As with any compound, wines are altered by the introduction of oxygen. With younger wines, oxygen speeds up the wine's softening. Tannic red wines are often decanted to soften the coarse taste of tannins and to let their aromas develop. Tannic wines may be decanted and left to sit in a vessel which permits greater surface exposure to oxygen. Red wines may develop lees from ages eight to twelve years.
Lees are a naturally occurring material from grape solids and tartrates suspended in the wine.
Traditionally, lees have been associated with the longest lived and heaviest styled red wines. The bottle styles of Bordeaux, for example, have an extreme sloped shoulder as opposed to the gently sloping shoulder of a Burgundian bottle. Their shoulder is meant to act as a basin to catch this sediment prior to exiting into a glass. The punt or the indentation of the bottle also aids the prevention of sediment movement to the neck of the bottle. Wine may be traditionally decanted or industrially decanted.