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Author: Subject: Stir bar stuck! Help!
Mercurius
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[*] posted on 17-4-2012 at 13:02
Stir bar stuck! Help!


Ok guys, I've got a 3 inch egg-shaped magnet on the wrong side of a 24/40 joint in an expensive 3 liter flask. I really need a solution. I have some methods that have worked in the past and here is what i've tried so far.

1. Banging the joint on the ground with the magnet inside it.
2. Heating flask in oven, banging joint on the ground.
3. Cooling magnet in freezer, banging joint on the ground.
4. Making a suction cup with duct tape, attaching to a vacuum source and pulling.
5. Cutting duct tape into ribbon, looping the magnet, pulling through. (tape breaks)

Any solutions you guys have that I could try?!? For the love of god.
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Mercurius
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[*] posted on 17-4-2012 at 13:10


My next idea will be to fill the flask with water, stick the magnet in the joint, and to try and make a projectile out of it with steam pressure. Please stop me before I resort to that.
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gutter_ca
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[*] posted on 17-4-2012 at 13:19


Could you possibly be more clear about what the hell you mean?



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Mercurius
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[*] posted on 17-4-2012 at 13:22


The stir bar is in a 3 liter RB and will not fit through the 24/40 ground glass joint. It just gets stuck in the joint and won't come all the way out.

The objective is to get the magnet out of the flask, without breaking the flask.

[Edited on 17-4-2012 by Mercurius]
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Hexavalent
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[*] posted on 17-4-2012 at 13:30


How did you get it in there to begin with?



"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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inspector071
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[*] posted on 17-4-2012 at 13:34


Trying to use vacuum to suck it out sounds promising. I would be scared to try and pressurize it with steam. The only other thing I can think of would be a variation on a nifty parlor trick I learned a few years ago, used to get a cork out of an empty wine bottle. You take a plastic grocery bag, insert it into the bottle/flask so that you can inflate it like a balloon and catch the bag on the cork/stir bar, then pull it out. Here's a video of the trick. My main concern is that because it is a teflon coated stir bar, the bag wont have much to catch on unlike a large, grippy cork.
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gutter_ca
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[*] posted on 17-4-2012 at 13:41


Hex, that was my question exactly.

Mercurius, did you force it in there? Kinda a bad move! inspector071's bag trick sounds worth a shot.

Maybe try lubricating the flask neck?

Oh, and invest in a smaller egg! :D




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Mercurius
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[*] posted on 17-4-2012 at 13:53


Yeah, I had to force a little.. but not so much that I deserve this, lol.
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Endimion17
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[*] posted on 17-4-2012 at 15:17


Lubricate the joint and the bar with oil. Put everything in the freezer an wait an hour or two. Remove from the freezer and immediately apply preheated towel saturated with steam on the joint. Start removing the bar (you'll have to figure out how for yourself).
The point is to shrink the bar and to expand the joint. This actually works for glass stoppers which are forced into the dry joints.

For the love of FSM, don't use steam pressure. The flask will probably explode way before the bar gets out.
And do not ever bang the joint on a hard surface, it's too fragile.

IMHO, forcing the bar into a flask was a really stupid move. ;)




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RonPaul2012
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[*] posted on 17-4-2012 at 15:45


If you ever get it out and you insist on using the same egg , why don't you try grinding it down ;provided that the teflon is thick enough to allow a little bit to be taken off without affecting the performance.

What do you guys think ?
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Endimion17
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[*] posted on 17-4-2012 at 17:42


Grinding would create pores, and you don't want pores there.
If the teflon layer is thick enough (I doubt it), he could make it thinner by peeling some of it from the widest part, using a razor blade or a scalpel. Like a potato.




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Wizzard
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[*] posted on 17-4-2012 at 19:29


I like the bag/bottle trick, but you've got enough room to make sure the stirbar is IN the bag before you pull the whole thing out :D

Step 1: Get stirbar into bag, retrieve bag from RBF (by the handles/grips/edges).
Step 2: Lubricate!!!
Step 3: Cool the stirbar inside the bag with a cool liquid, so that it is submersed but not touching the glass. Maybe butane/CO2?
Step 4: Pull!

