I think there's broken glass inside my wine bottle. How did that happen?

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Dear Dr. Vinny,

I saw a piece of broken glass at the bottom of a fresh glass of wine, but the bottle seems intact. How could broken glass have gotten into the bottle?

—Daljit, New Delhi, India

Dear Daljit,

I’m guessing that it was not broken glass that you saw, but actually a harmless and naturally occurring tartrate crystal. Sometimes they look like big chunks of salt or rock candy, and they can collect on corks or you might see them at the bottom of a bottle of wine.

These crystals are a natural byproduct of winemaking. Grapes contain tartaric acid, which precipitates out of solution in the form of tartrate crystals. These crystals are most likely to form when the wine gets cold, so some winemakers use a cold stabilization process before bottling so that they can ensure the crystals don’t end up forming in the bottle.

Tartrate crystals can be unpleasant to crunch down on, but they’re perfectly harmless. They are sometimes referred to as “wine diamonds,” a lovely way to try to convince people not to worry about them. Another way to consider their harmless nature is to remember that they’re the same substance used to make cream of tartar, which keeps my snickerdoodle cookies light and airy.

—Dr. Vinny

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