March 28, 2012

Wine Diamonds :: Corked wine or Flawed perception

Not long ago, at an upscale dining establishment on the outskirts of AuroraOntario, my wife and I were sitting together at a table in the corner enjoying a lovely bottle of Chianti with our bruschetta and pasta entrées.  Joia Ristorante is a great place to eat, and I think that perhaps we both feel a few years younger than we really are as we sit amongst the hustle and bustle of the waite staff watching people come and go.  But it’s fun to get dressed up, ditch the kids and hit the town for a great meal paired with a good bottle of wine. 

At the table adjacent to ours, a couple were engaged in a rather heated discussion with the waiter. Apparently, there were ‘bits of hard stuff’ stuck to the bottom of the cork from the bottle he had opened for them only moments before.  From my vantage-point, I was unable to identify the label on the bottle but judging by the body language and ensuing performance, it was clearly a finer choice on the wine list, which incidentally, one might mistake for an old leather-bound bible.  Within the coveted document, patrons are presented with a plethora of very fine (and expensive) choices.  But expensive wine also comes with an elevated expectation, which is perfectly acceptable – if you know what to look for.  Let’s put it this way:  a 15 year old bottle from France’s Côtes du Rhône will only vaguely resemble the recently harvested Aussie Shiraz that you opened last summer to sip poolside with the burgers in your backyard.  The challenge however, is that most patrons do not recognize how significantly a bottle of wine can change with time. ‘It’s flawed’ demanded the couple, and without even tasting the contents, ‘Take it away!’

One of the more fascinating aspects of the great transformation which occurs inside a bottle of wine is the concept of sedimentation. Save for a minute amount of oxygen transfer, the bottle is essentially a sealed environment and while nothing has entered or left the bottle, the composition of the contents has changed; in some cases rather significantly. Colour and tannin precipitate out of the liquid solution in the form of a powder-like sediment that collects in the bottle and this formation is both natural and inevitable the longer the bottle sits. During the winemaking process however, should the bottle not be subjected to cold stabilization (which I will explain shortly) a crystal-like mineral deposit may form and settle at the bottom or in some cases, adhere itself to the cork. Though formally known as Tartrates, these crystals are also referred to as Wine Diamonds.

Normally, the crystals are dull or colourless while on other occasions they remain bright and vibrant. What you are actually looking at is mineralized tartaric acid (potassium bitartrate crystals). It's harmless and contrary to popular belief, does not indicate a flawed bottle of wine. Wine diamonds develop only under certain conditions and are an indication of well made wine. Generally, the grapes used in the production of a wine which develops tartrates were allow to full ripen on the vine and thus contain a higher brix level (sugar content). Additionally, the fermentation process was not accelerated nor artificially tampered with to expedite the bottling process - hence, well made wine.

In North America, we don't readily accept unfiltered wine as the normal; simply put, people don't want bits of stuff floating about in their wine glass. To prevent this, the wine is filtered several times and in some cases, subjected to a process called 'Cold Stabilization' - it just sounds bad doesn't it? It's actually very straightforward: To prevent the formation of tartaric acid minerals in the bottle, winemakers rapidly cool the wine in a large stainless steel tanks. The sudden cold temperature causes the tartaric acid to precipitate out of the liquid and fall to the bottle of the vessel. The clear wine is then pumped or siphoned off the top for bottling or additional filtering, but here is the catch, for clarity does not come without cost... Purists, enthusiasts, and those who claim to taste the difference in terrior from one row of vines to the next will attest that cold stabilization and excessive filtration also strips a wine of its unique personality and the more you drink wine that has not been over-processed, the sooner you will realize that they just might be correct.

The next time you pop a cork, remember that what goes on inside a sealed bottle of wine is still one of life’s great mysteries.  Don’t be too quick to find fault with the contents if something is seemingly out of place.  And if you do discover a few diamonds in the rough, consider yourself very fortunate.



  1. You have such interesting stories of 'wine sports'. Have you ever seen any full contact interactions?? I need to go to more exceiting restaurants.

  2. This is a good one to try though they do get very mixed reviews, but I think they also get a fair amount of snobbery which is rather unfortunate. I can easily choose my own bottle of wine off their list but instead, I let them recommend a wine to pair with our food choices. They seem to appreciate the request.

  3. Nice article Tyler. Too many people with just enough info on wine to make them dangerous find themselves out of sorts when confronted with a red that has sediment in the bottle or crystals on the cork. I happily accept the glass and explain more or less (less actually) what you shared in this article.

  4. I would hope the LCBO knows the difference between crystals every wine drinker knows are harmless and other sediment that needs to be investigated. A recent customer complaint included 'insects' & 'glass' with the crystals. Hyperimagination of real? I wonder when/if we'll ever know.

    1. Bugs, shards of glass, and tartaric acid crystals - that sounds like a story in the making!



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Tyler is a member of the Wine Writers' Circle of Canada and the Guild of Sommeliers. He writes about and reviews wine both online and via a variety of circulating publications. In 2009 Tyler founded North of 9 Fine Wine, a free public wine education resource where he publishes his Thoughts, Theory, and Recommendations. For additional vinous related information and learning, follow on Twitter @TylerOnWine