First, let's deal with tartrate crystals. They are formed when a method called cold stabilization is performed on a wine. Cold stabilization is often done in white wines to remove excess potassium bitartrate, a natural substance found in grapes also known as "cream of tartar." White grapes contain fairly large amounts of potassium bitartrate. If most of it is not removed, the wine will form crystals when placed in the refrigerator. These tartrate crystals will either cling to the underside of the cork, if the bottle is on its side, or fall to the bottom of the bottle, if it's standing up, where they appear to be ground glass to the uneducated eye
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it's totally harmless