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Author: Subject: Has anyone used plumbers TFE paste / joint compound for glass joints?
RogueRose
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[*] posted on 13-3-2019 at 00:04
Has anyone used plumbers TFE paste / joint compound for glass joints?


I was at the hardware store and they had a few different products, one was a "90% silicone grease" and the other was a TFE paste/joint compound. I think the price was cheaper for the TFE, maybe 1/2 or 1/4 the price, so I held off on getting any. The stuff does contain PTFE

https://www.amazon.com/Harvey-023045-Pint-Paste-Teflon/dp/B00004SWKE


I think the temp rating for the product at the store was 400F, which seems pretty high, and says it liquifies at 500F (would be nice to find out exact #) IDK if silicone grease is higher.

The label from the link does say that it doesn't harden, so that seems like a good thing especially if it is $10 for 8oz of product.

This looks to be the same thing, but smaller size and available at Ace
https://www.acehardware.com/departments/plumbing/solvents-and-cements/plumbers-putty-and-sealers/4396321


Upon looking at the silicone grease, it's rated at 400F as well.

Has anyone tried this PTFE based compound? I'll probably buy some and test it out unless someone has already tried it and it didn't work, I don't want to ruin glassware.
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Sulaiman
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[*] posted on 13-3-2019 at 00:25


I just want to mention that I've mostly changed from silicone grease for sealing ground joint glassware - to plumbers ptfe tape,
a single-width winding of a few turns on the male part;
. works really well to seal,
. does not form tar when exposed to halogens as silicone grease does,
. is easy to clean up compared to grease,
. does not dribble grease into the reaction vessel when hot,
. makes Keck clips a little tighter,
. allows a tiny bit of 'wiggle' - useful for larger glassware setups where a spherical joint would normally be used.

So far I've not found a reason to use silicone grease for glassware since using ptfe tape.





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UC235
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[*] posted on 13-3-2019 at 02:44


Quote: Originally posted by Sulaiman  
I just want to mention that I've mostly changed from silicone grease for sealing ground joint glassware - to plumbers ptfe tape,
a single-width winding of a few turns on the male part;
. works really well to seal,
. does not form tar when exposed to halogens as silicone grease does,
. is easy to clean up compared to grease,
. does not dribble grease into the reaction vessel when hot,
. makes Keck clips a little tighter,
. allows a tiny bit of 'wiggle' - useful for larger glassware setups where a spherical joint would normally be used.

So far I've not found a reason to use silicone grease for glassware since using ptfe tape.



Yeah, but it has to be a single layer only, evenly wrapped, and not forced too hard into the other joint if heating. I broke several rbfs while using multi-layer tape, and heating before I figured it out. Coefficient of thermal expansion is much higher than glass.
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Sulaiman
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[*] posted on 13-3-2019 at 02:47


I'll keep that in mind ... thanks



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Arthur Dent
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[*] posted on 13-3-2019 at 11:23


I use silicon dielectric compound, similar to this: https://www.walmart.com/ip/Versachem-15339-Dielectric-Connec... (mine is from Canadian Tire, at $13 or $14 a tube...)

It's chemically inert (even with Nitric acid) , has a nice, tacky, even surface contact, resists pretty impressive temperatures. So far, no complaints, I also have authentic Beckmans glassware joint grease, and I see no difference between the two.




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hissingnoise
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[*] posted on 13-3-2019 at 12:41


IMO, the one thing better than PTFE tape would be Glindemann Rings, also PTFE ─ has anyone here been able to get their hands on them?

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[*] posted on 13-3-2019 at 18:52


Quote: Originally posted by hissingnoise  
IMO, the one thing better than PTFE tape would be Glindemann Rings, also PTFE ─ has anyone here been able to get their hands on them?


I did not know what the details of Glindermann rings. But I found this web site see: http://www.glindemann.net. It says a groove is required in male part of the joint to hold the ring. Interestingly the groove looks smooth/polished not the frosted look of the lapped part of the joint and similar to the smooth/polished barrel of a PTFE stopcock.

The site claims its a high vacuum seal which is surprising to me if its sealing against a lapped surface and not a smooth one. Perhaps having such a small contact area relative to a sleeve, it has sufficient contact pressure to seal against the rough surface of barrel.

Although you have to buy a minimum of 200 the price per ring is less than 50p. That is much better than the typical cost of a sleeve at £10. But given a ring needs a groove, PTFE tape is the DIY solution. I doubt that the difference in thermal expansion between PTFE tape and borosilicate is a problem given how soft PTFE tape is.




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[*] posted on 14-3-2019 at 01:35


Quote: Originally posted by hissingnoise  
IMO, the one thing better than PTFE tape would be Glindemann Rings, also PTFE ─ has anyone here been able to get their hands on them?



I have something similar to these rings but it is an entire sleeve, but I only have one and it does work really well. I found some online for about $45 for 6 and some places were charging about $30 a piece. The sleeve is the length of the joint. If anyone lives in France, there is a chemistry supply company that sells these for a good price, about $15-20 for 6, but their international shipping was like $30 I think.

If anyone is interested, I can try to find the link to the site.

To everyone who replied, thanks for the info, I think I'll try the tape and see how it works.

On another note, I found on a few college chemistry guides and they recommend glycerin for things that don't involve reflux and aren't very high temp distillation.
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hissingnoise
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[*] posted on 14-3-2019 at 02:25


Quote:
I did not know what the details of Glindermann rings. But I found this web site see: http://www.glindemann.net. It says a groove is required in male part of the joint to hold the ring.

I hadn't heard of the groove before, so I assume it's not strictly necessary ─ earlier ads made no mention of them and suggested instead the use of 2 rings for vacuum work...

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[*] posted on 14-3-2019 at 04:30


Quote: Originally posted by Arthur Dent  
I use silicon dielectric compound, similar to this: https://www.walmart.com/ip/Versachem-15339-Dielectric-Connec... (mine is from Canadian Tire, at $13 or $14 a tube...)

It's chemically inert (even with Nitric acid) , has a nice, tacky, even surface contact, resists pretty impressive temperatures. So far, no complaints, I also have authentic Beckmans glassware joint grease, and I see no difference between the two.



Ooooh I have a Crappy tire near where I work, will check out, for me it will be perfect as I need Dielectric grease for my electrical stuff too! thanks.
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[*] posted on 14-3-2019 at 11:40


I use petrolium jelly to seal the joints when I use vacuum filtrations although it is not very chemically inert and melts if you heat it.



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[*] posted on 18-3-2019 at 07:14


Quote: Originally posted by RogueRose  


I have something similar to these rings but it is an entire sleeve, but I only have one and it does work really well. I found some online for about $45 for 6 and some places were charging about $30 a piece. The sleeve is the length of the joint. If anyone lives in France, there is a chemistry supply company that sells these for a good price, about $15-20 for 6, but their international shipping was like $30 I think.

If anyone is interested, I can try to find the link to the site.



It looks like everyone is carrying these in France.
It's even in the "public purchase" catalogue if you are an administration.
30 bucks is theft though (havent seen it). It should be the price for 10.

I think Scientific Equipment of Houston carries them in the US.
They also have fantastic PTFE keck clips. The last clips you'll ever need.
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