The right cap

Depending on the application, there are different requirements for caps. Its first function is to act as a seal for the bottle. However, if the bottle is under pressure, the pressure must be reduced to prevent the cap being "shot" from the neck when opening the bottle. To achieve this, part of the thread and the cap must have vent slots. A two-part cap with sealing ring is to be used for bottles that are under pressure or have a vacuum. An inner seal with a single-part cap is sufficient for pressure-free bottles.

For aseptic filling cap sterlization result in additional costs. This can be avoided if the opening is sealed with an aluminium disc during the aseptic process to meet the aseptic requirement for a simple cap. The choice of opening size is determined by the viscosity of the content and application by the end consumer. High expenditure for the bottle barrier is only reasonable if the cap is also equipped with a properly functioning barrier. If the latter is not provided this results in more than 50% permeation losses.