Also, one more idea, if it's very stuck:
Using the bag trick up to step 3, lodge the stirbar in the neck of your RBF. Drill it like a cork, and pull it out physically.

[Edited on 4-18-2012 by Wizzard]
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inspector071
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[*] posted on 17-4-2012 at 19:35


Quote: Originally posted by Wizzard  
I like the bag/bottle trick, but you've got enough room to make sure the stirbar is IN the bag before you pull the whole thing out :D

Step 1: Get stirbar into bag, retrieve bag from RBF (by the handles/grips/edges).
Step 2: Lubricate!!!
Step 3: Cool the stirbar inside the bag with a cool liquid, so that it is submersed but not touching the glass. Maybe butane/CO2?
Step 4: Pull!

Also, one more idea, if it's very stuck:
Using the bag trick up to step 3, lodge the stirbar in the neck of your RBF. Drill it like a cork, and pull it out physically.

[Edited on 4-18-2012 by Wizzard]


The way the plastic bag/bottle trick works is by the cork catching on an edge of the semi-inflated bag; the cork doesn't actually go into the bag, as that would be very hard to accomplish. The cork trick is pretty cool. It's always fun to impress friends and family with.
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Wizzard
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[*] posted on 17-4-2012 at 20:15


@Inspector- I realize that, but there's much more to fit with one squished rope of bag material, and a stopper, rather than a neatly folder bag wrapped around the stirbar. In a 3L flask, using some bamboo skewers or other tools, it would be trivial to put the stirbar in the bag before extracting it.
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inspector071
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[*] posted on 17-4-2012 at 21:06


Quote: Originally posted by Wizzard  
@Inspector- I realize that, but there's much more to fit with one squished rope of bag material, and a stopper, rather than a neatly folder bag wrapped around the stirbar. In a 3L flask, using some bamboo skewers or other tools, it would be trivial to put the stirbar in the bag before extracting it.


Good point, didn't notice it was a 3L flask. If he was able to fit it into the bag, it should be pretty easy to pull out, perhaps with a bit of lubricant on the neck. Silicone grease or something.
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Dr.Bob
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[*] posted on 18-4-2012 at 05:42


I can feel for you. I used to have that problem with the larger stirbars. For some reason that I can't fathom, they make the largest oval stirbars just bigger than a 24/40 joint. So I always take a scalpel or single edged razor blade and just trim the edges at the fattest spot a bit. It does not hurt the stirbar or make it less effective, I have been doing that for 15+ years.

That is also why I rarely use the larger stirbars as well, I find that most people use one that is too long. You are always better to use a smaller one than a too long one, as they will not stir well if they are touching the sides of the stirbar, you need the radius of the stirbar to be smaller than the flask so it only sits on the center of the oval.

Is for getting it out, often it is just a matter of trial and error to find the right orientation of the stirbar to get it to come out, but cooling it will help and then warming the flask neck. But I can tell you it is very difficult to succeed at getting them out once they are swollen with solvent. (Yes, Teflon stirbars absorb solvent slightly, especially DCM and other chlorinated solvents.) So the other option is to put the flask under vacuum for a day or two to try to remove the solvent from the Teflon, but not sure that will do enough to let it just fall out. The other solution is what many people do once this happens: leave the stirbar in the flask as a dedicated stirbar for that flask. I have seen some stay in a flask for years of usage.

Best of luck.
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dann2
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[*] posted on 18-4-2012 at 06:07



A variation on the 'drive it out with steam' method.
Place a small amount of ether in the flask and then jam the egg in the neck and heat a bit. Its sound more gentle than the steam. It will have to be air tight for this to work which it probably is not. Is there any way you can make an air tight seal behing (on the inside) of the egg.
The ether stuck to the sides of the flask should be enough to create a mild pressure.
Finding some way to form an air tight seal behind the egg is the problem.

A variation on the bag method would be some fishing gut (very thin string). If you can make a circle of fishing gut with three or four pullers and get the egg sitting into the circle using thin sticks.
Easier said than done I guess.

