Decanting can be useful for a couple of reasons. Firstly it allows older red wines to be separated from any sediment that may have developed in bottle. I find the easiest way to do this is by standing the bottle up for a day or so before drinking- to allow sediment to settle to the bottom of the bottle; opening and then pouring the wine slowly and smoothly into a jug, or glass decanter. As soon as you see sediment coming out of the bottle stop pouring. Removing sediment, which can be quite bitter- being a combination of tartrate crystals and tannin- allows you to enjoy all the mature flavors of the wine without any unwelcome intrusions. Having decanted the wine, I’d advise giving the bottle a rinse with filtered water and pouring the wine back into the bottle and resealing it. This is because the process of decanting oxygenates the wine, which accelerates development. This process of decanting a wine and then putting it back into the bottle is called double decanting. Older red wines, decanted and left to stand for hours, quickly lose much of their delicate aroma, which simply volatilizes. This leaves us with not much to smell, and therefore little flavour. This is because our olfactory senses- which begin in our nose, are the greatest contributor to our sense of taste. Double decanting older reds, just moments before drinking, will give them a bit of a kick along without destroying them. Typically with younger wines I’ll double decant them a few hours prior to drinking (if I can wait that long) and when the time comes to drink them, they have typically opened up substantially. In spite of being resealed, the wine still opens up and softens, thanks to oxygen trapped in solution. I reckon this is the most gentle and effective means of bringing out the best in your wine.