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Wine Diamonds,Not Sediment


A few patrons have approached us with questions about “wine diamonds” or “bitartrate crystals” in their wines.  Rest assured, this isn't sediment!  Rarely, in our high-end wines (Classic Select and above) crystals appear after aging in the bottle.  These are harmless, tasteless and actually, an indication of high quality.

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Wine Diamonds, Metatartaric Acid & Cold Stabilization

This article is for the benefit of the few of you who have approached us with questions about “wine diamonds” or “bitartrate crystals” in their wines.  Rarely, in our high-end wines (Classic Select and above) crystals appear after aging in the bottle.  These are harmless, tasteless and actually, an indication of high quality.  Here is a bit of information about this topic:

Grapes naturally contain several organic acids including tartaric acid. They also contain potassium and calcium ions which can form salts with these natural organic acids.  These salts can precipitate out of the wine to form a material called potassium (calcium) bitartrate. These are a clear (or sometimes red or brown) crystalline material. They are also referred to as wine diamonds", but vintners also call them "tartrates".  These bitartrate salts have several interesting physical properties:

In the unfermented grape juice, only a small quantity can be dissolved. 

Even less is soluble in the juice (wine) after fermentation, since alcohol can dissolve less of it.

The quantity of potassium bitartrate dissolved in wine is also strongly temperature dependent. Cold wine cannot hold as much bitartrate as warm wine, hence even more tartrates will drop out.

In combination, these three properties produce an interesting winemaking problem. Generally, grape juice contains all the bitartrate it can hold when the grapes are picked. Alcohol begins to accumulate when the grapes are fermented. As the alcohol concentration increases, the new wine becomes saturated, and tartrate precipitates out of the wine. As fermentation continues, more alcohol is produced, and more tartrate is forced to precipitate out of wine. By the end of fermentation, the new wine is over-saturated with tartrates and they can continues to drop out of the solution, at normal cellar temperatures, for a year or more.

As tartrate drops out of solution, suspicious looking crystals or dense sediments are formed in the bottle. Tartrate sediments are unsightly and are sometimes mistaken for glass particles, however, they are in no way harmful nor do they spoil the wine.

When a wine "kit" contains more fresh juice than concentrated juice, chances of acid instability is higher. So we regard a tartrate dropout more of a sign of quality than a problem or an issue.  The higher the level of juice in the batch of wine, the higher the likelihood of crystals.  That said, not all high-end wines will have "wine diamonds".  We find less than 5% of the high-end wines made at The Shoppe with "wine diamonds".

The easiest solution is the use of Metatartaric Acid already added to all our high-end wines. Metatartaric Acid will temporarily prevent the formation of crystals of potassium tartrate from saturated young wines. This is not a permanent solution, reaction depends on the storage period of the wine and on the storage temperature. It has been our experience at The Wine Shoppe on Charlotte and at RJ Spagnols (the supplier of our juices and concentrates) that these wines will be stable and free of wine diamonds for one year. However, if the wine is stored in cold temperatures (like in the refrigerator) it can cause wine diamonds to drop out before then.

If you are finding "wine diamonds" in your wine and it is over a year old or has been cellared at colder temperatures, there is nothing we can do to prevent it in the remaining bottles of your batch.  However, there is one thing you can try.  A coffee filter!  We simply place a coffee filter inside a funnel which is placed inside a carafe.  The filter will catch the crystals, and the wine in the carafe will be tartrate-free. Keep in mind, there is nothing harmful about the crystals but they can be a nuissance.  A lot of the time, the crystals will stay in the bottle when the wine is poured and then can simply be rinsed out of the bottle later.

If you have further questions please contact us!