There are two good reasons to decant a wine, they are; for older wines to separate the clear wine from any sediment or “crust” that has formed in the bottle as the wine has aged. For older and young wines it is to stimulate or enliven the wine by exposing it to air and giving it a chance to “breathe”.
“Double-decanting” is an excellent solution for big closed wines as it gives the wine a double dose of air. Older bottles should be stood up for a few hours (even a couple of days, if possible) and carried carefully from the cellar to the table so that any sediment is not disturbed. Open the bottle and pour the wine into a decanter (or jug) in a single, continuous stream with a minimum of “glugging” (to avoid stirring up the sediment).
If you like, you can use a candle or light underneath the bottle to see when the sediment enters the shoulder, but it is easier, if you have a marked jug, simply to stop pouring when the wine reaches the 720ml mark. Discard the last 30ml and rinse any remaining sediment out of the empty bottle with warm water. Now pour the decanted wine back into the bottle (a funnel is helpful).
It is clear that younger wines benefit most from decanting and breathing, which “opens them up”. There are no rules here – just a lot of trial and error. Generally, 2-4 hours decanting for a young wine is ideal however, some claim up to 8 hours is ideal for many younger wines. For older wines, time to decanter is a more volatile decision. It is wise to taste the wine say every 30 minutes and if it is deemed to be at its peak and still a while before a wine will be served, the bottle should be loosely re-corked or the decanter seal placed at the top. This is recommended for very old wines, which, may deteriorate quickly once exposed to air. Moreover, if you have a beautiful crystal decanter, pour the wine into it, rather than back into the bottle.
The origins of decanting emanated from the days when wines were made with a considerable amount of sediment and the primary purpose was to avoid this heavy deposit being poured into the glass. However not all wines will benefit from decanting and remember that wine and too much air do not make a very good mix. The argument for decanting to improve the flavor of a wine is based on the theory that small amounts of air already present in the bottle react with the wine to make it develop into something more complex therefore by decanting a wine would aerate it, thereby accelerating the aging process of the wine and improving the bouquet. On the other hand some experts argue that the effects of too much aeration can be harmful by exposing a delicate bouquet to air and that the interesting reactions between oxygen and wine are too complicated to be sped up. All that can happen is that the wine starts to oxidize too fast and therefore deteriorates.
We suggest that you decant young, big and closed wines some time before drinking them. For old wines where sediment is evident decant them just before serving. If once the wine has been poured, it is obvious that it is a bit tight and would benefit from more aeration, simply swirl it around in the glass, which is even more effective than the decanting process.