Leaking Primary Packaging - Causes, Solutions, and Prevention

Leaking Primary Packaging - Causes, Solutions, and Prevention

To begin with, a word from the experts: a correctly designed and specified pack should never leak. Alright, that’s a bold statement – but we’re standing by it.

We do know, though, that there’s so much to understand around issues of this type. So, to start let’s look at some causes and how to prevent them.


Leaking pack for pharmaceutical or skincare product, oil on threads causing back-off of thread, find ideal closure torqueContainer and closure mismatch: there are so many standardised neck thread measurements, and matching them isn’t always as easy as it seems. While your best initial safeguard is – clearly – to use matching standard specifications for your container and closure, in practice it’s often tempting to go for slightly mis-matching ones, as often they will appear to fit. If you’re being dragged this direction, remember that it’ll be even more important than usual to thoroughly test your pack against all circumstances it might encounter.

Mis-matched H dimension: even with all the standardisation around containers and closure threads, it’s still possible to get a mis-match due to an adjustment in liner thickness (or another variable), causing an incomplete seal. Also, specifications that are on the edge – or just outside – of the stated standard, even when they initially appear to seal, can be a disaster if one of the components drifts to the other extreme of its allowable tolerance. Our team of packaging technologists is right here to do a desktop study on the tolerances of your chosen pack, before your pack starts going through the rigours of production and retailing or distribution.

Wrong liner/no liner: carefully selecting a closure with a suitable material and thickness of liner can make the difference between a great seal and no seal at all. And it doesn’t take much, very slight tweaks can make all the difference. Some liners may do a great job initially and then degenerate over time or due to ingredients in the product. Or, look at a boreseal, which has a flange which inserts into the bottle neck – if you pair it with a thick walled glass bottle, the diameter of the boreseal could be larger than the internal neck bore of the bottle, preventing the cap from screwing on properly. Liners and wads are there to seal the pack and are probably the most critical component to specify correctly, so just make sure you’ve got the right expertise allocated to this piece of specifying work!

Over-torquing: every closure has its own ideal torque, and it tends to be that the larger the closure, the higher the required torque – but over-do it and you could create a few other issues! Here’s our guide table to assist, though we want to make it clear that this is only a starting point, to help you on your way to finding the optimum through your own testing processes:

This is a reference point – don’t forget that different materials, formulations, and filling environments will all have various effects on the ideal torque you’ll need.

Reference table providing suggested closure torques for various sizes of closures - starting reference point for torque testing

Filling processes: the old ‘back-off’ issue is the oddest thing, the first time you come across it – how did that closure just unscrew itself? The secret to stopping this lies in clean, accurate filling. Get a drip or two of product on the neck threads, especially an oily substance, and you create the chance of back-off, where the friction is reduced and the cap slightly unscrews back from the ideal torque.

Formulation incompatibility: Essential oils with certain plastics is one of the most common examples of when your formulation isn’t compatible with the container or closure. Even though they’re 100% natural, they can cause softening of the plastic, producing worrying results - even destroying liners, eroding threads, jamming pump mechanisms… and more!

We can help you!

And our top piece of advice on all this? Make contact with our packaging technology team, because they actually enjoy helping to avoid issues like these before they get out into the market. Each pack that avoids all these issues is another successful product flying into the marketplace with a fighting chance of success!

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Preventions & Solutions:

Well... so far, so many problems. And at Richmond we don’t really like problems, we like to provide solutions and love preventing issues happening in the first place!

Clean Filling: yes, we talked about this already. Clean filling can be your key to maintaining good torque between the container and closure – so make sure you’re using high quality, well maintained filling lines for every product, to avoid that nasty back-off problem rearing its head just when you don’t need it.

Thorough Compatibility Testing: why does everybody talk about twelve-week compat tests? It’s because they’ve proved that there’s no substitute for a more extended test of your product in the pack. While these tests have a few different aspects to them, the extra time (sometimes even more than twelve weeks) to thoroughly check the suitability of the product for your package, is well worth it in the long run, when you’re reaping the benefits of a successful product in a reliable pack!

Real-Life Simulation: putting the product through as close to the real conditions as possible is essential. Working out how a pack will fare during transport, in storage, on the shelf, after purchase – it all needs to be taken into account. Some well-set-up drop tests will help you here too.

Vacuum Testing: if your product is going to get put through the stresses and strains of the real world, it’s nice to know how it’s going to perform beforehand, and at what kind of extremes it will begin to fail. Vacuum tests can ensure you have a pack to withstand the pressure needed – and you can test the effects of extreme heat and cold too.

In all of this, we're here to assist. Our packaging technology team always enjoy the challenge of creating technically winning packs to support growing brands, so by reaching out to them you can turn your nightmare project into a fun challenge, where you have support around you to assist you in creating something really successful. 

Mallaig bottle range - perfectly compatible glass skincare bottles with pipettes and closures