[1]The decanter may seem like a vessel of a bygone era. Today one doesn’t find many people serving their wines out of a decanter but connoisseurs still know the importance of it. A decanter is a vessel that is used to hold the decantation of a liquid (such as wine), which may contain sediment.
Another reason for decanting wine is to aerate it, or allow it to “breathe”. The decanter is meant to mimic the effects of swirling the wine glass to stimulate the oxidation processes, which trigger the release of more aroma compounds.
Liquid from another vessel is poured into the decanter in order to separate a small volume of liquid, containing the sediment, from a larger volume of “clear” liquid, which is free of such. In the process, the sediment is left in the original vessel, and the clear liquid is transferred to the decanter.
Decanters have been used for serving wines that are laden with sediments in the original bottle. These sediments could be the result of a very old wine or one that was not filtered or clarified during the winemaking process.
In most modern winemaking, the need to decant for this purpose has been significantly reduced, because many wines no longer produce a significant amount of sediment as they age.
Links:
[1] http://archive.asianage.com/decanterjpg-541