A bottle cap seals the top opening of a bottle. A cap is typically colorfully decorated with the logo of the brand of beverage. Plastic caps are used for plastic bottles, while metal with plastic backing is used for glass; the metal is usually steel.
Plastic caps may have a pour spout. Flip-Top caps like Flapper closures provide controlled dispensing of dry products. Caps for plastic bottles are often made of a different type of plastic than the bottle. Caps were originally designed to be pressed over and around the top of a glass bottle to grab a small flange on the bottleneck.
The crown cork was patented by William Painter on February 2, 1892 (U.S. Patent 468,258). It had 24 teeth and a cork seal with a paper backing to prevent contact between the contents and the metal cap. The current version has 21 teeth.