Thoughts and News on High Visibility Packaging

July 20th 2009, Clamshell, a double blister with card inside

The best theft protection for retailers, but in many cases a nightmare for consumers to open.

Clamshell blisters, are extremely popular with retailers due to the fact that there is almost no packaging that gives better protection against in-store theft. To increase the theft protection of clamshell blisters even further, very often security labels such as HF or ultrasonic alarm tag labels are positioned inside the plastic packaging. Unless customers are equipped with scissors or a knife, this kind of packaging is extremely difficult to open in the store thus giving the best protection against pilferage.

clamshell blisters

The downside of extremely good theft protection is that, once at home, clamshell blisters are very hard to open, even when using a knife or scissors. Unfortunately many cases are known where customers get injured while opening clamshell blisters.

 Clamshell blisters are widely used to pack up-value consumer goods, sold in a DIY, or self selling (warehouse) environments. Products such as electronics, computer hardware, sanitary accessories, automotive parts etc. are often packed in a clamshell blister.


Clamshell blisters usually consist of a thermoformed front blister and a back blister (or flat plastic sheet) with a piece of cardboard or paper trapped between the blisters.

Depending on the size of the blister and the desired strength, the thickness of the plastic can be adapted to the specific requirement. The plastic is usually a PVC, PET-A, PET-G or PET GAG. The insert piece that carries the communication and product information is made of printed paper or cardboard.


Clamshell blisters can either be sealed, using high frequency sealing, ultrasonic sealing or simple heat sealing. The choice of sealing depends on the type of plastic that is being used.
In case PVC, PET-G or PET-GAG (Glycol modified polyethylene terephthalate) is used, it is possible to use induction or radiant heat sealing. The best heat-sealing results can be achieved in case the patent pending hot-cold technology is used. The advantage of this hot-cold technology is that the sealed blister flanges will not become brittle and that they will become flat and strong after sealing. Conventional heat sealing is possible, but expect blister flanges to become a bit brittle and curled.

In case A-PET is used, high frequency sealing or ultrasonic sealing are the best sealing techniques.

 Reclosable Clamshell blisters

It is also possible to choose a fold-over type of clamshell blister that can be closed, simply by clicking the front and back blister together. This type of clam shell blister is very popular as no machines are needed to close the pack. Also opening and re-closing for demonstrating a product is simple to do.


A clamshell blister is very suitable for recycling. The two materials, card and blister are not bonded together. The paper part and plastic part of the package do not contaminate eachother and can be disposed separately in the according waste streams. Some consumers may dislike this kind of packaging, because of the large plastic part, but an alternative packaging with the same properties is often hard to find. The plastic part should have a material identification marking, pet recycling logoindicating which type of plastic is used. This is done to enable consumers to choose the correct waste stream. In Germany and some other countries packaging taxes are very high when using plastic.


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