cloudy glass

[David Lyga]

Sometimes a lens is perfect EXCEPT one of the inner elements is cloudy (probably from past moisture which has turned into fungus). Oftentimes, fungus can be removed with careful wiping with either glass cleaner or lighter fluid. However, sometimes the cloudiness seems permanent and, thus, the entire optical use of the lens is destroyed.

Assuming one can get at that element by dismantling the lens (no, I am not talking about two cemented elements whereby the cement is the problem) is there any cure for that haze? Maybe someone has tried alternative liquids and come up with a solution. Thank you. - David Lyga

 

[ic-racer]

Some of the stuff that does clean off is oil. Even grease has some volatility and can condense on lens elements under the right conditions.

Grease is composed of molecules of varying molecular weight. With heat, the lighter molecules evaporate. This does two things, it allows the evaporated components the chance to re-deposit on a nearby surface (lens elements) and also causes the remaining grease to become thicker and stiffer.

 

[AgX]

I had haze on front lenses that I only succeeded in removing by using the strongest organic solvent I had on my shelves.

Optical glass used for outer lenses and their coatings seem very forgiving. concerning cleaning. At least that is my experience with lenses going back to the 50's.

But we got members with much more experience.


The only lens elements I would be utmost careful with would be those from Fluoride. But the appropriate lenses should be known to us.

In case of doubt of having a plastic lens in front of me I'm more careful than with glass lenses.

 

[02Pilot]

Depends on what it really is. Fungus will eventually etch glass - if that's the case, it's permanent. If it a substance on the surface, however, it can be removed. Glass cleaner and lighter fluid are fine for oil-based substances, but you may need something more specialized. Fungus is easily removed by moisturizing hand cream - apply generously, wait 5-10 minutes, remove and clean as normal. Haze that's formed as a result of off-gassing (usually from unstable lubricants) can sometimes be removed with toothpaste or silver polish; I've had better luck with the latter. Obviously, you need to be careful with the latter substances, as they are slightly abrasive.

 

[Tom1956]

Hello DL--hadn't seen you in a while. 2 days ago I finished up a Nippon Kogaku 50/1.4 that was full of fungus. In the end, the lens came out clean as a whistle, but when I turned it towards a lightbulb for the purpose of inducing flare, it was evident that the fungus had either etched the coatings and/or the glass. The lens was destroyed. Took it back apart for more agressive polishing with the toothpaste trick, but to no avail. It's a crying shame.

 

[Xmas]

When hard coating became available you could send your uncoated lens in to be coated.

To recoat they needed to dismantle, repeat the final polish and vacuum coat.

So it is possible to salvage an etched lens but you need a production style grinder and coating facility probably not economic for a Nikon lens.

 

[Nick Merritt]

There's been a lot written on this topic. Much depends on the age of the lens, and the brand -- Leica lenses of the 50s and early 60s are susceptible to this, and often there's nothing that can be done without damaging the coating of the surface that's affected. Leica interior coatings of this vintage are quite delicate. Sometimes it's in the glass itself, and can't be helped. Of course, given that they're Leica lenses, there is a lot more handwringing about the issue (you don't want to damage the lens, both from a monetary and picture taking standpoint).

I'm not sure other lens makes have this problem -- the Japanese lenses of that vintage seem to have had harder interior surface coatings. Also, newer lenses of all makes have improved coatings (and improved glass as well) so that the problem is not as severe.

Chances are the haze is on a lens surface that's adjacent to the aperture blades, so it's caused by offgassing from lubricants used for the aperture.

Hard though it may be to do, often the best thing to do is just resist the temptation to clean the surface, and instead get a proper lens hood to minimize flare. But if you do intend to clean an interior surface, I would suggest proper optical glass cleaner and as little pressure as possible applied with a clean, soft cloth. A lot of opinions on what sort of cloth, but microfiber seems to work well for me if it's clean. Likewise, a tissue is OK though it can leave lint. If it really looks like fungus, use hydrogen peroxide. I would not generally use lighter fluid to clean glass surfaces, however.

 

[Ian Grant]

Up until the late 1920s optical glasses were reasonably hard but then Schott (part owned by Zeiss) introduced new optical glasses that permitted new designs particularly for faster lenses. One used by Zeiss and Leitz was particularly soft and is prone to scratches and also atmospheric attack, Leitz used it for the Summar and it was also used in some Tessars and Novars. You can have what look like mint lenses, no cleaning marks or scratches, that are low contrast, sometimes unusable. Zeiss changed the glass in Tessars again towards the end of the 1930's when the first T coating was introduced.

Post WWII lenses varied considerably, the LF Zeiss lenses (CZJ) were much better so were the Zeiss (West Gernany) lenses, but some of the faster 35mm lenses still used softer glass not as soft as the preWWII glass but still prone to easily being scratched during careless cleaning.

What causes the atmospheric damage I'm not sure probably sulphur compounds from pollution but I acquired an EXA Ia recently with the legendary Meyer Domiplan and barely forms an image, through a loupe the surface of the front element looks like ground glass, yet the lens barrel and mount and rest of the elements all look mint. I have a second Domiplan with worn paintwork on the barrel but reasonable optics so need to get the lens cells swapped

With early coated lenses where fluorides were used in the coating fungus on a lens element absorbs the fluoride and weak Hydrofluoric acid can be formed etching into the glass surface.

Ian

 

[EdSawyer]

There are also haze issues when 2 cemented elements develop a haze in the join (within the adhesive). That requires separating and re-adhering them.

also, some glass can "precipitate" for lack of a better term. e.g. chemicals leach out of the glass to the surface and form an unremovable haze.

