There are, in the wine world, a few obnoxious practices that suddenly gain an undeserved and unfortunate popularity: drinking chilled white wines, oak-aging abuse, over-extraction leading to hyper-alcoholic wines are just a few examples. Among them, there is one that is now almost universally accepted and that I find particularly disturbing: decanting red wines. Decanting wines is not bad per se but, as usual, a good practice turned into a bad one for the wrong reasons: and now, everybody indiscriminately decants red wines, regardless whether it is necessary or not. What's more, decanting a wine can destroy its delicate equilibrium, reached after years of quiet and undisturbed rest in the bottle.
The practice of decanting was necessary, several years ago, as most old wines (and even younger ones) presented such a severe deposit that drinking them was totally unpleasant. A savvy drinker had to leave the bottle upright for a few days then carefully and slowly pour the wine from the bottle to a decanter avoiding the deposit to fall into it (a candle illuminating the bottle could help seeing the deposit more clearly). It was a painful operation that required patience and skills; moreover, quite a few sips of the wine had to be thrown away (if you are a fan of Lieutenant Columbo, you might remember an episode where decanting a wine was part of our hero's uncovering of the villain's criminal plan). Today, deposits in wines are much less frequent as filtration and stabilization are common practices in modern winemaking.
Today decanting is used mainly to oxygenate the wine, helping the flavors to emerge clearly and eliminating reduction smells (often described as rotting vegetation, a just-struck match, hardboiled eggs, sewage, and burnt rubber). It's true that oxygenation is required to smell the wine bouquet and that reductive smells can frequently be get rid of with proper airing but we must not forget that oxygen is also a highly corrosive gas and that in medio stat virtus. (Virtue stands in the middle.) Too much oxygen can ruin a wonderful wine, forever! Just think about it: you have a great wine, calmly resting in your dark cellar for 20 or 30 years and, suddenly, you uncork it, pour it into a large decanter and start shaking it like in a roller coaster. Think of what happens to ancient books and paintings when they are dug from underground tombs, rooms and caves and exposed to fresh air once again after centuries. Even if the wine is strong enough to withstand the decanter, you are missing the wonderful evolution of flavors you could witness leaving the wine in the proper glass for a while, sipping it every few minutes. (A balloon glass is the right tool to properly oxygenate the wine.) Using a decanter to help the wine evolve quickly is like skipping to the last page of a crime story.
So, is decanting always bad? No, there are indeed situations in which decanting is highly recommended: decanting young wines (especially white wines) helps getting rid of sulfites (the main cause of hangovers) and other youth flaws (like unwanted fizziness or foul odors from unclean barrels). Of course, if there are deposits in the wine, decanting is imperative but must be conducted properly: I also recommend using a tall and thin decanter or a pitcher instead of the trendy short and fat decanters everybody uses.
Next time you taste an old gem, try not decanting it: slowly savor it from the glass. If you don't like it, you can still decant the wine eventually. The vice versa is not possible!