barrel

A barrel is a hollow cylindrical container traditionally made of wooden staves bound by metal hoops, with flat ends called heads. In traditional cooperage, the interior may be toasted or charred to influence flavor and compatibility with the liquid it holds. Wooden barrels remain central to aging and maturation of beverages, though other materials are used for storage or shipping.

Barrels have long been used to store and transport wine, beer, spirits, oils, and other liquids. Aging in oak barrels can impart flavor compounds such as tannins, vanillin, and other aromas, while the porous wood allows slow exchange with the environment.

Capacities vary by commodity and region. In the oil industry, a barrel (bbl) equals 42 US gallons (about 159 liters). For beer, a typical US barrel is 31 US gallons (about 117 liters). A US wine barrel is commonly around 59 US gallons (about 225 liters); imperial sizes exist in other regions for different commodities.

Cooperage is the craft of making barrels. Oak is the preferred material in many traditions; American white oak and European oaks are common sources. The choice of oak and the level of toasting affect flavor, aroma, and tannin content. Modern practice also uses non-wood containers when aging is not required.

In addition to its container meaning, barrel also denotes a unit of volume used in trade and is used colloquially as a verb meaning to move quickly.