Let’s say you went to someone’s house for dinner and presented a young, big red wine—say, a Michele Chiarlo Barolo Cerequio 2003 ($90)—as a gift. The host looks it over and promptly pours it into a decanter, leaving it there for an hour before serving. Clearly the host is:

a)    a pretentious poseur and snob

b)    a worrywart

c)    uninformed

d)    from Paris

e)    quite savvy about the ways of wine

Well, I don’t know your friend. He might be a snobby Parisian worrywart, but he’s definitely e), too. Decanting is perhaps the cheapest and easiest way to be a wine sophisticate in a world where the bottles themselves are getting more expensive all the time.

Decanting should be done in two cases: When you’re dealing with an older red and you suspect there’s some sediment in the bottle that you’d rather not have in your glass, and when you have a young, tannic red that needs to breathe.

Let’s take these scenarios one by one. Decanting is, predictably, great for getting rid of the weird chunky stuff wine can produce: tannins and pigments that simply separate over time and settle at the bottom of the bottle. It’s no big deal, but you also don’t want to be drinking that stuff. (Trust me on this; I’ve done it. It’s like unexpectedly swallowing a cardboard flan.) This probably isn’t an issue for reds less than a decade old, but it varies with wine types, so if you want to check, just hold your bottle up to a light (a candle or flashlight underneath usually does the trick, but sometimes it’s hard to tell with dark bottle colors).

What a lot of folks don’t know is that sediment is only part of the picture. Decanting feisty, under-five-year-old reds like those from the Northern Rhone region of France is a great idea because these wines tend to be ungenerous at that age—meaning the flavors haven’t had a chance to open up yet. In truth, oxygen helps release the aroma and taste of most red wines, regardless of age. (We keep it in a bottle in the first place so that this doesn’t happen until we’re ready.) Letting your red hang out in a decanter for 30 or 60 minutes will make it more expressive. It “breathes,” or becomes less tight and simply provides more of what it’s got.

I wish I had decanted a bottle of Ladera Vineyards Cabernet Sauvignon Howell Mountain 2004 ($85) the other day. I served it hastily, and though I could tell it was plush, balanced, and full of fruit, I could also tell that it wasn’t giving me the full picture just yet. After a half-hour in the glass, the black cherry notes, for instance, became sweeter, fuller, and rounder.

As a bonus, “opening up” a wine also gives you a sense of how it will age. Decanting a bottle is like fast-forwarding its development, since oxidation essentially equals aging. Serena Sutcliffe, the worldwide head of Sotheby’s wine department, told me she loves to leave a little bit of red in her glass overnight. When she wakes up, she gives it a taste, getting a quick picture of what the wine will be like many years down the road.

So is decanting ever a bad idea? Rarely. If you have very old, very delicate wines, decanting them for too long can dry them out and hasten them to an early grave. It’s depressing when this happens, but it’s a pretty unusual scenario indeed for most wine drinkers—if you are drinking a lot of grand cru Burgundies from the 1960s, for instance, you don’t need to be reading this column anyway.

With reds, my rule is to decant it and see what happens. It generally can’t hurt, and it will probably help. In two weeks, in the second part of this column on decanting, I’ll talk about how to do it properly, and in what.

Ted Loos, executive editor of Art+Auction magazine, is the former features editor of Wine Spectator and has written on wine for Bon Appétit, Town & Country, and many other publications. He's the author of Town & Country Wine Companion: A Tasting Guide and Journal (Hearst Books; $12.95), published in fall 2007. "In the Cellar" appears on ARTINFO every other Wednesday.