Lid stuck on vacuum desiccator

[senjoronie]

This seems, to me, a somewhat silly topic, but alas the problem is real. Maybe it's never happened to anyone else, because after searching Google, E&W, and Science Madness, I've found no information that even remotely addresses this problem.

I have a vacuum desiccator whose lid is stuck on and there isn't anything that I've been able to do about it. It's one of the heavy glass Pyrex brand desiccators which uses ground glass flanges to fit the lid onto the desiccator body, and it's sealed with the standard-issue Dow Corning high vacuum grease. The grease is quite fresh, as I removed the old, dirty grease and replaced it before pumping the air out of the chamber.

Well, after letting the air back in (the top valve works fine) I tried to open the thing up, but found the lid to be stuck fast. I put as much force on it as I was able, trying to sliding the lid off normally, but it wouldn't budge. I even tapped it a bit with a soft rubber mallet, but no luck there. I tried heating it by running hot water over it, thinking that this would soften the grease, but no dice there either. I have not tried wedging the two halves apart and probably won't, because in my experience, putting any serious force on glass will just result in breakage.

But at this point, what else is there to do? I'd like to avoid breaking it open if possible, but I'd also like to get my samples and their containers back. I don't know. I've had glass joints get frozen/stuck before, but I've never heard of a desiccator lid getting stuck. Maybe I should have used some kind of gasket between the body and lid. If that's the case, then lesson learned, but how can I get the lid off so I can apply the lesson in the future?

[Hinckleyforpresident]

Any way you can hook it up to a air compressor or the like? Maybe raising the pressure inside would cause the lid to pop off.

[Hirudinea]

Mabye you could try heating the rim of the vessle with a hand held torch (I don't know what the rim is like, but if just glass it should be able to take it) while at the same time cooling the lid with a container of ice, could work.

[megalomania]

Although I doubt your dessicator will fit in a lab oven, you may want to cook the thing at a low heat in a domestic oven for an hour to soften the grease. Using shims of narrow metal, like razor blades, slowly insert them and work them under the gap. If you can wedge enough blades between the gap it should loosen enough to break the seal. Something larger and thicker, like a putty or spackel knife, could be tapped in for levering action. I don't recommend a screwdriver because you may well crack the glass. The putty knife is flatter and distributes the force over a larger area.

[FUTI]

Hair drier rocks. If I understand well your problem grease is hardened between the lid of dessicator. Heating with hair drier usually works for me. I wouldn't use blowtorch those things are made from thick glass, if you heat them to much it can't stand thermal expansion and *crack* - now you have one dessicator less and those things are fu*king expensive. Compressor is better idea but if you can limmit the pressure so it won't turn your dessicator into glass shrapnel granade, and even if you can do that those grease seals are bitchy...they won't go, they won't go and then you find yourself loking for the upper part pieces of that dessicator somewhere on the ceiling. Another advice I have is to try first to use small amount of petroleum added drop by drop on the lower rim(flange?) of that dessicator with some pasteur pipet (or droper?). Capillary forces should draw petroleum inside between the flanges. That maybe soften the grease a little although I use that little trick when ungreased groung glass joints freeze more often. Hair drier always worked for me with dessicators. HTH

[senjoronie]

Well, at least this situation ended well. Thank you all for your advice. I managed to get the lid off by blowing as much air as I could into the desiccator and then closing the top valve. The pressure couldn't have been more than a couple PSI, but spread over the lid's area it can add up to a lot of force. The lid came off some hours later, after the pressure gradually worked its way into the seal and loosened it. I bought a rubber O-ring gasket that should prevent the lid's getting stuck again.