5 Myths of Induction Cap Sealing

Myth 1: Only some of my containers sealed correctly. There’s a problem with my induction sealer.

Induction sealers are designed to emit a consistent energy field at a given power. If one or more containers seal successfully through this energy field then identical containers under the same conditions should also seal. When packers find that not all of their containes are sealing properly the first place to look are the containers and materials themselves.

The most common reason is related to insufficient or inconsistent cap torque. You can learn more about cap torque here. You should also check to make sure that caps are not cocked or mis-threaded and that the bottle seating areas do not have uneven surfaces or burrs.

If you are working with high volumes of containers, whether it’s hundreds or millions of units, it’s normal to encounter occasional defects.

We’ve created an easy-to-follow infographic ‘Troubleshooting Induction Sealing’ to help you quickly identify and resolve common sealing issues.

Myth 2: An induction seal is too difficult for the consumer to remove. 

While an induction seal needs to be secure and strong enough to withstand mechanical, environmental and chemical pressures, it doesn’t need to be hard to remove.

The peel strength of an induction seal can be customised to suit the application and the desired consumer experience.

If a seal is excessively difficult to remove, it is often the result of over-heating during the induction sealing process. Excess heat can cause the polymer layer of the liner to bond too deeply to the container rim, creating a stronger-than-intended seal. This can occur if the machine power is set too high, the line speed is too slow, or the liner material is not well matched to the container.

In some applications, manufacturers may intentionally create a stronger seal to provide maximum product protection, leak prevention, and tamper evidence. However, when consumer convenience is important, liner manufacturers offer solutions designed for easy opening.

Many induction liners are available with convenient clean-peel tabs, allowing consumers to quickly and easily remove the seal. These liners are commonly used on products such as liquids and sauces, where both product protection and accessibility are important.

By choosing a compatible liner and optimising your sealing process, packagers can achieve the ideal balance between product protection and consumer convenience.

Myth 3: The overhang on my foil seal doesn’t matter. 

Foil overhang can cause sealing issues.

The overhang can result in the liner bonding not only to the container rim, but also to the cap. This makes it difficult to remove and can cause the liner to peel away when the cap is removed.

Over hanging foil can also increase the risk of seal failure. If the liner edge is too far past the closure edge, the energy can become concentrated at the edge rather than where the closure and liner meet. This can result in a weak seal or failed seal.

Myth 4: Induction sealing only works on plastic bottles

While induction sealing is commonly used on plastic containers, in certain circumstances it can also be successfully applied to glass and metal packaging, plus tin plate and aluminum plate caps.

These applications have additional considerations and one of the keys to achieving a reliable seal is ensuring the container neck finish and foil liner are compatible.

For example, most glass containers are treated during the manufacturing process, so it’s essential that the polymer coating on the foil liner is suitable for the treatment applied to the glass. Using the wrong combination can affect seal performance and integrity. Additionally, dry products make better candidates for sealing in glass than liquids.

Metal packaging and caps can often be induction sealed, but care must be taken as power requirements can be higher and caution must be used in handling the metal packaging materials immediately after sealing due to heat.

Your foil supplier should be able to advise on the most suitable liner specification. However, if you’re unsure, our experts are here to help. We also offer free application testing, allowing you to assess product compatibility and sealing performance before investing in a machine.

Myth 5: A higher wattage induction sealer delivers better performance 

A higher kW rating does not automatically translate into better induction sealing performance.

While a higher-powered system can generate more energy, sealing efficiency depends on how effectively that energy is transferred from the power supply to the foil seal. Simply increasing power output does not guarantee higher sealing speeds or improved seal quality.

One of the most important factors in sealing efficiency is the sealing head design, also known as the sealing coil. The size, shape, and configuration of the sealing head determines how effectively inductive energy is transferred into the foil liner.

This is where our induction sealing technology stands apart.

Our engineering team has developed the widest range of sealing coils designed to maximise energy transfer during the sealing process. By focusing energy precisely where it is needed, our systems minimise wasted energy and deliver more efficient sealing performance. As a result, our equipment can often achieve the same or better sealing results while consuming significantly less power, resulting in lower operating costs for our customers.