05/20/2026
Over the years we have heard the question... What are the crystals that collect on the corks in our red wines? Here is your answer directly from our winemaker Bob Bolan.
The crystalline deposit you sometimes see on wine corks is potassium bitartrate (AKA cream of tartar). The predominant acid in grapes and wine is tartaric acid. Over time under cool storage conditions, some of the tartaric acid can precipitate out of solution to form crystals. We store our wines upside down to keep the corks wet, which is why these crystals accumulate on the bottom of the corks.
Large wineries force the precipitation of excess tartaric acid prior to bottling in a process called cold stabilization, whereas smaller, boutique wineries are more likely to allow wine aging to take a more natural course. As a result, some people view the presence of these crystals as a sign of quality. At any rate, they are a natural byproduct of wine aging and are perfectly harmless.
The crystals do taste bitter, however; so if there are residual crystals in the neck of the bottle after pulling the cork, I either remove them with a tissue or splash a little wine into the sink before serving the wine.
Cheers!
Bob
