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Grip Seal Polythene Bags or Self Seal?

If you’re struggling with how to seal polythene bags, you’ve probably considered using a self seal solution. But there’s more than one way to seal a bag – and the options might be overwhelming. What’s the most secure and reliable method? Which type has the most tamper-proof seal? And what’s the most cost-effective solution?

Two popular choices are grip seal bags and self seal – but what exactly sets them apart, and which one is best suited for your needs? Let’s take a closer look at the most common types of self sealing bags, and why some are better suited to some tasks than others.


A grip seal polythene bag with a CPU inside, on a vivid, highlighter yellow background. The image is intensely bright. The CPU in the grip seal bag is an Intel Core i7, marked with black Sharpie. It sits nearly upside down in the grip seal bag, at a jaunty angle. There is a red stripe above the grip seal, which is very stark against the vivid yellow backing.


Grip seal vs. self seal: what’s the difference?

By name alone, you might be thinking “same thing” – right? Well, yes and no! Both are polythene bags with sealing mechanisms built-in, but the way they do this is rather different.

Grip seal polythene bags

Grip seal bags are more colloquially known as Ziploc or “sealy” bags, and feature a resealable closure mechanism: basically, a plastic strip with interlocking teeth. Users can press the strip closed to create a secure seal, and then easily reopen it by pulling the strip apart.

Self seal polythene bags

Self seal bags, on the other hand, typically use an adhesive strip on one side of the bag opening, sometimes on an extended flap that folds over. This is a one-way street, though – once the user has sealed the bag shut, the bag remains closed until manually opened. The seal is often so tight that the bag has to be torn in order to get the contents out.

That’s not necessarily a bad thing, though.

Why use self seal polythene bags?

Self seal bags allow for quick and easy sealing, without the need for additional equipment or accessories. They are also far more tamper proof than standard grip seal bags, making them a better choice for clothing, medical packaging and pharma packaging. Heavy duty self seal bags can also be applied to hazardous waste disposal – shielding the user from the harmful contents.

Self seal bags offer convenience and ease of use, allowing for efficient sealing without the need for additional sealing equipment. This makes them cheaper and less labour-intensive than using sealing machines or forming your own bags with layflat tubing.

But while self seal bags have their place, they are quite wasteful for some applications – particularly in food packaging and other niches.

Advantages of grip seal polythene bags

Grip seal bags provide a secure and resealable closure, making them ideal for items that need to be accessed multiple times while remaining protected from dust, moisture and contaminants – and not just for food!

While we probably associate grip seal bags with keeping sandwiches and nuts fresh, they are often also used for storing and organising small parts – like hardware and craft supplies. In manufacturing, they can be used to ship additional self-assembly components in a safe and user-friendly package.

Their biggest advantage is their resealable strip, which makes them useful for far longer than their contents might be. They can be cleaned and used again and again, until they’re notched and no longer viable.

And their biggest drawback? Tamper-proofing is hard to achieve without introducing complexity; like a second heat seal above the grip seal, or perfectly aligned printing that shows when the package has been opened. Of course, it’s possible – just more complicated and less reliable than simply removing an adhesive strip and closing the bag.

Grip seal bags also use more material and weigh more. They can stack awkwardly unless the orientation is regularly changed – but this can be avoided with gusseted bags. And, although rare, the grip seal mechanism can fail, especially if the duty is above and beyond what the bag was designed for.

But even with these drawbacks, grip seal bags are brilliant reusable packaging options that can help users – and the planet.

Custom self seal polythene bags

NPF Packaging creates custom blended packaging products – including self seal polythene bags. Get a quote now, or call us on 01773 820415 to start your order.