Cleaning dried oil off a simple 4x objective

[zzffnn]

Happy new year! Thank you for checking my thread.

Please kindly advise me:

I have a short Nikon S 4x 0.1 objective that has some dried oil-like stuff on its top lens, which did not come off after being submerged in acetone, 75% or 90% alcohol, or WD40 for a day (soaking was done in that sequence).

Photos have been attached herein. Back lens' foggy view does not show up well in that photo (I don't have a proper macro rig for a better photo), but it is quite a bit worse.




I don't mind risking a total destruction at all (since buying another one only costs $20), but is there anything else that I should try?

I tried to access the top lens, but it has a cap like thingy that prevents complete access. Please see an example image of the objective here:

http://m.ebay.com/itm/Nikon-4x-0-1-Micr ... nav=SEARCH

That said, the dried oil-like stuff seems to be on the outside surface of top lens (not inside), so opening it up may not help much, unless I try to rub off the dired oil-like stuff. Probably not a good idea though, since chance of scratching is quite high if I rub its surface. But I don't mind destroying/scratching it, if this is the only way out.

Edit: The residue is slightly yellowish and glassy in appearance. Since I could not reach it or feel it, I can not be sure if it is greasy. Also it only shows up in oblique light under a loupe, otherwise when looking on a microscope, it is a slightly less transparent film that reduces clarity and contrast.

It does not look like Newton's ring. The residue is irregular in shape
and not rings, not optical reflection. What I have seems to be on the outer surface of top lens, though I could be wrong.

Couplets separation is not impossible. But mine is an achro 4x.

Your kind comment is highly appreciated. Thank you!

[zzffnn]

Photos have been added. Thank you for your help!

[Charles Krebs]

If (!) it really is a dried up oil on the outer surface you might want to try xylene or heptane (Bestine rubber cement thinner). Use appropriate personal safety techniques and caution when using these solvents! Some oils used for microscope immersion objectives and temporary mounting were not soluble in alcohol or acetone, but are with xylene and/or heptane.

Cedarwood oil was commonly used for oil immersion around the time this objective was made, and it could dry into a hard yellowish "solid" (although I don't know why or how a 4X would have immersion oil on it... but I suppose stranger things have happened). I don't know for sure what solvents works for that but I believe xylene is effective.

which did not come off after being submerged in acetone, 75% or 90% alcohol, or WD40 for a day

Really not a good idea. You should never immerse the front of an objective in a liquid, especially a solvent. (Obviously an oil-immersion objective used properly with microscope immersion oil is OK). Many of the optical cements, adhesives and seals used were easily destroyed or damaged this way. Incursion of these liquids into the objective almost guarantees you will have a new "paper-weight".

[Choronzon]

I'm guessing the front element has been etched by hydrofluoric acid fumes, I've seen this before, and front element replacement is the only fix; probably a total loss.

[zzffnn]

Thank you very much, gents.

This objective came from a Nikon model G upright scope, by the way. So the chance of that being dried oil is indeed low. Also I am guessing if there was oil on a upright objective, it should drip down and dried oil residue should be located in the center due to gravity (not like mine, whose pattern seems all over the place randomly).

HF acid fume makes sense and the etching pattern seems to be what we are seeing here.

Sorry, I was too rough in those soaking. That objective came to me for free and in a bad shape, so I thought that I had nothing to lose. But now, I suddently find myself needing a short barrel 4x and that one is the only one that I have with the correct working distance

[zzffnn]

I tried xylene + acetone today. It seemed to work. It is a product called "Goof Off" that can be bough from HomeDepot in US. I could not find a small size pure xylene at HomeDepot - what they have is a huge can that looks really hazardous - I have young kids so I did not buy that. Edit: HoneDepot also do not sell haptene, although I did see it being sold at Amazon.

That "grease" residue has been reduced to about 1/3 of its original size, after soaking (front lens surface only) in xylene + acetone for about 20 minutes.

The problem is, the objective's front lens is not fully accessible by Qtip - it has a narrow ring that allows only about 1/2 of the Qtip to get in (said ring is not removable - I did try). As a result, I could not sufficiently wipe the front lens clean. I wiped about 5 times with xylene + acetone, but did not see any further reduction of that "grease".

Is there a better way to clean that objective? Or just keep wiping again and again?

Thank you very much for your advice.

[RobertOToole]

Hi zzffnn

I have seen something called 'Goo Gone' gel (orange colored and scented) work miraculous wonders on tar, grease and oil etc. You can find it everywhere including dollar or 99 cent stores. Might be worth a try.

Best of luck and happy new year.

Robert

[Chris S.]

The problem is, the objective's front lens is not fully accessible by Qtip - it has a narrow ring that allows only about 1/2 of the Qtip to get in (said ring is not removable - I did try). As a result, I could not sufficiently wipe the front lens clean.

Fan, so either the tip of the Q-tip® is too large, or you need a similar product with a bendable shaft?

If so, maybe something like this (which I have no experience with): Baisadai® Disposable Micro Applicators. Listed features include (emphasis mine):

• Non-linting,
  Can be arbitrary bending angle,
  Disposable, clean and sanitary, prevent infection,
  Different sizes for different needs
  Use: Bonding agents, Smear, Etchants, Sealants,Remove eyelash extension.
  Small size: 1.0mm / Medium size: 2.0mm / Large size: 3.0mm.

Image source: Amazon.com listing linked to above.

If you try them, a report back would be appreciated!

--Chris

[Charles Krebs]

"Goof Off" is less than 10% xylene... mostly acetone. You determined earlier that acetone would not work, so whatever amount of xylene is in the product is likely what removed the deposit.

If you don't want to purchase a quart of 100% xylene you might want to try heptane which you can get as "Bestine Rubber Cement Solvent and Thinner" in a 4 ounce size:
http://tinyurl.com/zuf5cwl

(You should also be able to find it in most well stocked art supply stores).

You can try a wooden toothpick with the tip wrapped in a couple of layers of lens cleaning tissue to carefully get into small tight places.

[zzffnn]

Thank you very much, gents. You are very kind and konwledge! And best wishes for the new year!

I have cleaned the objective. Although I did a lousy job and took off some coating

It does not matter for my application though (which is scanning 1mm thick nanoaquarium slide in oblique light). I have compared the cleaned objective with a good Nikon E 4x/0.1 DIN version, using a stained slide and oblique light. Looking at tiny stained spikes/hairs/dots of a fixed water flea, I saw almost no difference.

I said, yesterday, that there was 1/3 of "residue" left on the top lens. That might be scratched-off coating actually (I did not check top lens carefully yesterday), so I likely over-treated the top lens. Not a surprise, with a first-timer and kids running around in the house (I cleaned the objective on a windy balcony, so no harm to kids). Today, I did clean further with a toothpick wrapped with lens paper - I felt that if there was any residue it would have worked well (though for the scratch, it did not seem to do anything more). But it is all good now.

That $3 Goof Off seems to be pretty strong stuff, it has a strong acetone smell and it melted one of my objective capsule (should have used glass container). I am glad $3 went that far and still have lots of left-over. I will probably use it next time, though I will use toothpick and be a lot more careful - probably avoiding soaking completely.

Thank you very much!!