Barrel - Shape

Shape

Barrels often have a convex shape, bulging at the middle. This constant bulge makes it easier to roll a well-built wooden barrel on its side, changing directions with little friction. It also helps to distribute stress evenly in the material by making the container more spherical.

Casks used for ale or beer have shives and keystones in their openings. Before serving the beer a spile is hammered into the shive and a tap into the keystone.

The rings holding a wooden barrel together are called "hoops" and are generally made of galvanized iron, though historically were made from flexible bits of wood called withies. While wooden hoops could require barrels to be "fully hooped", with hoops stacked tightly together along the entire top and bottom third of a barrel, iron-hooped barrels only require a few hoops on each end. The "head hoop" or "chime hoop" is the hoop nearest the extremes of a barrel, the chime being the beveled edge and the head being the flat circular top or bottom of the barrel. The "bilge hoops" are those nearest the bilge, or bulging center, while the "quarter hoop" is located between the two. The stopper used to seal the (bung)hole in a barrel is called the bung and mostly made of silicone.