Best way to clean ya nasty boiling flask??

*Forgetful not lazy. I don’t think a lazy person would be doing anything that involves a glass boiling flask. Nonetheless, try to figure out how to clean a glass boiling flask.


any time i find myself doing something where I am making sure the first aid kit is next to me as a part of the SOP prep-
I have to stop and think “is there a smarter way of doing this that does not risk damaging my equipment or body?” if yes- I do that thing instead.

once you work your way up to reactions that generate or use reactive gasses, you’ll find yourself being more careful with everything you do, cause chemistry can and will kill the everloving daylights out of you in extremely unpleasant ways.

It is best to develop good habits early than try to unlearn them when you wanna play with the more delicate stuff, so handle all solvents as though they will hurt ya, you don’t wanna absentmindedly sniff the wrong flask yaknow?


Bad idea, it won’t seal like you think.

It’s not forgetting. How do you forget to clean your tools. It’s like saying a concrete guy forgot to empty the mixer barrel and it settled as concrete. It’s called being lazy and avoiding a responsible task. Always clean when done. Otherwise your just the same dude making excuses why a mixer drum is filled with solid concrete.


Just read about it. Pretty cool shit.

I swear to god I heard a chef use this exact same comparison when dealing with a new hire but he was screaming it at the top of his lungs.

That’s the difference between making a excuse about forgetting vs being lazy. Nobody likes stupid excuses.

You should be rinsing flask while its warm, it will clean it like new without any scrubbing needed. If you require scrubbing that means that you may have material inside the glass fissures and this means pre mature failure and implosion risk. Adding large joint like that means two things, you will have major leaks, and you will need apiezon h wich is not food safe and designed for flat surfaces. You will encounter a better performance curve without adding a “cuff joint”. (A 100/60 is considered a cuff joint). Not entirely high vac stable.

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If you put a room temp liquid in a hot bf, wont the bf shatter due to the temperature differences in the liquids?

Surprised I haven’t heard anyone mention leaving the stir bar spinning right after distillation, before the flask has cooled too much. Just add some solvent and move the flask around from time to time to hit the hard spots.
Any of these other methods can be used if it needs another round, but that should make the job a lot easier.


Why would I need to use the H one?
I use Apiezon PFPE 501.
How is a 100/60 joint any different from a 34/45 joint when properly greased?

So it’s one of those out if category joints. The next nearest joint that will hold proper vacuum easily is 71/60. I don’t Wana feed you too much info because I know you’ll just run off to china, but I can tell you now joints above the 55mm size tend to be problematic and it’s due to assembly procedures that bring the conical taper out of plumb/alignment. Typically (from a warranty and function) we see the need for apiezon h anything larger that will prevent leaks in those sizes. There’s a tool for every job. If you want to use the right tool to seal that kind of size joint you want to use apiezon h - anyways you might be better off doing a different cleaning procedure to make what you have work and last and much easier task.

Alot of people have a separate mantle I’ve seen, they let temps go down - and then add alcohol and in some time it’s all clean and dissolved refluxing from some time on heat.

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Immediately after you complete your run, i usually wait for the boiling flask to cool off to around 30-40 C to pour out its contents and then just spray the insides with iso, then cover the holes with some saran wrap, or just plug it with some paper towels and put it back on the heating mantle. The heat will evaporate the iso and make it recondense all over the insides of the flask, cleaning it in the process as it drips back down to the bottom. Acetone will usually get the rest of whatever doesn’t come out, but the iso by itself is usually all i need. You just gotta do it while the system is still warm, and it’s easy peasy.

Aqua regia is one thing, great for inorganic contaminants and quite good for organics. But if you want ultimate cleanliness from organic contaminants, you want what’s called piranha solution – h2s04 and 30% hydrogen peroxide. It fits the name and has fascinating chemistry such as the production of atomic oxygen as active cleaning agent.


My BF was stuck with some black sugar and it was stubborn to get off.I tried turning on my spd for hours boiling ethanol to try to steam it out. Then I tried putting it in hexane, acetone. Nothing worked. Turns out citric acid and ethanol works like a charm. Just need to rinse it out real well afterwards to make sure nothing is in there or it will mess up the ph of my crude. haha


When I worked in small molecule purification, we would clean our GMP glassware in a base bath. I think standard college SOPs call for dissolving a bunch of KOH in isopropyl alcohol and water and allowing it to sit overnight. If I’m not mistaken this actually begins to eat away at the glass surfaces and it is a super easy way to go full on fight club style caustic burns on your skin without a leather frock and elbow high gloves, oh and a splash mask. It’s not to hard toGoogle, look up base bath for glassware.


Please be safe. You need to have a DI or RO system on site to rinse your products off.

Note that this method can’t be used on fritted glass as it can fuse all the pores shut.

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Fritted disc buchner funnels, there is a trick.
Invert buchner funnel and put in a tray. Spray 99% iso into drain tube. Let gravity drain back out and it will be clean.

I posted this in the tricks of the trade a while ago.

Someone said acetone can also be used