A permanent grease for sealed microscope components: Krytox

[mneium]

I've been reading up about microscope repair and one of the demons of the industry seems to be solidified grease. My mind came to a grease I'm familiar with from building keyboards (it is often used to grease switches in custom mechanical keyboards): Krytox. This stuff is not silicone grease, it's pure PTFE. The lubricant itself is PTFE, and to make the grease it's thickened with... more PTFE. Don't ask me how that works. Since PTFE doesn't go bad, there is apparently no service life for it: "Grease samples from 20-year-old bearings have been examined and the grease was found to be in good condition."

The cost is steep, a 2oz tube is $40. It is however really, really nice grease that essentially futureproofs the moving parts of your microscope. It's also one of those cases where a little goes a long way. Just the slightest application with a paintbrush has my BH-2 head's IPD adjusting like butter, and it feels nice to know it will probably remain that way even after I'm pushing up daisies.

I can recommend GPL 204, 205, 206 or 207 for microscopes. They go in ascending order of viscosity. The line goes all the way down to 201, which is rather thin. There are also oils that are compositionally similar to the grease but un-thickened: GPL 101-107.

I wouldn't use this stuff on exposed stage bearings because it's just too expensive to replace often, but for everything else that needs to slide nicely and do it for a long time, there is AFAIK nothing better.

[MichaelG.]

Very impressive performance !!
Thanks for the link to the note.

MichaelG.

[Rorschach]

Thanks for this, highly interesting!

I have a few different Nye synthetic lubricant products for my scopes. They seem to be well regarded but I have no long term experience yet.

[mneium]

I have a few different Nye synthetic lubricant products for my scopes. They seem to be well regarded but I have no long term experience yet.

Nyogel - I have used it for many years. Another expensive lubricant. It is popular for flashlight threads.
It eventually seems to cloud up and become not as slippery, but I'm sure it would long outlast your average silicone stuff from a hardware store.

[abednego1995]

Excellent stuff! I just got a 2oz tube of 206, and
it works wonders. I've went as far as relubing most of my objectives with correction collars, no sticking again! (hopefully)

BR,
John

[mneium]

Excellent stuff! I just got a 2oz tube of 206, and
it works wonders. I've went as far as relubing most of my objectives with correction collars, no sticking again! (hopefully)

BR,
John

206 is great - IIRC it is the most popular choice in keyboards. The heavy greases are versatile. You can always dilute them with more oil (minor correction to the OP - it is apparently PFPE oil, not PTFE) to reach lower grades of viscosity, but you can't practically add more thickener to reach higher ones.

[mnmyco]

Pure PTFE is a solid until ~327 C and is practically insoluble in everything. Anything claiming to be pure PTFE and is not a solid is not pure PFTE and has a carrier in it.

[mneium]

Pure PTFE is a solid until ~327 C and is practically insoluble in everything. Anything claiming to be pure PTFE and is not a solid is not pure PFTE and has a carrier in it.

Yeah, the oil is PFPE and it's thickened with PTFE, my bad.


In doing some research on PFPE oils today I found something interesting. Dupont makes two basic formulations of PFPE oil - one is GPL (general purpose lubricant) and the other is VPF (vacuum pump fluid). VPF is about 2x-3x cheaper than GPL. I initially thought it was a lower-grade product, but four-bearing tests reflect that it actually has slightly superior lubrication & bearing wear results compared to GPL. The chief difference seems to be temperature resistance. GPL sustains high temperatures (greater than 200C) better than VPF. Not a big deal for our purposes. VPF also is specifically formulated to avoid evaporation since that's a big problem in vacuum pumps. And that should mean if you apply it inside a microscope, it'll stay there longer.

To give a "TL;DR": if you're buying a flourinated oil for microscope maintenance, go with VPF instead of GPL because it's both cheaper and better. You could also purchase ultrafine PTFE powder and make your own grease with VPF oil. Should work out to a relatively cheap version of this rather expensive grease.

[mneium]

Bumping this thread to add an additional lubrication trick I've found.

You know how microscope stage rails & bearings tend to collect gunk if you lube them (which compels some people to leave them un-lubed?)
You can prepare a very effective dry lube, which repels gunk but keeps nice lubricity, by mixing the following:

10 parts wax (microcrystalline is best, beeswax and paraffin both acceptable. You can even use candle wax, which is usually mostly paraffin)
0.1 - 1 parts micro-fine PTFE powder

1) Clean the rails & bearings very thoroughly (I use an ultrasonic jewelry cleaner filled with isopropanol. You can pick them up for $15 used on eBay.)
2) Use a double-boiler (ie. put an empty pot inside another pot filled with water, as if you were melting chocolate) to melt the wax. Mix in the PTFE.
3) Put a strainer into the hot wax-PTFE mixture. Immerse the bearings and rails. After all air bubbles have escaped from rails, remove.
4) Let sit overnight, then reassemble

If you're using paraffin wax, you can also add a small quantity of paraffin oil (eg. lamp oil) to increase lubricity and tackyness.
If this process seems familiar to you, it's because it's exactly what professional cyclists do to their bicycle chains, since wet lubes attract gunk.

[abednego1995]

Nice addition. Where do you get that fine PTFE powder?

Cheers,
John

[mneium]

Nice addition. Where do you get that fine PTFE powder?

Cheers,
John

You can buy it from Chinese retailers but it's very overpriced there. They do not offer submicron sizes of powder either.
I bought a 1kg sample of submicron PTFE powder from Shamrock Technologies, a US fluoroplastics company, which ran me $25. Of course, 1kg is far excessive for microscopy, but I use it for other stuff too. Great stuff for putting into locks, putting on bike chains, etc.

[MicroBob]

Hi together,
in my experience there is no real problem with the classic instrument lubricants, they usually last for decades and there is no dirt accumulation that really has an impact on usability. What often is important in these lubricants it to provide a smooth and well dampened movement. For this the greases are optimised and do their job well. I don't think that in this applications a lubricant with particles really is an improvement. Especially in sliding guides there is very little gap for the lubricant layer and the typical instrument greases work just fine.
Where I see an andvantage for lubricants containing PTFE is in guides that are fitted not very well, but thes are not to be found in good microscopes.

Bob

[mneium]

in my experience there is no real problem with the classic instrument lubricants, they usually last for decades and there is no dirt accumulation that really has an impact on usability.

I can't say I've ever heard of petroleum greases lasting decades, even the expensive ones like nyogel. How many times have you bought microscope parts and found that they're either seized or near-seized coz of old grease? That can't happen with PFPE/PTFE ever, which for me is a comfort.

[quantum]

I am a newcomer to machine greases, for disclosure, but one thing I am wondering about is whether the PFPE oil component would creep, or not.

[mneium]

I am a newcomer to machine greases, for disclosure, but one thing I am wondering about is whether the PFPE oil component would creep, or not.

I personally have never observed any separation of the oil in 5+ years of using PFPE-PTFE greases for just about everything I lubricate. As for whether pure PFPE oil creeps, I'm not sure how to test this, but I don't really think so. It isn't like a penetrating oil