Ever drink a glass of really good wine and find little crystals at the bottom? These are “wine diamonds,” not sediment, and they have been helping to preserve your wine!
Wine diamonds are, in actuality, potassium bitartrate crystals that sometimes form on a wine bottle’s cork, most often when chilled. During the winemaking process, itself, they naturally form on the sides of fermentation tanks. They can be found in both red and white wines, and do not in any way mean that there’s a problem with your wine. In fact, when present, they help lower the pH, making a hostile environment for many types of bacteria that can spoil wine, helping to preserve wine after fermentation.
The majority of winemakers, however, have gone to great lengths to eliminate these crystals from their bottles. (Mostly, this is a reaction to complaints about the harmless crystals.) Very cold stabilization before bottling (usually between 2 or 3 weeks) is a “solution” that brings these tartrate crystals to the fore, allowing them to be easily filtered from the wine which is then warmed back up.
If you do find wine diamonds in your wine, your wine was probably made very naturally, and this is a good thing! Also note that consuming the crystals will not harm you; these wine tartrate crystals are the very same ingredient in the cream of tartar you used for baking the other day. They’re also used in a bunch of other foods and nonalcoholic drinks. It so happens that wineries are the only commercial sources for tartrates, and they often collect and sell wine diamond deposits that form in their tanks.
So, the next time you see a few crystals at the bottom of your wine glass, know that they have occurred naturally, are nontoxic, and that they have helped to preserve your wine. Cheers!