a container made from wooden staves. The construction may be “slack” or “tight.” Slack barrels have been made since Roman times for dry goods—hence, for instance, cracker barrels—whereas tight barrels for wet goods such as beer and wine, as well as for oil, olives, fat, vinegar, sauerkraut, and pickles, came into use only in the early Middle Ages. Barrels often come by different names depending on their size and function. There are firkins and hogsheads for beer and pipes for Port and Madeira wines. Most barrels are made from staves of hardwood, often oak, bound together by metal hoops into a bulging cylinder. The bulge, which makes it easy to roll and spin the barrel, is called a bilge. The barrel’s head and bottom are flat and each is secured into the staves by a grove called a croze. This allows the staves to protrude above the head and bottom in a ring called a chime, which makes it easy to grip and roll the barrel.

Photograph, c. 1935, of a Pinkus Müller brewhouse-style restaurant in Münster, Germany. The decorative barrel portrays Jan Gambrinus, the mythical Flemish king of beer. courtesy of pinkus müller

The quality of the barrel depends largely on the expert selection of the wood. Straight-growing trees are preferred. The staves are split from the felled trees and planed. Then they are piled up in tiers in the open, where they age and season for several years, while air and water reduce the wood’s green, unpleasant, tannic flavors. During the barrel’s construction, the cooper moistens the staves and then lights a small wood fire inside the emerging barrel to heat the wood and make it more pliable for bending into the typical barrel shape. The fire chars or “toasts” the inside of the barrel. Toasting levels range from light to medium to heavy, which, in turn have an impact on the flavors of their contents, be it wine or whiskey. Used toasted or charred barrels are highly sought after by specialty brewers for barrel aging. See barrel-aging.

However, barrels that are intended as simple containers rather than aging vessels do not take a prior detour through a winery or distillery. Instead, they are often coated on the inside to keep the beer from making contact with the wood. In years past, the material of choice for lining barrels was pitch, a type of tar. Nowadays, the protective blanket between the beer and the barrel tends to be made from various modern, inert, elastic, sturdy, rubber-like materials.

Wooden beer barrels are still used—commonly for gravity dispensing—by several traditional breweries, such as the Altbier Brewpub Zum Uerige in Düsseldorf and the Rauchbier Brewery Schlenkerla in Bamberg, both in Germany. See altbier, gravity dispense, rauchbier, and uerige brewery. A few British breweries still use wooden casks. As of 2011, the Wadworth Brewery of Wiltshire employed England’s last fully trained master cooper for the upkeep of the brewery’s wooden casks. Theakstons and Samuel Smith’s still do limited trade in wooden casks, and Marston’s Pedigree has the distinction of actually being fermented in barrels through the Burton Union sets. See burton union system, marston’s brewery, samuel smith’s old brewery, and theakstons. In 1963, British barrel enthusiasts founded the Society for the Preservation of Beers from the Wood, their aims being exactly as described.

Barrels are typically fitted with several openings for filling, cleaning, and emptying, as well as for air to enter the barrel as the liquid is drained. The opening for cleaning, sanitizing, and filling is called a belly bung. The opening for emptying the barrel via a tap or a beer engine is called a keystone, kept shut with a stopper. See beer engine, cask. During tapping, the keystone stopper gets pushed into the beer. For venting, a classic British cask has a shive with a center hole for a stopper called a tut and a hard wooden peg called a spile, the latter being hammered into the tut. The spile can be removed and reinserted during poring to vent the cask.