Bottle cap

A bottle cap seals the top opening of a bottle. A cap is typically colorfully decorated with the logo of the brand of beverage, but not always. 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. To open these bottles, a bottle opener is generally used.

The height of the crown cap was reduced and specified in the German standard DIN 6099 in the 1960s. This also defined the "twist-off" crown cap, now used in the United States, Canada, and Australia. This cap is pressed around screw threads instead of a flange, and can be removed by twisting the cap by hand, eliminating the need for an opener.

The "flip-top" or "swing-top" consists of a plastic or ceramic stopper held in place by a set of wires. Prior to the invention of the crown cork, this was the dominant method of sealing bottles that contained carbonated liquid.

An opened "flip-top" bottle

A pair of bottles with flip-top closures

Plastic bottle screw cap used to seal a plastic bottle.

Glass stoppers for wine bottles and a cork stopper.

A "sports cap" made of plastic, as seen on many water bottles, here seen in closed configuration.

Same sports cap in open mode, allowing the liquid to pass around the central blue piece.

A recloseable wire, ceramic, and rubber bottle clasp, from a German mineral water bottle.

Bottle closer.

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Wikipedia