The main reason for decanting red wines is to separate the wine from the sediment that may have formed in the bottle over the years. This sediment consists mainly of the tannins that have been made insoluble by the chemical reactions responsible for the ageing process. The decanting operation is accompanied by some oxygenation, which is often beneficial to young and powerful wines but which could, in fact, be damaging to the oldest wines. For young wines, it isn’t necessary to decant because there is generally no sediment in the bottle. But a light aeration often helps them to “open up”, that is to say to show their aromas better. One can choose either to decant them or to leave them in the glass a moment before drinking them.
As soon as the wines have sediment in the bottle, it’s better to decant them whatever their age. The simplest way is to carefully decant the wine into a carafe – or another bottle – above a lighted candle. The sediment will slide along the bottle into the shoulder and the neck of the bottle. In general, it’s better not to decant too long before serving.
It’s not necessary to decant the Pavillon Blanc du Château Margaux when it’s young. But after a few years, it’s preferable to pour it into a carafe before serving.