Bottle caps, or Closures, are used to seal the openings of bottles of many types. They can be small circular pieces of metal with plastic backings, and for plastic bottles a plastic cap is used instead. A bottle cap is typically colorfully decorated with the logo of the brand of beverage. Caps can also be plastic, sometimes with a pour spout. Bottle caps are often made of a different type of plastic than the bottle itself, and are often recyclable.
Bottle caps were originally designed to be pressed over and around the top of a glass bottle to grab a small flange on the bottle neck. The Crown Cork was patented by William Painter on February 2, 1892 (U.S. Patent 468,258). It originally 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 required.
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 widely used in the United States and Australia. This bottle cap is pressed around screw threads instead of a flange. Such a bottle cap can be taken off merely by twisting the cap.
Bottle caps are also a way for bottlers to hold promotions, especially for soda companies. A message is printed on the inside of the cap and people with the right message may win a prize. Since the bottle must be purchased to determine the message and win, people usually purchase more of the drink to increase their chances of winning. The most common prize is a free soda from that company.
Some companies, such as Snapple, also print interesting facts on the inside of their caps.Mickey's Malt Liquor as well, prints riddles underneath the 24 and 40 oz. bottle caps. Usually this is done on wide-mouthed bottles that have large caps with enough printing area to put a short sentence.