Decanting is the process of pouring out a bottle of wine into another container, known as a decanter, while holding it over a light source. The light source allows you to see the sediment coming up and therefore immediately stop the process. Although decanting a bottle of wine is not an absolute necessity, older red wines and very young wines should be decanted for quality purposes. In older wines, sediments tend to accumulate and disrupt the clarity of the wine. Younger wines are especially tannin and decanting them several times helps mix them with the air them and soften the overall flavor. Older bottles of wine should be set upright for several hours or days before opening and decanting ensue. This helps the sediment collect at the bottom of the bottle and makes it easier to decant.
Decanting a smaller amount into a wine glass is a good idea when drinking alone. Leaving a glass of wine sitting out for couple hours will help it oxidize and release its full aromas. Older wines should be enjoyed immediately after decanting whereas younger wines need to be set aside in the decanter for a few hours. Young wines also don't have to be decanted as carefully as older wines. Decanters come in many shapes, sizes and designs. A couple of things to keep in mind when purchasing a decanter include the clarity and heft of the glass.