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Author: Subject: Can I use any silicone grease from the hardware store as vacuum grease?
FireLion3
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[*] posted on 1-8-2017 at 04:20
Can I use any silicone grease from the hardware store as vacuum grease?


I can't see why it would be a problem. Usually I almost always see Dow Vacuum Grease being used for laboratory applications, but it's just Silicone Grease, isn't it?
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Heavy Walter
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[*] posted on 1-8-2017 at 05:54


Hi, thats depends on your specific application.
It is supposed the high vacuum grease avoids in its formulation products with high vapor pressure.
Just for sealing parts in a vacuum distillator common silicone grease will be fine.
For higher vacuum levels, involved in synthesis or fine chemistry, I would stick to Dow or any good brand.
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XeonTheMGPony
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[*] posted on 1-8-2017 at 06:12


I've used NFSA approved silicon greases for vacuums as low as 200milliTor with no issues
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FireLion3
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[*] posted on 1-8-2017 at 07:06


My vacuum pump pulls down to 0.075mmhg, and I do need all of that for the occasional high bp distillation. I have used plastic sleeves for my joints in the past, and they work fantastically, but I only have them for specific joint sizes, and not for smaller ones.


High Temp Silicone grease from the store is only like $3, whereas the cheapest Dow vacuum grease I can find is $20+. I have a vacuum gauge so I may just buy the cheap stuff and test out its efficacy and see what happens.
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XeonTheMGPony
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[*] posted on 1-8-2017 at 07:22


well I have had the greas as low as 20 millitorr with no issues, down to .1 it may but I doubt it and less you have a turbomolecular or a diffusion pump you wont be geting vacs of that level!
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Sulaiman
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[*] posted on 1-8-2017 at 08:02


I use a small tube of silicone grease aimed at the automotive market.
It seems to work well BUT it loses viscosity massively with increasing temperature,
a gel at RT, liquid in the palm of my hand, a thin oil during distillation.
It still works, but a higher melting temperature would be better - I guess.




CAUTION : Hobby Chemist, not Professional or even Amateur
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FireLion3
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[*] posted on 1-8-2017 at 11:00


I will probably still order some Dow Grease soon anyways. I should have noticed this online, but the hardware store grease was so cheap because the quantity in the tube was so small. Volume per volume, the Dow Grease is cheaper.


Quote: Originally posted by XeonTheMGPony  
well I have had the greas as low as 20 millitorr with no issues, down to .1 it may but I doubt it and less you have a turbomolecular or a diffusion pump you wont be geting vacs of that level!


The figure I mentioned in my previous post was mmhg. 0.075mmhg = 75 militorr, so I'm guessing I should be okay.

Quote: Originally posted by Sulaiman  
I use a small tube of silicone grease aimed at the automotive market.
It seems to work well BUT it loses viscosity massively with increasing temperature,
a gel at RT, liquid in the palm of my hand, a thin oil during distillation.
It still works, but a higher melting temperature would be better - I guess.


Hm that's odd, usually Silicone greases are used specifically for high temperature applications.

Fortunately for me though, the part I am greasing won't be having any heat contact. It's at the other end of the apparatus where the joint is an uncommon one. I try to use PTFE sleeves for the more standard joint sizes.
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subskune
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[*] posted on 1-8-2017 at 12:24


I use cheap glycerol most times vapour pressure is < 0,1 pa thats less than my 2 stage pump can pull



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[*] posted on 1-8-2017 at 18:48


I use dielectric grease from an automotive shop but a 50g tub of proper vacuum grease is pretty cheap on eBay, no real need to look for a substitute
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