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How do I remove a stopper that has been stuck in the neck of a 100 mL round bottom flask since I forgot to wipe the neck of the flask. A salt was formed in the 100 mL flask and the stopper is just stuck like cement. Is there anyway to remove it without breaking the flask, breaking the stopper, or heating the flask (since I don't want to interfere with the product)?

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4 Answers 4

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Is it a hollow glas stopper?

Sometimes, it helps to hold the flask at the body and hit the corner of the lab bench with the stopper. If that doesn't help, heat the neck of the flask carefully with a heat gun.

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    $\begingroup$ No, it was a solid glass stopper. I tried the hitting method and it worked like a miracle. $\endgroup$
    – user9974
    Commented Mar 3, 2015 at 22:45
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    $\begingroup$ @86BCP2432T I'm glad I could help! Btw, when silicone grease is not an option - and sometimes it isn't - teflon sleeves are a good alternative. $\endgroup$
    – Klaus-Dieter Warzecha
    Commented Mar 4, 2015 at 6:31
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    $\begingroup$ While @KlausWarzecha provided the working solution, I offer up my own adopted mantra for future reference. "Most human problems can be solved by an appropriate charge of high explosives." $\endgroup$
    – LordStryker
    Commented Mar 4, 2015 at 14:29
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    $\begingroup$ When I was younger I worked at a place which had a serious accident which could have been fatal. Someone tried to open a flask containing pet ether using a flame to heat the stuck ground glass joint holding the stopper. I tend to use the hitting method on a wooden surface, use many gentle taps and keep on turning the flask around. I never use a modern plastic type lab bench. This method deals with most stuck joints on flasks and bottles. Never use a flame on glassware to free a joint until you have removed all flammable solvent from the glassware. $\endgroup$
    – Nuclear Chemist
    Commented Apr 15, 2018 at 20:13
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Here is an alternative that worked like a charm for me. I have a wide-mouth lab jar with a thick, ground glass stopper that stuck tight. None of the other methods worked; oil, heat, tapping, etc. I had an aerosol spray used to blow dust from computer keyboards/screens (it is not compressed air but a liquid that becomes a gas as it is released - i.e. the can gets very cold as you use it). A quick shot of cold gas directly on the stopper and it immediately shrank enough to easily come out of the jar.

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  • $\begingroup$ This is another reason not to use glass stoppers with separatory funnels. If one isn''t careful, pressure (from ether, CO2) can build up and the funnel may break. With a neoprene stopper one can feel the pressure as the neoprene stopper moves slightly. $\endgroup$
    – user55119
    Commented Jan 9, 2018 at 3:21
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Another easy method is to get 2 other glass stoppers and tap them on both sides of the neck of the flask firmly, sometimes this will free it up immediately, other times you may need to have someone pulling the stopper while you hit the stoppers on the sides

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  • $\begingroup$ I like the pulling while tapping. Requires more hands than the average lab worker has, tho. $\endgroup$
    – James Gaidis
    Commented Mar 31, 2022 at 14:14
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Had great success with the upside down can of compressed air! I had 2 small (10 mL) volumetric flasks with stuck PTFE stoppers. I tried warming the neck slightly but that didn't help. With the can of air, I placed the flask on the counter, blasted the cap just above the flask neck for a couple seconds, the tried opening and both came open right away! Awesome!

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  • $\begingroup$ +1 Nice to have a confirmation of a new technique. $\endgroup$
    – James Gaidis
    Commented Mar 31, 2022 at 14:15