Log In / Join Now

Ask Dr. Vinny

Do you have a question for Dr. Vinny? Ask it here...

Dear Dr. Vinny,

I found what appear to be chunks of glass in a bottle of wine. There was no apparent breakage of the bottle itself, and my friend and I carefully inspected it once the glass pieces poured out. Could it have occurred during bottling?

—Amanda P.

Dear Amanda,

I haven’t inspected the chunks personally, but my guess is that it was something much less scary—tartrate crystals, which are harmless and a natural occurrence with wine. Sometimes they look like rock candy, sometimes they cling to a cork, and sometimes they look like shards of glass. Odorless and tasteless, they’re just crunchy crystals. I’ve heard them referred to as "wine diamonds," which is sweet and romantic. Who doesn’t want diamonds made of wine?

Tartaric acid is one of the acids found in wine grapes, and it tends to settle out of wine during fermentation and aging. It’s also sensitive to cold temperatures, and when a wine is chilled down, the tartaric acid can drop out of the wine and not dissolve again. Some wines actually go through a cold stabilization process to separate the tartrate crystals before the wines are bottled, purely for cosmetic reasons (and to make sure your wine isn’t crunchy).

If it helps, these crystals are also made from the same stuff that cream of tartar is (most cream of tartar is actually harvested from wine barrels). It’s what keeps my snickerdoodle cookies nice and airy.

—Dr. Vinny

Wine Basics

We break down the basics—how to taste, serve, store and more. Plus:
» Maps of major wine regions
» Grape variety characteristics

How-to Videos

Learn to taste wine like a pro, pull a cork with flair, get great wine service in a restaurant and more

Wine Spectator School: All courses are FREE for WineSpectator.com Members

Learn from the experts and get the most out of each sip. Take one of our online courses or take them all—from the ABCs of Tasting to in-depth seminars on Food Pairing, California Cabernet, Bordeaux, Tuscany, Sensory Evaluation and more.

Browse our course catalog
Check out the professional wine sales and service courses
Learn Wine Forum: Got questions? Get answers

WineRatings+ app: Download now for 340,000+ ratings.