A plastic bottle cap on a water bottleBeer bottle, with a Crown cork
Bottle caps are used to seal the opening of bottles. For glass bottles, these are usually small, specially adapted pieces of metal. With plastic bottles, plastic caps are used instead.
The original bottle cap was called Crown cork. It is pressed onto the bottle, and can be removed, using a bottle opener.
In recent years bottle caps with screw on mounts are used that way, a bottle opener is no longer required. Caps for plastic bottles are often made of a different type of plastic from the bottle.
A cork is another type of closure for the top of a bottle.
Bottle caps were invented in 1892 when young scientist Colt Williams wanted the water in his bottle to not spill.
