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Bottle caps, or closures, are used to seal the
openings of bottles of many types. They can be small circular pieces
of metal, usually steel, 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. Flip-Top caps like
Flapper closures provide controlled dispensing of dry products.
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 bottleneck.
The Crown Cork was patented by William Painter on 2 February 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 generally advised, although some bottles
incorporate a screw cap, eliminating the need for the opener.
Individuals have experimented with different ways of opening
bottles, including using teeth or snapping them open across another
surface. A separate interest to collecting bottle caps is that of
interesting ways to open bottles.
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, Canada, 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.
Purpose of closures
Many containers and packages require a means of closing. It can be a
separate device or seal or sometimes a integral latch or lock.
Depending on the contents and container, closures have several
functions:
Keep the container closed and the contents contained for the
specified shelf life until time of opening
Provide a barrier to dirt, oxygen, moisture, etc. Control of
permeation is critical to many types of products: foods, chemicals,
etc.
Keep the product secure from undesired premature opening
Provide a means of reclosing or reusing the container
Assist in dispensing and use of product
Allow reasonable ease to open the container by the intended user.
Difficult to open containers may cause wrap rage. The force or
torque required to open a closure is an important consideration for
packaging engineers.
Many types of packaging with their closures are regulated for
strength, safety, security, communication, recycling, and
environmental requirements.
Types of closures
Closures need a means of attaching to the container with sufficient
security. Threads, lugs, hinges, locks, adhesives, etc. are used.
Many closures need to have the ability to adjust to slight
manufacturing variation in the container and the closure structure.
Some closures are made of flexible material such as cork, rubber, or
plastic foam. Often an o-ring or a closure liner (gasket made of
pulp or foam cap liner) is used. Linerless closures often use a
deformable plastic rim or structure to maintain the seal.
Secondary seals are common with sensitive products that may
deteriorate or where extra security is needed. Foil or plastic
innerseals are used on some bottles, Heat sealed lidding films are
used on some tubs. External shrink bands, labels, and tapes are
sometimes used outside the primary closure structure.
Screw top
A screw closure is a mechanical device which is screwed on and off
of a threaded "finish" on a container. Either continuous threads
(C-T) or lugs are used. Metal caps can be either preformed or in
some instances, rolled on after application. Plastic caps may use
several types of molded polymer.
Some screw tops have multiple pieces. For example, a mason jar often
has a lid with a built in rubbery seal and a separate threaded ring
or band.
Crown caps
Beverage bottles are frequently closed with crown beverage caps.
These are shallow metal caps that are crimped into locking position
around the head of the bottle.
Snap on
Some closures snap on . For opening , the top is designed to pry off
or , break off, or have a built in dispenser.
Friction fit
Some containers have a loose lid for a closure. Laboratory glassware
often has ground glass joints that allow the pieces to be fitted
together easily.
An Interference fit or friction fit requires some force to close and
open, providing additional security. Paint cans often have a
friction fit plug.
Dispensing
A wide variety of convenience dispensing features can be built in to
closures. Spray bottles and cans with aerosol spray have special
closure requirements. Pour spouts, measuring attachments, sifting
devices, etc. are common.
History
Early pottery and ceramic containers often had lids that fit
reasonably snug onto the body of the container. The narrow necks of
ancient amphora were closed with a plug of cork, wood, or ceramic
and sealed with mortar.[3] Wooden Barrels often had bungholes closed
by cork or wood bungs.
Some early tinplate cans were made with threaded necks for screw top
closures.
Beverage bottles started using the Hutter Stopper in 1893. This
involved a porcelain plug fitted with a rubber washer, which was
then forced down into the lip of the bottle. This technique only
works with carbonated beverages. The Hutter Stopper became standard
in beer bottling in the late 1890s / early 1900s. Bail closures on
bottles were invented by Henry William Putnam in 1859. These
involved heavy wire bail attached to a bottle's neck that swung over
the cork to hold it in.
The world's first modern bottle cap, the crown cork, was invented by
William Painter in 1890 in Baltimore. The screw cap using rust
resistant aluminum was first used in prescription drug bottling in
the 1920s.Molded urea based bottle caps were first introduced in the
early 1900s.
A history of accidents involving children opening household
packaging and ingesting the contents led the US Congress to pass the
Poison Prevention Packaging Act of 1970.