The Anatomy of a Barrel
Wine and whiskey barrels are usually made of oak, which has to be dried (either by air or in a kiln) to a low moisture content (usually 10-12 percent) before it can be shaped. The individual pieces that are split and/or sawn to form a barrel are called staves. These are assembled by the barrel-maker, or cooper, around metal rings called hoops, and then bent over a fire or by steam. More hoops are added to form the basic barrel shape. The barrel is then placed over a fire to “toast” the oak inside—from a light toast for some wine barrels to a heavy char for whiskey barrels. (Sometimes the heads are toasted as well.) This adds additional flavors to whatever liquid is put into the barrel. Then the heads of the barrel are forced into the groove, or croze, at each end of the barrel, and hoops are tightened. Traditional barrels are made without nails or glue; wooden pegs are used to hold the cants, or sections of the head, together. Otherwise, they remain tight only from the pressure of the liquid inside. Without sufficient swelling of the wood, barrels will come apart. Because wood can’t be sterilized like stainless steel tanks, aerobic bacteria can make barrels go sour if they are not kept full. While winemakers try to avoid this, it’s an advantage to brewers in making some Belgian-style ales.