A bung, made of glass, plastic, rubber, earthenware, silicone, or wood, is a barrel’s stopper, analogous to the cork of a bottle. It is inserted in a bung-hole. If a barrel is stored so that the bung is at its highest point, this position is called bung up and the bung may be left so that gas can escape from the bung-hole. Some bungs even incorporate a device that encourages this. If a barrel is stored with the bung at either two or ten o’clock, the position is called bung over.
Since oxygen tends to enter a barrel around the bung-hole, silicone bungs are sometimes used to keep a particularly tight fit. These silicone bungs also have the advantage of being gentler on the bung stave, the stave in which the bung-hole is drilled, which is weakened and sometimes cracked by the constant hammering needed on wooden bungs.
