However, the effectiveness of decanting is a topic of debate, with some wine experts such as oenologist Émile Peynaud claiming that the prolonged exposure to oxygen actually diffuses and dissipates more aroma compounds than it stimulates, in contrast to the effects of the smaller scale exposure and immediate release that swirling the wine in a drinker's glass has.  In addition it has been reported that the process of decanting over a period of a few hours does not have the effect of softening tannins. The softening of tannins occurs during the winemaking and oak aging when tannins go through a process of polymerization that can last days or weeks; decanting merely alters the perception of sulfites and other chemical compounds in the wine through oxidation, which can give some drinkers the sense of softer tannins in the wine.  In line with the view that decanting can dissipate aromas, wine expert Kerin O'Keefe prefers to let the wine evolve slowly and naturally in the bottle, by uncorking it a few hours ahead, a practice suggested by wine producers such as Bartolo Mascarello and Franco Biondi Santi . 
What’s the purpose, then? Aesthetics. Though decanters did begin practically—historically it was how you got your whiskey from the barrel—these days they’re almost entirely about looks, which can range from the broad-shouldered, wide-bottomed classic to something you’d definitely see on the giant mahogany desk of a Bond villain . As long as you’re not planning on keeping that whiskey for a long time (in which case, you’d simply leave it in the bottle), decant or don’t, it’s up to you. Just make sure it isn’t a lead crystal decanter. Yes, they’re sparklier, but the cost of that sparkle could be lead leaching into your whiskey (it’ll take a while, but it happens), and that, most definitely, will change things.