How to achieve perfect seals for bottles every time

seals for bottles

Products that are perfectly sealed on a seals for bottles machine provide consumer confidence in their quality and safety.

Manufacturers know that a poor quality seal on their products not only threatens consumer perception of their company and products, but also results in product loss and damage in transit.

Understanding how to identify and control induction sealing variables helps to achieve a perfect seal.

The process of developing a perfect sealing solution includes having the compatibility conditions between the lid, liner and sealer; setting an operating window; and establishing the testing method to identify a good seal.

Material Compatibility

A perfect seal can be achieved with any type of container.

The choice of the appropriate induction seal depends on the product to be packaged. If the product contains any volatile or potentially aggressive ingredients, chemicals, acids, solvents, high sodium content, alcohol or vinegar, a seal with a protective layer or barrier may be necessary and can be placed between the film being heated to seal and the foil to prevent corrosion.

Liners are the next consideration. One type of liners is a one-piece liners, which has a backing usually of cardboard, foam or a layer of paper. When induction is performed the entire structure is sealed to the mouth of the container with nothing left in the lid.

This type of liners is typically used for food, beverages and vitamins or for products that do not require another seal on the lid to seal the product once the foil has been removed.

Another classification is the two-piece liner. This is a two-piece wax-bonded material, which has a backing usually of cardboard or foam bonded to the aluminum with wax. 

During the induction process the wax is heated, melts and is absorbed by the backing, which remains inside the lid and allows the product to be sealed by seals for bottles when the container is closed once the aluminum has been removed. When working with aggressive or volatile products, a barrier layer can be included to act as a barrier between the heat-sealing layer and the foil.

There is also a two-piece seal that combines a higher containment barrier and the foil seal. The backing of this seal has a polyester foil in order to provide better oxygen permeability and better vapor or moisture transmission once the seal has been removed.

Finally, the removal characteristics of the seal must be determined. Does your application require a seal that will not leave seal residue in the mouth of the container when removed? Does your product require a seal that will weld to the mouth of the container or leave evidence of tampering and must be destroyed upon opening? Or do you require an easily accessible seal, which can be opened by pressing it with a finger or knife?

How to determine a good seal

While there are no industry standards for testing seal integrity, there are several ways to determine seal quality. Among the most effective methods are vacuum testing, dispensing/transporting the product to see how it responds, visual systems, mechanical pressure, shaking, squeezing or standing on a sealed container.

There are also certain characteristics that, at a glance, show us that we are in front of a good seal, such as a non-faded seals for bottles, adhesion along the entire circumference of the mouth of the container, a minimum seal crease and in two-piece seals, the latter is not obscured by overheating.

It will be beneficial to have a diagnostic process based on the information provided in this article to identify and resolve any of the problems with induction sealing, as many of them can be avoided by establishing quality control procedures on closures and containers, controlling the storage climate, conducting inventories, etc.