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

Ask Dr Vinny

Hello there! I'm Dr. Vinifera, but you can call me Vinny. Ask me your toughest wine questions, from the fine points of etiquette to the science of winemaking. And don't worry, I'm no wine snob—you can also ask me those "dumb questions" you're too embarrased to ask your wine geek friends! I hope you find my answers educational, empowering and even amusing. And don't forget to check out my most asked questions and my full archives for all my Q&A classics.

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

Ask Dr. Vinny Winemaking Techniques Explained

More In Dr. Vinny

What does it mean to say a wine is "full-bodied"?

Wine Spectator's expert Dr. Vinny explains how we talk about a wine's structure and "body."

Nov 1, 2021

Is it OK to store wine in Styrofoam shipping containers?

Wine Spectator's resident wine expert, Dr. Vinny, explains the pros and cons of storing …

Oct 25, 2021

What are biodynamic wine grapes?

Wine Spectator's expert Dr. Vinny explains some of the farming principles applied to …

Oct 18, 2021

How does leftover wine change after a few days?

Wine Spectator's expert Dr. Vinny explains what happens to wine after it's opened, and how …

Oct 11, 2021

Are you supposed to put the capsule back on an unfinished bottle of wine?

Wine Spectator's expert Dr. Vinny explains why wine capsules have little holes (they're not …

Oct 4, 2021

What’s the difference between organically grown and organically made wine?

Wine Spectator's expert Dr. Vinny explains what it means when you see the word "organic" on …

Sep 28, 2021