Sciencemadness Discussion Board

Sealing ground glass - Glindemann rings (PTFE) vs sleeves vs grease?

RogueRose - 24-7-2018 at 09:33

So IDK how I stumbled across this page a few days back, it looks like it was made by a "mad scientist" but he is marketing something called "Glindemann Rings" which are extremely thin and narrow rings/bands of PTFE that slide onto your glassware to create an air tight fit. When I say thin and narrow, they look thinner than a piece of printing paper and maybe 1-2mm in width.

here is the inventors site:
http://www.glindemann.net/business.htm

Now I can't find a distributor in the US other than Sigma and they want almost $55 for 50 of these rings, which if they work as well as they claim MAY not be a bad price, especially if reusable.

The claims are that these will make a perfect vacuum seal on ground glass joints. On acid reagent bottles with glass stoppers, they will stop the gasses from leaking and corroding everything in a 30ft radius (the 30ft is my claim...).

looking at some pictures it looks like you are getting about $.25 cents worth of PTFE, maybe less, but I'm sure they have to be a very exact thickness for this to work. I also think that the price is high because Sigma is selling it, maybe they are less in the EU (where he is located) as there looked to be about 30-40 distributors.

I also came across some PTFE sleeves on some glassware I bought and they look promising but I have yet to use them in a setup. I haven't seen pricing with these yet.

Then there is grease or using something like sulfuric acid as a lubricant. IDK how much I like the idea of SA (I'm guessing fairly high concentration, so it is thick??) possibly leaking into the glassware under vacuum - it may not be bad if distilling KNO3 from a SA/nitrate mix, but otherwise, IDK.

So that leaves grease, some mention silicone, others mention vasoline. I have 2 large Buchi condensers that have a total of 8 stuck joints (must have been why they were getting rid of it) that look like some kind of tan/brown grease was used to keep the joints from locking - didn't work.


So, when looking at the possibility of having stuck glassware and the potential for breakage, an investment in PTFE sleeves or rings/bands seems that it may be a good idea.

I'd love to hear some feedback on the Glindemann rings especially and others take on what their favorite agent is for non-sticking joints.

On a side note, the website for the rings looks as if a mad scientist created it. I thought that these things might have been a fraud at first when I saw the layout of the page, it's worth a look just for the entertainment value!

arkoma - 24-7-2018 at 09:55

One inch wide PTFE tape. Plumbing stuff.

Dr.Bob - 24-7-2018 at 17:01

I have not used his PTFE rings, but tried many PTFE sleeves. Most are too thick and don't seal well. But some work fine.

One trick you could do is to buy a few thin PTFE sleeves and then slice them into thin slices, thus creating your own "rings". Many greases eventually seize, but often they can be loosened by heating strongly and carefully, but a good glassblower can often unfreeze them. You can try to unfreeze them yourselves, sonication can also work. Many tricks exist to try, but all have some risks. But frozen joints are pretty useless, so I just keep trying things until something works or I break it.

BromicAcid - 24-7-2018 at 17:31

The Glindemann Rings work great, always been a fan. Regarding conc sulfuric acid though, I've only seen it used as a lubricant when distilling perchloric acid.

RogueRose - 24-7-2018 at 17:53

Quote: Originally posted by Dr.Bob  
I have not used his PTFE rings, but tried many PTFE sleeves. Most are too thick and don't seal well. But some work fine.

One trick you could do is to buy a few thin PTFE sleeves and then slice them into thin slices, thus creating your own "rings". Many greases eventually seize, but often they can be loosened by heating strongly and carefully, but a good glassblower can often unfreeze them. You can try to unfreeze them yourselves, sonication can also work. Many tricks exist to try, but all have some risks. But frozen joints are pretty useless, so I just keep trying things until something works or I break it.


Thanks for the ideas! The slicing of the sleeves is worth a try for sure as I plan on buying some either way. Ordering the 50 rings was close to $78 with shipping or so, for the amount of material that wouldn't even make up one standard 24/40 sleeve! Talk about profit margin, lol :)

So has no one here ever used these rings? From the one chemistry forum/blog I was on, it sounded like they are ubiquitous within industry, which seemed odd since I had never heard of them (not that I know all, FAR, FAR from that), but I've read the Fischer, Spectrum, VWR and Sigma catalogs (the THICK ones like 3000+ pages) and I never came across these things.

As for the PTFE tape, I've considered that but I have heard they very often lead to seal failure especially under vacuum. all it takes is a slight mis-alignmnet and your screwed, or maybe the tape slips. That stuff doesn't stick to anything to begin with, then when you try to wrap a male end and slide it into the receiving end, I can't see how it would adhere to the male end. Are there any tricks to this?

Herr Haber - 25-7-2018 at 04:32

Quote: Originally posted by RogueRose  

I've read the Fischer, Spectrum, VWR and Sigma catalogs (the THICK ones like 3000+ pages) and I never came across these things.

Perv! :cool:
Quote: Originally posted by RogueRose  

As for the PTFE tape, I've considered that but I have heard they very often lead to seal failure especially under vacuum. all it takes is a slight mis-alignmnet and your screwed, or maybe the tape slips. That stuff doesn't stick to anything to begin with, then when you try to wrap a male end and slide it into the receiving end, I can't see how it would adhere to the male end. Are there any tricks to this?


First thing first: I love sleeves. I have many 19/26 and many more 24/40
I have thin sleeves (wonderful) and thick sleeves that I'm still wondering what to do with.
I first got some for my Duran glassware (19/26). Of course, Schott makes much much better quality glassware than... Deschem and the sleeves were barely needed.
But still, I liked having the sleeves as this Duran glassware is Rodaviss and wouldnt want to find spares for the plastic parts and Viton rings!
With good joints and PTFE sleeves frozen joints are history.

They dont work as perfectly with my chinese glassware. Or better put: it works. With the German glassware it's a bonus in safety.

I understand that those Glindemann rings would get squished between the 2 joints to provide a seal.
I suppose it's interesting though not life changing. Maybe if I had to work with vacuum or pressure then I'd be more interested.
And finally, plumber's tape is great.
It slightly stick to itself so wrap it around your joint and overlap. Insert by twisting stightly so it stays in place.

RogueRose - 25-7-2018 at 10:50

Thanks for the reply. Yeah, those catalogs are kind of like chem porn and it is a good place to learn about things that you might never other wise come across or see. I try to ignore the pricing but use them to see what is available for the most part. IDK if they still ship catalogs upon request like they used to, I ordered them when I was a private individual (no company affiliation) and all of them shipped w/o question. Now when I submit a request (even with a research website business listed as "business") I haven't gotten a catalog from one company since. It seems odd IMO. It's SO much easier to browse cat's than websites for so many different reasons.


It's nice to know that sleeves/rings may not be needed with good glassware as that is what most my stuff is, though I was about to make a big order from Deschem (may reconsider and look for used quality stuff).

I'm most worried about running under pressure or vacuum which I think the sleeves or rings might be a necessary evil for piece of mind while running the experiment. There is nothing worse than being in constant fear/worry that there is going to be a failure in the joints while working with toxic chems and especially gases.

akmetal - 11-1-2024 at 23:56

Does anyone know where to buy Glindemann Sealing Rings for Jointed Glassware. Trying to buy from Stuart lab group was frought with issues and I eventually had to get a refund.

I just ordered from Sigma but it looks like I'm going to need a national security clearance to basically order some rubber bands lol.

[Edited on 12-1-2024 by akmetal]