? 
Wine is made up of many different compounds and one of these compounds is acid. This acid comes primarily in two different forms: tartaric and malic with grapes having mostly tartaric. Tartaric acid can further be broken down into potassium bitartrate,  “cream of tartar”.   Because this acid does not completely dissolve in wine, even though initially it may appear to, it eventually crystallizes and begins falling out of the wine over time. Refrigeration can speed up this process. These crystals are naturally occurring and are not a fault in the wine.  
Crystals are more common in red wine where they are stained by the wine and are regarded as part of the sediment. These tartrate crystals are also formed as part of the aging process. Some wines are more susceptible than others due to the climate where they are made and the grape varieties used. German wines are often affected.
Because many consumers don't know the story of crystals in wine, most mass wine producers process the wine to precipitate and filter out the crystals. We also cold stabilize our wines to minimize crystals but too much processing also destroys complexity such as flavors and aromas in the wines. 
Don't shake the bottle and pour your wine gently and the crystals will stay in the bottle. Or you can decant the wine. Crystals mean your wines are real and made to be the best. Feel free to impress your wine friends with your new knowledge!