Do you have a stuck glass joint?

Have a question about lab glassware? Here at Radleys, we’ve been scientific glassblowers for over 50 years, so we’re in the perfect position to help you with your glassware queries.

As part of our blog series inspired by our product FAQs, this week we will come to your aid and rescue that frozen glass joint!

Oh no! My joint is stuck …

A seized joint is a common problem when working with standard ground glass joints – you’ve finished your experiment, go to separate the socket and the cone, and find they will not come apart! Most of us have experienced this in the lab at one point or another. So how can you avoid the frustration?

Preventing frozen glass joints

As with most things, prevention is better than cure.

When using standard ground glass joints, some common advice is to grease the joint, or to use PTFE sleeves.

Greasing the joint (between the sealing faces) can help, but the grease may dissolve in your solvent or make its way out of the joint during your experiment. As well as potential contamination to consider, the joint may still freeze despite your efforts.

PTFE sleeves are thin pieces of PTFE (a very chemically resistant plastic), which fit between the socket and cone to try to prevent sticking. If, however, you’re using precision-engineered glassware, where the dimensions are exact and you can’t add extra height to the set-up, this would not be recommended. You might also find you can’t reach desired vacuum levels when using some types of PTFE sleeves.

Alternatively, Radleys offer advanced joint designs that make it less likely that the joints will stick.

Rodaviss joints (below left) are used on most of Radleys glassware, such as between Carousel 6 Plus flasks and reflux tubes. They are based on a standard ground glass joint, but include a screw thread on the socket and a screw cap on the cone, together with a glass rim and plastic loosening ring. What’s the significance? As well as being able to secure the cone and socket together, to separate them you simply unscrew the cap back onto the loosening ring, which pushes the joints apart.

Rodaviss jointWide neck round bottom flask with reflux tube

For wide neck Carousel 6 Plus flasks (above right), we use a flat flange design with O-ring and coupling. Again, this makes it easy to separate the two glass parts.

Separating stuck joints

The tips above should minimise the risk of your glass joints sticking, but the issue can’t be completely prevented. Sometimes your particular application (chemicals etc.) can cause stuck joints.

If you look online, you will find a variety of suggestions to separate your joint. However, some of these can be dangerous, with warnings of injury or even death! Remember that glass – even the high quality borosilicate glass 3.3 we use at Radleys – is relatively fragile. Although some methods involving force (such as knocking the glassware on the edge of the bench) may work, it’s best to avoid them if possible, due to the risks.

If you can empty your glassware of chemicals before separating the joint, then safe ways of separating stuck joints include using a suitable solvent or lubricating oil to dissolve chemical residue in the joint, soaking the joints if required, and/or using a sonicator or ultrasonic cleaner. Or, you could use temperature to contract or expand the glass – some chemists put their glassware in the freezer; others carefully apply heat to the outer socket.

Whichever method you choose, you should always consider your chemistry, and ensure any actions you carry out are safe for your specific set-up.

The right equipment for the job

As mentioned previously, the best way to tackle the annoyance of stuck glass joints is to prevent them from occurring in the first place – and often, it all comes down to the equipment you use. Radleys glassware, like the Carousel 6 Plus range, use advanced joint designs that minimise the effects of sticking – so if it’s a regular issue, you might want to consider switching.

[Learn more about the Carousel 6 Plus]

Get in touch
Any other lab issues you’d like us to troubleshoot? Our product FAQs is full of answers to common queries, or you can talk to our technical specialists by using our online live chat, emailing or calling +44 1799 513320.