Reader Gustav asks if the tartaric acid (cream of tartar) crystals that form on wine corks happen all the time or only if the wine has “turned.” The answer is that tartaric acid crystals can form anytime in just about any wine (white or red) and do not indicate that a wine has “turned” in any way. In fact tartrate crystals on the inside end of a cork probably indicate that you’re in possession of a rather good bottle. Mass producers of wine, knowing that wine drinkers are frequently put off by tartrate crystals (making them prone to return opened bottles) chill — or “cold stabilize” — their wines, so that the tartrate crystals form in the vat and not later in the bottle. Purists insist that this extra processing step detracts from a wine’s character, and so smaller vintners tend to omit it. This is especially true where red wine is concerned. White wine producers tend to do more cold stabilization since white tartrate crystals are so frequently mistaken for tiny shards of glass.