Want to learn something new today?


We’ve been suspecting for the past week that the Fall weather may have arrived here on the Central Coast, bringing with it chilly mornings, crisp air, and the need for a few extra layers. We didn’t have any idea how cold it was until one of our cellar workers noticed some white crystals developing on his fingernails. Upon closer inspection the team realized that they were Tartrate Crystals!

What are Tartrate Crystals?

“Tartrates, affectionately known by industry professionals as “wine diamonds,” are tiny, crystalline deposits that occur in wines when potassium and tartaric acid, both naturally occurring products of grapes, bind together to form a crystal. Tartrates are scientifically known as potassium bitartrate, which is the same thing as cream of tartar used in cooking. They are completely harmless and natural. The formation of wine diamonds is less common in red wines, as their level of tartaric acid is lower, and crystals tend to fall out naturally during the longer barrel-aging process.” – Ronn Wiegand, Master of Wine/Master Sommelier

So why do Tartrates form and why were they on our crews fingers on the sorting line? Tartrates, by nature, are a normal byproduct of wine as it ages, but if the wine is exposed to temperatures below 40°F these crystalline structures will form as well. With the onset of the colder weather, more Tartrates have been forming on the machinery, fermentation tanks, hoses, as well as the crew’s fingers.

The next big questions are “how do you keep Tartrates from forming” and “do they have a negative effect on the wine?”


One technique that winemakers will use is a process called cold stabilization. What winemakers will do is cool the wine down anywhere from 28-40°F for a number of days just before bottling the wine. This process is purely for aesthetics in the hope that the wine diamonds won’t form later on down the road. Here at Foxen we cold stabilize our whites at 30-32°F for 2-3 weeks.

To answer the second question, no, Tartrates have no negative effect on the wine itself. Many would argue that the presence of Tartrates in older vintages is a sign of quality wine, indicating that the wine was not over processed. Another bonus is the crystals do not impose any flavor on the wine as well.

So everything on our end has been done to prevent the crystals from forming, what can you do at home? Store your wines in moderate temperatures ranging from 55-60°F and if serving a delicate white, chill it down to 45-48°F just before serving and avoid keeping them in a refrigerator that gets below 44°F.


Hope you enjoyed these fun facts, and now you can impress your friends and family the next time you come across these pretty, little wine diamonds.


One Comment on “Want to learn something new today?

  1. Pingback: Opus One Winery | Wine Life Radio

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