Tartaric Crystals in Wine: the "Wine Diamonds" quality

Have you ever come across what appears to be white flakes floating in your wine bottle? Did you assume that this snow globe appearance somehow meant the wine was defective or spoiled?

What you’ve probably seen are tartar crystals, commonly known as “wine diamonds” or Weinstein (“wine stone”) in German-speaking countries. So do these wine diamonds indicate a bad bottle of wine?

Opinions on this subject are divided and the reason is simple: you have bought an impeccable wine, but you have not bought an aesthetically impeccable wine. Depending on where you are from, this may matter more or less to you.

The American wine drinker is not used to finding wine diamonds on their bottles. Here, most wines undergo a cold stabilization process, which is when a wine is chilled before bottling so that the white flakes, called crystallized tartaric acid, “fall off” and can be separated from the wine. But at what price beauty? Cold stabilization influences the balance and flavor of a wine: as some winemakers say, the wine is actually breaking down, and rapid chilling changes the colloidal structure of the wine. One could call it a clear case of style over substance.

There is another interesting correlation between wine pits and the quality of a wine: the longer the grapes hang on the vine (colloquially called “hang time”), the more acid from the wine will accumulate in the grape, and it is this acid from the came the one that was the building block of the wine diamonds. Also, the longer the wine is allowed to ferment, the fewer wine diamonds will fall off during fermentation, but more will accumulate later in the bottle.

In other words, wine diamonds are an indicator that the grapes matured for a long time and that the winemaker slowly and carefully fermented the wine. Both are important precursors of high-quality winemaking.

Hans Gsellmann, head winemaker at the famous Gsellmann & Gsellmann winery in Austria, explains it this way: “Part of the acid in the grapes is tartrates, also known as salt. As the wine matures, these tartaric acid crystals they fall. It is a natural process that a wine will work its way to the peak of its production. When you see these flakes on the bottom of the bottle or on the cork, you can be almost sure that you are opening the wine at the right time. You should consider yourself lucky.”

Wine aficionados in the Old World have been known to look to bottles with wine stones as a sign of quality: it shows that the wine has not been stripped of its structure through unnatural cooling, and is a sign of a wine well matured. Perhaps it is due to the long history of wine making in these countries that people have grown accustomed to wine stones and seem to accept them. At least they seem to know that, if anything, the wine diamonds will have added roundness to the wine by taking away some of the acid.

There’s a new technology coming out of France that promises to circumvent the whole colloidal problem: electrodialysis. But until every notable winery has bought one of these fancy French machines (and that will certainly be a few decades), this general rule of thumb applies: cold stabilization is like throwing out the baby with the bathwater. Perhaps you are left with an aesthetically impeccable wine, but you are also left with a lesser wine.