What's this cr*p in helicoids?

ForenSeil · Joined: 15 Apr 2011 Posts: 2726 Location: Kiel, Germany.

I had some serious problems with an old Hexanon 57mm F1.4, focusing was very hard... mechanical cleaning with some alcohol and relubing didn't do the job, because the helicoids didn't get clean enough, even after 30min of cleaning.

So I decided to clean it the chemical way.
I first dumped the rings into boiling 90% ethanol. The ethanol turned yellow but it didn't dissolve the grey/black crap.
Than I tried a boling solution of 1:1 petrol ether + acetone... with good results. The solution turned turbid immediatly. The rings got clean fast.
After 3 threads and cooling down the solvent looked like this:

What's this stuff consisted of? Is this abrasion, dirt (skin cells etc.) or hardenet lubricant?
It's insolouble in petrol ether.

sichko · Joined: 20 Jun 2008 Posts: 2475 Location: South West UK

When you say that the solution turned turbid, did the black stuff actually dissolve or did it just form a suspension ?

Both graphite and molybdenum disulfide have layered strucures and they have been used in lubricants. But I don't think that either of them is actually soluble in the solvents you used.

Sevo · Expire: 2012-12-03

Could be graphite grease, or eroded aluminium.

ForenSeil · Joined: 15 Apr 2011 Posts: 2726 Location: Kiel, Germany.

Lloydy · Expire: 2022-01-01

Just a thought......

http://www.maplin.co.uk/ultra-7000-ultrasonic-cleaner-223108

would one of those cheap ultrasound cleaners do the trick for this kind of muck ?

ForenSeil · Joined: 15 Apr 2011 Posts: 2726 Location: Kiel, Germany.

Lloydy · Expire: 2022-01-01

I did think of getting one to try on fungused glass. But perhaps the money is better spent on good glass ?

Sevo · Expire: 2012-12-03

SXR_Mark · Joined: 12 Jun 2010 Posts: 506 Location: England

I have the ultra-sonic cleaner pictured and find it very effective and useful for general cleaning using just warm water with a bit of detergent added. But I would make the following points:

I would not use it to clean optical elements due to the risk of pitting of the surfaces (cavitation)
Never clean bearings or other close fitting components when assembled or they will be severely damaged by brinelling.
It will not shift heavy soiling and similar and therefore will not shift helicoid grease.

To remove old grease I would just wipe it off with a rag and my general purpose cleaning fluid (60% iso-propyl alcohol +40% tap water plus a few drops of detergent). After removing the bulk of the grease, a quick ultra sonic clean will finish the job off. Back when I used to work with ultra-high vacuum and everything had to be very well degreased, I used ultra-sonic cleaners and pure acetone. But even then, I mechanically cleaned the bulk of the grease off screw threads and the like with a nail brush and soap and water before the solvent cleaning. I don't see any need to go through a risky process of boiling flammable liquids.

To remove lens fungus I just wipe it off with a lens cloth and methanol. If you still see marks on the glass after this, then that is damage and will not come off with anything. I've tried other things to clean fungus (Pond's cold cream, ROR, dilute ammonia, acetone) and have never come across a lens that could be made cleaner than with just methanol. Basically, the fungus has either already damaged the lens (in which case there is nothing you can do) or it hasn't (in which case it will come off easily). That is my experience, but I've no doubt others will disagree vehemently.

Mark