We’ve had luck before with a 50/50 mix of water and solvent (we use ethanol), put a steel wool pad inside the glass with the mixture, plug the holes with anything from your hands to paper towels. Then swirl that around by hand for better control. If you can get the solvent mixture a little warm that will help too. Cleaning with the stir bar might work in this scenario but I highly recommend agitating by hand to ensure the steel wool and solvent mixture is making adequate contact with the stain. Good luck!
this works wonders, don’t leave it soaking for too long though - it works by slightly etching the glass surface.
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Right, good to mention that this will weld sintered glass shut and can eat away at important delicate structures in glass. Otherwise base blast it.
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Along the lines of aqua regia, this is another “at your own risk” option (that I do not suggest, but is sold by a reputable scientific supply company):
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I’ve used this before and it doesn’t do anything.
Update: I tried boiling the soapy water and it didn’t do anything. Debating on what to try over the weekend soak.
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You’ve used the flail and it was a fail?
Please define your surfactant more precisely Dr.
“soap” means way too many things to folks to be a useful descriptor here.
Yeah the flail doesnt work. Soap meaning like dish soap.
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USE. FUCKING. LYE
it say “NaOH” to stains
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agreed. 2mL of water for every 1g of NaOH or KOH. It will get hot AF when you dissolve it. Let er soak.
Whats the crude that was boiled in there
If natural thc etho extract > sugars > Noah
If alkane extract > gunk tolueen at a boil should work
Its BHO crude
Yust trow a liter of gasoline in there
It s got plenty of tolueen and xyleen in there to clean it then
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Would Shell V-Power NiTRO work better? Maybe fuel injector cleaner?
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Simple Green cleans just about anything off anything from my experience so far. Warm to about 60ºC, mix with some simple green and voila.
I have this I’ll look into it
I read online that lye might be bad for the glass. Going with good old fashioned alcohol for the weekend, which probably won’t do anything. When I’m back, I’m going to try heating the alcohol and mixing which I think worked the last time this happened after spending the whole day thinking about it and going through my run logs.
Rock salt and alcohol, swirl it around til gone
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Molten potassium/sodium hydroxide can dissolve glass, but that occurs at 300C. I get that stain a lot and it stubborn as hell. A lye solution of water usually works (with some ultrasound) but lye and alcohol should get you there.
You could also try and burn it out if all else fails and you have a big enough oven.
Toluene/xylene is also a good suggestion, very good for stubborn organics.
If all else fails, heat concentrated sulfuric acid and add 33% hydrogen peroxide (acidic hot pirhana solution). Be very careful because this is more corrosive than sulfuric acid, oh and this mixture is potentially explosive 
If it survives this then you deserve a Nobel prize.
Alcohol is a good option for most things because it has polar and non polar ends. Same as soap. But occasionally you’ll have things that are either really polar or really non polar and the alcohol just won’t cut it.
For example when we get wiped films in for repair the silicone oil heat transfer fluid in the jacket cannot be effectively removed with alcohol. We use brush cleaner from the paint section in Home Depot. It’s got mek, toluene, etc.
For sugars inside the wiper water works best. It takes a little scrubbing but it will work. Get all the cannabinoids out with alcohol then hot water will remove the sugars.
Sometimes some abrasion is necessary and you can use salt. I use the water softener salt with the huge crystals. This won’t really work with water but everything else the salt doesn’t dissolve.
Sometimes the fabric in the mantles has a little oil from manufacturing and that polymerizes on the outside of the flask. It’s basically like a plastic that is nearly impossible to remove. I usually just burn it off in our oven but I wouldn’t recommend that for anyone without a glassblowing oven. It takes really high temps and above around 400F your glass becomes stressed and will need to be annealed.
You can try acid. I usually use nitric acid. It’s really strong and smokes when you use it so be extremely careful. Wear all protective clothing, double gloves (not nitrile), apron, goggles, etc.
A base bath work also but not a whole lot better than just alcohol. It also takes a lot of alcohol and NaOH and it’s a pain to dispose of. Good for just throwing it in there for a few days and is sometimes the least laborious option.
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Piranha solution is another method… though I would highly advise you know WTF you are doing before messing with it. It can dissolve pretty much all organic material.
Including you.
Make sure to use proper disposal & PPE.
Very dangerous method if you don’t know what you are doing.
Follow ALL safety precautions, warnings, and disposal procedures.
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