What Are Bottle Caps Made Of?

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Soda bottle caps

Bottle caps have been around since the 1800s. The first patent was established in 1892 by William Painter. The early caps required the use of a bottle opener. Bottle caps are used to keep beverages from spoiling. They are used on various types of bottles and are made out of different materials.


Materials in Bottle Caps

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Metal bottle caps

The most common type of bottle cap is the plastic cap. Plastic bottle caps are made of polyethylene terephthalate. It is a thermoplastic polymer resin that is a part of the polyester family. This kind of plastic is widely used in beverage and food containers. Depending on the processing method, this material can appear transparent, opaque or white. This type of plastic is usually has the PET abbreviation. It is a different plastic than what the bottle itself is made of. Metal bottle caps are made of steel.

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How Bottle Caps are Made

The plastic caps are created by injection molding. The plastic ingredients are put into a machine that heats and mixes them, then pushed into a mold cavity. In the mold cavity it will cool off and harden to that mold shape. Metal bottle caps are shaped with a machine that creates the dips along the edges. Some metal caps have an additional plastic coating put over them.



Most bottle caps have company logos printed on them. Plastic bottle caps are used on plastic-type bottles and metal caps on glass bottles. Threads are usually grooved inside the caps for easy twist-off caps. Older style metal bottle caps require a bottle opener to remove. Some caps have a flip-top opening. Often companies print code or game information inside the caps for contests. Some companies such as Snapple, print educational information inside their caps.


Uses For Bottle Caps

Bottle caps are used to seal in freshness of beverages or liquids. They also can be recycled, which is good for the environment. Bottle caps are even considered currency in certain video games such as Fallout. They can be used in craft projects. You can create pictures arranging different colored metal bottle caps on a cork board. Or you can glue several metal caps together into a shape of your choice to make trivets. They are even collectible items.



The first bottle caps were created in February of 1892 by William Painter. They consisted of the metal caps with 24 teeth and a cork with paper backing separating the metal cap from the liquid contents in the bottle. They required the use of a bottle opener to pop them open. Metal caps now have only 21 teeth and do not have the cork separating them. Twist-off bottle caps were introduced in the 1960s in Germany. They are sealed on the bottle with threads instead of over a flange. These caps do not require use of a bottle opener. They are widely used in the United States, Australia, Canada and other countries.



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