Leaving the stirrer in the flask can be a risky thing as when you are washing the flask you must never give it a shake as the egg will knock the bottom out of the flask far quicker than you would imagine.

Dann2

edit
Have you asked the flask to pushharder? . PUSH HARD PUSH HARD

Mop the flasks head with cold water..............

egg.GIF - 2kB

[Edited on 18-4-2012 by dann2]
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[*] posted on 18-4-2012 at 06:23


Air-ether mixture in a 3 L flask? dann2, are you out of your mind? He might as well put some nitroglycerine inside. :O
One static electricity spark and there'll be a detonation of glass shards.

If he chooses to try such procedure, he should use dichloromethane, not ethyl ether.




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Dr.Bob
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[*] posted on 18-4-2012 at 07:24


Those tricks won;t work for the Bel Art stir bars, as they are not smooth, they have slight ridges like the seams of a football or a hexagonal stirbar, so you cannot build up any real pressure behind them. That is why it is easy to fix them, because if you just shave off the high spots, the stirbar will now fit easily. But getting this out will not be easy. You have to shrink the stirbar, maybe even with LN2 and then try to keep the neck of the flask warm, which may crack the flask. The vacuum approach to shrink the stirbar is likely the safest approach to try. Using DCM to try to expel the stirbar will only swell it more.
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dann2
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[*] posted on 18-4-2012 at 13:20



If the bar is not round as you say then the strings (fishing line) should work OK. The finshing line can be taken out between the egg and flask neck in places where the egg is not tight against the glass.

People have gotten ships into bottles you know :P
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Dr.Bob
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[*] posted on 18-4-2012 at 19:17


Yes, it might work. I meant to say the tricks with pressure, as the idea with the string, fishing line, or even dental floss might work. Try glide, it is very slick. But I actually cracked a joint on a flask when I tried something similar once. I may have just had an uneven pressure, however.
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Mercurius
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[*] posted on 20-4-2012 at 00:01


Well, you'll be happy to know that I haven't tried to build the flask-magnet-gun quite yet, but I agree with it's vapor pressure that DCM would be the best solvent to accomplish it. In combination with the bag method it would put a tight seal around it too. However, I feel like getting the magnet stuck is still a lot easier to explain than a uhhh.. "rapid decompression" in the hood.

So, this isn't my first rodeo with stuck stirbars.. I do always cut the ridges off the egg with a knife, unfortunately it's still stuck in there good. I tried every combination of cooling the magnet and torching the flask neck and repeatedly trying to find just the right arrangement to have it fall out.. to no avail. I've lubed up the flask neck with silicon grease and even gave astro-glide a shot, in combination with the other methods, still no luck.

Tried the bag method, and I have to say it's quite ingenious.. it does seem like in other circumstances that it would work.. the magnet catches and enters the flask neck. However, I encountered the same problem I did with the duct-tape loop.. the material tears before it pulls through.

@Dr. Bob I liked your answer the best, I had not considered that the teflon would have become solvated and expanded, and in fact I had been working with some DCM. This seems likely and I'll give the vacuum idea a go when I get the chance, and then try these other methods again. As a last resort, I wonder what might be hanging around the lab that would dissolve the teflon? I've had reactions that have melted the teflon right off of the magnet before, leaving a cylindrical core.

Until then, I dub thee my stirring-flask combo.
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[*] posted on 10-5-2012 at 18:16


So I put a stirbar into a flask and had to push it in. Then I remembered this thread, oh damn! The stirbar was indeed stuck inside the flask.

I cleaned out the flask then half filled it with water. Shaking it up and down was enough to pop it back out!




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[*] posted on 15-5-2012 at 15:21


If you can get the joint submersed in an ultrasound cleaner you should be able to combine vibration with soapy water. Friction is holding it in. Break that and it will slide out. IMHO heating will expand the stir-bar more than the glass but you could try a directed stream of cold CO2 or a piece of dry ice against the stir bar followed by hot water on the joint.



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