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I am doing distillation using system of glassware including a flask and a glass joint. Recently I've faced a problem: the glass joint stuck in the flask. I tried to remove it but it broke and hurted my finger. I want to ask how to prevent this from happening again: can I use a paper masking tape or continue using grease? I am thinking to try the adhesive tape do you think it deserves trying?

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    $\begingroup$ Silicon grease on the ground glass joint. Use a heatgun on seized joints $\endgroup$ – Waylander Jul 10 at 21:07
  • $\begingroup$ Safety note: as you've apparently figured out, you should not apply heavy torque to a stuck glass joint with unprotected hands. Something like heavy leather gloves should be used. Also, welcome to chemistry.se. $\endgroup$ – airhuff Jul 10 at 21:25
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    $\begingroup$ Brings back the good old days in high school circa 1970. Used a lot of rubber stoppers and rubber tubing on glass tubes. Had to carry a pocket knife to cut them off lest you break the glass. can you imagine carrying a pocket knife into a school these days? $\endgroup$ – MaxW Jul 10 at 23:00
  • $\begingroup$ The next time try to use a wood handle of some sort or a wood rod to beat the joint. You won't risk injuries and very often it works. You can also envelope the joint/glassware in a cloth for maximum safety and if "energic" beating is required. $\endgroup$ – Alchimista Jul 11 at 9:09
  • $\begingroup$ I found, lying around my lab, a staple remover with the handle perfectly fitting between two jointed pieces of glassware. When two pieces get stuck, I press the handle, and they get apart with no effort. Rather than knocking the glass on a surface "the usual way", I would try to get creative and find something like that :D $\endgroup$ – The_Vinz Jul 11 at 11:41
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You have multiple options. All of them assume that the distillation setup is empty, at ambient pressure.

  • Of course, like mentioned in the comment by @Waylander, put a little of (silicon) grease on the glass joints prior to the distillation, just enough that they become transparent. There are multiple kinds of grease, suitable for different temperatures / pressures during the application.

  • If grease is not an option, there are sleeves made of PFTE / teflon to be put on the joints. They are available in different diameters, and forms, e.g.

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(source, source)

  • Especially for vacuum distillations, but not limited to this: the best remedy for this issue is to dismount the distillation right after the recovery of the product fraction(s), while the parts (e.g., column, head) are still considerably warm. Otherwise, once cooled to rt, the setup then often will stuck much better than ever intended. Depending on size of the distillation and remaining temperature of these pieces, wearing gloves (to protect your hands against the heat) may be helpful. Then, it is better to allow the warm pieces to cool to rt while being put e.g. on cork rings.
  • «Forgotton» and already stuck glass joints may be detached from each other if you immerse them in the basket of a ultrasound bath. Addition of some of detergent to the water bath helps while occasionally gently pulling the pieces apart.
  • If you have the dexterity (some develop this over time / by experience), wear both gloves to protect your hands against heat and goggles: you may heat the circumference of the outer wall of the glass joint with a heat blower or even a heat gun / pocket burner. The aim here is that the outer part of the joint dilates quicker than the inner part. It is the most risky variant because uneven heating may shatter your distillation into pieces; especially if the parts joined together are made of different types of glass with different expansion coefficients. It this is not for you, just ask your local glass blower for assistance.
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  • $\begingroup$ Dear Buttonwood, thank you so much for answering my question. I was just asking if a normal masking tape will tolerate such a high temperature and vapors during distillation but I think it will not and it will losses its adhesion and maybe will affect the joint this is what I want to make sure of. What do you think? $\endgroup$ – Shafik Saad Jul 10 at 23:55
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    $\begingroup$ Bad idea. This is not what the masking tape is designed for. You will also get the adhesive in your distillate $\endgroup$ – Waylander Jul 11 at 6:55
  • $\begingroup$ @ShafikSaad I second Waylander. Masking tape (by your comment) or adhesive tape (by your question) contain multiple compounds which the distillate might solute. At elevated temperatures, they may melt and drop into your flask; if they solidify they might glue your joints together, too. Each of these perspectives are counter-intuitive to the aim to purify (i.e., to separate) your target compound from other compounds. And even at room temperature, mechanically speaking, adhesive tape is not an alternative to a clamp to keep your pieces of a distillation joined. $\endgroup$ – Buttonwood Jul 11 at 17:09
  • $\begingroup$ @Buttonwood Many thanks for your help, I've bought a new flask and joint and I am using grease now and I am removing the joint immediately after distillation even if hot so I think I will not face this problem again, also I have a sonicator here and I've been told that a sonic bath with soap could solve it so I will give it a try... many thanks for your help $\endgroup$ – Shafik Saad Jul 12 at 12:16
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Silicon grease is the one we used normally. But, your post indicates that grease hasn't worked for you. Any adhesive tape wouldn't work because it will increase the risk of leaking (specially when you are refluxing). However, we have used PTFE sleeves between joints, which have worked wonders. These sleeves are not cheap but very durable and reusable. Following are the websites you can order them:

https://www.thomassci.com/Laboratory-Supplies/Stoppers/_/Sleeves-PTFE?q=Joint%20Ptfe%20Sleeves

https://www.thomassci.com/Laboratory-Supplies/Glass-Joints/_/TEFLON-SLEEVE-GASKETS?q=Joint%20Ptfe%20Sleeves

https://www.thomassci.com/Laboratory-Supplies/Glass-Joints/_/SYNTHWARE-PTFE-Joint-Sleeves?q=Joint%20Ptfe%20Sleeves

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  • $\begingroup$ Dear Mathew, thank you so much for answering my question. I was just asking if a normal masking tape will tolerate such a high temperature and vapors during distillation but I think it will not and it will losses its adhesion and maybe will affect the joint this is what I want to make sure of. What do you think? $\endgroup$ – Shafik Saad Jul 10 at 23:54
  • $\begingroup$ I would say the same. It won't tolerate masking tapes. $\endgroup$ – Mathew Mahindaratne Jul 11 at 19:24

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