CAP

The cap is made up of a metal capsule (usually aluminium) which, using a manual or pneumatic capping machine, clings to the mouth (rims) of the bottle and a thin plastic gasket (in the first it was made of cork), located under the metal part internal, allows for watertightness. In addition to acting as a simple closure, the crown cap is used as an additional block of the underlying cork stopper, for highly gaseous wines.