Induction sealing is a process that can create a hermetically sealed container without any physical contact taking place, which typically involves liners that are composed of foil and other materials. The liner is placed over the top of a container and then heated through induction. As it heats, wax or another sealing substance is warmed up and attaches it solidly to the container. Since induction sealing is a process that does not require direct contact, a lid can be placed over the foil liner prior to the sealing process. This procedure is used to seal everything a wide range of products, including medications, food products, motor oil, and others.
In the late 1950s, the concept of induction sealing was developed to solve the problem of liquids leaking out of sealed containers. The first induction sealers used vacuum tube technology, though solid state devices were soon introduced. Large units are capable of automatically processing containers using conveyor belts, though induction sealing can also be carried out with small, handheld devices.
Many of the early uses of induction sealing were to keep liquids from spilling out of containers during transit. Later uses extended to keeping foodstuffs fresh for longer periods of time, due to the hermetically sealed nature of the containers. A variety of events led to the creation of tamper-resistant seals for medications. One of the preferred methods for creating these containers is induction sealing.
The materials used to create the foil liners can be designed to leave a visible residue on the container. If this residue is present when a consumer purchases medicine, it is readily apparent that the product has been tampered with. Other foil liners are designed to leave no residue, which is typically more desirable when packaging foodstuffs. If a large amount of residue was left behind, it could contaminate the food item or interfere with its use.
One of the primary benefits offered by induction sealing is that there is no contact required between the heating apparatus and the bottle. This can allow an induction sealer to work with a variety of container sizes and can also speed up the process. Since there is no physical contact required, the container can have the liner applied, a lid placed on, and then pass under an induction sealer all on the same conveyor assembly line. With processes such as conductive sealing, physical contact is required between a metal plate and the liner, which can slow down processing.