Most food and
beverage cans are produced separately from the rest of the body of
the can. The can ends or lids are attached to the filled cans
towards the end of the process. So, the fillers purchase the can
ends and the seams for the lids separately. The can ends
are seamed to the body of the cans to provide a hermetic seal. The
exception to this rule are the cookies tins which have a
double seam and other techniques to seal as they have a different
function.
The classic can
ends are normally used for food rather than for beverages which
are circular in shape and have circular ridges. These ridges can also
have expansion rings that allow for any change in the volume of the
food during the heating process. However, the easy-open can ends
are the most popular ones as they are designed to be easily opened by
the customer without the use of any can openers. They are also safer
for the supplier to attach with fewer lacerations caused due to
jagged edges.
Closures is the
technical term for lids used for pickles, ketchups and cookies tins. They are reusable and resealable lids and can be made of
metal or plastic. The inside of these closures is generally coated
and provide sufficient flexibility and deformability to provide an
airtight seal. They can be further classified into two large groups,
roll-on and pre-threaded. The roll-on closures provide the closing
when they come in contact with the smooth surface of the bottle.
However, most
cookies tins and some of the tea products traditionally come
in tin boxes. Their shape could be cylindrical or rectangular and the
lids are not seamed but are formed as a slip on or to plug the top.
Such lids usually have an additional layer of plastic or foam
material to protect the contents from spoilage due to environmental
conditions. This plastic is usually the only material that comes in
contact with the lid until opened. The food items in such boxes
cannot be processed like the rest of the food and beverages and serve
only as stylistic options.
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