I have a sintered glass funnel stuck in a flask with a 24/40 ground glass joint.

I regularly used this glassware to process very dilute solutions of uncured photopolymer resin dissolved in ethanol. Unfortunately, I believe I accidentally hit the joint with some stray UV laser light while it was wet, thus curing some of the resin, and binding the glassware together:

enter image description here enter image description here

Because it was so dilute, combined with the flask being under vacuum, I guess it was able to work its way well into the space in the joint.

I already consider this glassware to be lost; it's been in storage for a while and now I'm cleaning house. Still, I figure I'll go for one more Hail Mary attempt at separation before trashing it.

What's my best chance for separating these? Is there something I can do with heat, or a solvent besides ethanol, or some other trick that might help?


  • I've got all the necessary PPE to apply brute force if needed. However, I do not have a fume hood or a lot of lab experience, so things like e.g. hot piranha solution are aren't an option for me. My setup is wood / metal shop, not so much chemistry lab.

  • The only thing I tried when it originally got stuck was soaking the joint in ethanol for a while at room temperature, hoping to dissolve any resin; but it didn't work; or at least, it didn't separate with the max amount of force I was comfortable exerting (with gloves on) before I felt it would break.

  • If all else fails, then I'm going to cut the top of the flask off and grind everything down mechanically to try and recover the funnel at least. I want to try to save both, first, though.

  • 2
    $\begingroup$ Maybe using acetone and an ultrasonic bath. For a day, and with plenty of ventilation. Good luck! $\endgroup$
    – Ed V
    Commented Oct 26, 2021 at 17:10
  • 1
    $\begingroup$ @EdV That is a great idea and, frustratingly, my ultrasonic cleaner is barely too small to accomodate the glass. I'll think about this a little though, maybe I'll get some inspiration. Or maybe I know somebody with a larger capacity cleaner. Thanks. $\endgroup$
    – Jason C
    Commented Oct 26, 2021 at 17:13
  • 1
    $\begingroup$ I would recommend putting it in a soap bath for a few days and then heating the joint with a hot air gun or blow dryer. I've done this a couple of times, and it seems to work fairly well -- although it might take a while! $\endgroup$
    – Eli Jones
    Commented Oct 26, 2021 at 18:19
  • 1
    $\begingroup$ After you get these unstuck, your metal shop comes in very handy: just make a PTFE sleeve for future use between the filter and flask. Or buy the inert adaptor, maybe! ;-) $\endgroup$
    – Ed V
    Commented Oct 26, 2021 at 21:57
  • 1
    $\begingroup$ Seek a professional glass blower. While these become more and more rare on campus of a research university for specialized glass ware you can't (yet) purchase from a catalogue for chemistry and physics, these have large baths and the experience e.g., to flame heat just the outer neck of the flask to disentangle the connection. Or contact a manufacturer (e.g., Chemglass). With standard lab equipment, however, curation by UV across glass is less likely than getting stuck by aged grease, reagent alkalinity, or cycles of heat and (ambient) cold. $\endgroup$
    – Buttonwood
    Commented Oct 26, 2021 at 21:59


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