 

[AgX]

Precipitate... as you indicated that rather would be a kind of crystallisation I guess, rather than leaching out.

 

[snapguy]

Really?

What IG said is very interesting to me. I had a Summar on a Leica 3F and I thought it was akin to a Coke bottle bottom. Just awful. I wonder if that was the problem. The other lenses for that camera were fine including a Wollensak 127mm f 4.5 and an Elmar 90mm f4. I liked the latter lens, small and lightweight and very sharp.

 

[summicron1]

Sometimes a lens is perfect EXCEPT one of the inner elements is cloudy (probably from past moisture which has turned into fungus). Oftentimes, fungus can be removed with careful wiping with either glass cleaner or lighter fluid. However, sometimes the cloudiness seems permanent and, thus, the entire optical use of the lens is destroyed.

Assuming one can get at that element by dismantling the lens (no, I am not talking about two cemented elements whereby the cement is the problem) is there any cure for that haze? Maybe someone has tried alternative liquids and come up with a solution. Thank you. - David Lyga

not necessarily. I have an elmar 2.8M lens that i thought was "just hazy." Turned out it was oil/grease that had evaporated, condensed on the glass and then actually etched the glass surface. Total element replacement was the solution.

 

[chip j]

I bought a new 28mm 3.5 Nikkor in 1980 that had a noticeable cloud in it. It wasn't until I had printed some very nice pictures taken w/it that I noticed the cloud, though. Didn't seem to have much effect.

 

[dorff]

Just for interest's sake: There are proprietary fungus removal liquids, but the method my camera technician uses (and claims is better than the proprietary ones) is to cover the affected optic with shaving cream that contains menthol (eucalypt oil, I think). It is left to stand like that overnight, after which it is cleaned with water, and then alcohol. He has removed fungus from about 8 or so of my lenses (I bought them like that), and in all cases there is no etching visible after he is done with them. But I should add, these are all more recent Nikkors, and they probably don't have the soft glass issues of some of the earlier Leicas. He has also told me that very often the rear surface of the front element of a lens is soft-coated. This means a lens that has fungus on that element is to be approached with caution. Even wiping it with a normal lens cloth will leave damage. In a small number of cases, there are internal elements also with soft coatings, but they are very rare.

I am wondering whether the haze is in some cases the soft coating having been damaged by a cleaning attempt. That said, if it is that easy to damage, it must be that easy to entirely remove also, and if you can find a facility to coat it, it might be possible to give it a tougher coating. It may change the colour response of the lens, though.

I would never use a solvent on a cemented group, as it will cause separation if it gets in between the elements. Solvents are generally no use in getting fungus removed, but they may be the best way to remove grease.

 

[David Lyga]

Tom1956 (and others): the lens in question is an otherwise pristine Canon FL 1.4/50. I share my tears with you, Tom. And, yes, Tom and others, the 'light bulb' test is the absolute test to measure optical clarity.

Ed Sawyer: I had never heard of this 'precipitate': THAT causes such haze? I had thought that haze was primarily caused by moisture in the dark (i.e., fungus). The element does not seem to be 'etched' and I have had such problems with etching in the past. Obviously, then the actual physical surface would have been compromised. The problem currently is only a SURFACE haze (not separation of elements from cement failing).

And, yes, AgX, fluoride elements pose a particular problem. Thus, I warn ALL on APUG about the Minolta PF 1.4/58 formula: the second to last element (second from rear) is VERY fragile. I ruined one by lightly wiping in circular fashion after applying glass cleaner. I was rewarded with circular lines throughout the element. Still VERY sharp lens but the etchings amazed me.

The solutions proposed are very interesting and assuredly I will try ALL since the lens is now 'parts only' (with tears wiped away from my eyes). The temptation to make it pristine is very, very strong with me. - David Lyga

 

[Tom1956]

Many times after I have a lens disassembled a lens down to lone elements, I'll take them to the kitchen sink and wash them with my fingers and a little squirt of Ajax dishwashing liquid, which is slimy enough to keep the skin of my fingertips from abrading the coating, as the warm water is rinsing it away. Blot it with some CHEAP toilet paper, and finish with a fresh Q-tip. Use only genuine Q-tips, not store-brand, which causes greasy-looking swirls.

 

[Gerald C Koch]

Toothpaste is probably not a good choice for polishing lenses. Remember that it will scratch dentures that are not quite as hard as tooth enamel. A better choice would be cerium oxide. This can be used with fluorite elements. I have used it to polish optics used in IR spectroscopy which are made of sodium chloride. It can even be used with cesium bromide optics which are very soft. Check online with companies that sells supplies for telescope making.

 

[John Koehrer]

not necessarily. I have an elmar 2.8M lens that i thought was "just hazy." Turned out it was oil/grease that had evaporated, condensed on the glass and then actually etched the glass surface. Total element replacement was the solution.

Just did this too. The damage wasn't the total inner surface but was a shadow of the aperture stopped down to ~f8 with an undamaged center section.

 

[David Lyga]

02Pilot had a rather good idea with skin lotion. I just used some and, after 5 minutes I wiped it off with a clean, damp rag. There was a noticeable difference in clarity. Not all the cloudiness was gone but this was a better way to get rid of much of the cloudiness than other ways I had tried. I also tried jewelery cleaner and even bleach (!). Neither worked as well as the skin lotion. Multiple applications might be required and leave it on for at least a few minutes. - David Lyga