Cleaning the 100x objective

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Greg Howald
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Cleaning the 100x objective

#1 Post by Greg Howald » Wed Nov 30, 2022 2:40 am

I've had some difficulty getting the oil off the 100x objective lens. That piece of glass is very small indeed.
I'm open to suggestions.
Thanks

Dennis
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Re: Cleaning the 100x objective

#2 Post by Dennis » Wed Nov 30, 2022 4:58 am

Greg,
I am not speaking from experience just taking that as a challenge.
Soak end in 70% Isopropyl alcohol.
Then take a Zeiss lens wipe and fold it a few thicknesses and stick a tooth pick against it
Then take the wipe being between the toothpick and the OIL objective and feel around the circle with it.

Greg Howald
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Re: Cleaning the 100x objective

#3 Post by Greg Howald » Wed Nov 30, 2022 5:25 am

Thanks Dennis. I'll try that.

Dennis
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Re: Cleaning the 100x objective

#4 Post by Dennis » Wed Nov 30, 2022 5:28 am

Greg,
I figured a toothpick is semi soft wood where say a metal pick would not be a good choice in case it breaks through the wipe.

PeteM
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Re: Cleaning the 100x objective

#5 Post by PeteM » Wed Nov 30, 2022 9:52 am

Greg, One good thing is that 100% cleaning of the 100x objective may not be frequently needed. Proper immersion oil is highly resistant to oxidation, so simply blotting the lens to clear most of the oil (avoiding contaminating, say, the 40x objective) should be all that's needed in a session - maybe even in a couple days work. A fresh drop of oil can be added, blotted, added, blotted as needed throughout the day. Then, give it a thorough cleaning before letting it sit.

The design of the 100x objective also makes a difference in ease of cleaning. Ideally, there is a fairly large surface easily accessible to cleaning AND protection for the glass if the 100x is swung into position too low. Cheap 100x objectives sometimes seem to put a tiny lens deeply recessed into a cavity not much larger than a pinhole. These are, indeed, very hard to clean - especially if oil has oxidized and hardened. Better 100x objectives seem to have a larger front glass surface that's flush, and then a protective surround. These are much easier to clean.

For routine cleaning (not already-hardened oil), just getting enough of a mild solvent on the surface with a few gentle wipes should be enough. As others have said.

For I-can't-believe-they-left-the-lens-in-this-condition cleaning (hardened oil and debris), you may need a more aggressive solvent such as the hexane - IPA mix Zeiss recommends. I use tiny cone-shaped cotton swabs to reach into the periphery of the cheaper and sunk-in-tiny-holes objectives.

Many of the commercial lens cleaners include a bit of soap as well as solvent. I find these do a good job of removing fresh oil, without leaving oil streaks. Seems fewer swipes and whirls are needed to get the last bits of immersion oil. Someone with a better background in chemistry might explain oils, polar molecules, soaps, solvents, etc. involved in cleaning. But just from practical experience we know that cleaning something like oily fingerprints off eyeglasses works find with a bit of pure soap and clean water. With filthy eyepieces and other large optical surfaces, I may disassemble them and wash the individual lens elements in soap and pure water. Unlike wiping with a solvent, lots of water and soap lifts off grit and grime with less chance scratching the lens surfaces.

I'm a fan of microscopes with easily interchangeable lens turrets. Among other advantages, these make inspecting, handling, and cleaning objectives a bit easier than guessing what's going on or unscrewing and possibly dropping them. There's also the possibility of having one turret for dry-only use and another with long working distance low power dry objectives and something like 50x and 100x oil immersion objectives.

Greg Howald
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Re: Cleaning the 100x objective

#6 Post by Greg Howald » Wed Nov 30, 2022 9:18 pm

Thanks Pete. Appreciated.

tlansing
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Re: Cleaning the 100x objective

#7 Post by tlansing » Fri Dec 09, 2022 10:23 am

Hi Greg, just saw this post. A company that services microscopes told me that they use ROR Optical Lens Cleaner to remove oil from 100X objectives. I now use this and it works well.

PeteM
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Re: Cleaning the 100x objective

#8 Post by PeteM » Sat Dec 10, 2022 5:48 am

I use and like ROR (Residual Oil Remover) as well.

Here's the MSDS. It might be possible to mix up distilled water, something like Dawn soap, isopropyl alcohol, and dashes of ammonia and salt to get something similar?? Not sure what the NaCl in there does - perhaps help the IPA lift oil above the water level?? The tiny bit of ammonia may be a concern for some. I haven't noticed problems with it affecting coatings and things like eyepieces invariably get kids' finterprints on them after every session - so cleaning of those has been frequent.

Three handy small squeeze bottles of ROR (as sold on Amazon) last a long time, do the job, and aren't way too expensive.

"Sparkle" is another cleaner recommended by some. It contains 2-Butoxyethanol (a solvent also in some formulations of Windex), probably with lots of distilled water.

The Zeiss recommendation in "The Clean Microscope" is for 85% petroleum ether (light solvent, like Naptha) and 15% isopropanol (aka isopropyl alcohol). My impression with with cleaners that are all solvents, no soaps, is that it takes more swipes to lift off the last traces of fresh residual oil and fingerprints. Oxidized oils, stuck firmly to the lens, will want the solvents.
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ROR MSDS.png
ROR MSDS.png (81.8 KiB) Viewed 2488 times

viktor j nilsson
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Re: Cleaning the 100x objective

#9 Post by viktor j nilsson » Sat Dec 10, 2022 6:48 am

I agree with pretty much everything Pete says. When I have a really dirty lens, I tend to use ROR or Zeiss lens cleaner first. They clean oily stuff really well. But I find that they don't dry as cleanly and rapidly as pure solvents.

But for relatively clean lenses, and for finishing passes, I like using pure solvents. My favorites are petroleum ether (I use Zippo lighter fluid) and pure isopropyl alcohol. Haven't mixed them, though.

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