Paul, I recently had a red wine selection from your club that showed little crystals on the bottom of the cork. What are they and are they harmful ?
As wine ages in the bottle the saturation level of the natural ingredients changes. Very often in both red and white wines tartaric crystals will form on the cork and or otherwise settle on the bottom of the bottle. As a result of changes in temperature these crystals are formed and are often mistaken for a flaw in the wine or even shredded glass. The reality of these little gems is that they are harmless and in fact, prove that a wine is totally natural and untampered. There are ways to minimize or even eliminate this physical reaction. But this requires introduction of chemicals to the wine, and many winemakers opt not to do this.
As a purist, I find it much more acceptable to decant or filter out the crystals and enjoy the wine in its natural state rather than introduce chemicals that may upset the natural balance and/or shorten the ageing life of the wine.
Next time when you look at the cork and see nicely formed crystals, don’t be alarmed. Even if these are ingested they are harmless. Go ahead and decant or just pour carefully and enjoy a nice pure bottle of wine.