Strange Deterioration in old Zeiss Glass

[John R Smith]

Twice this year I have encountered old Hasselblad Zeiss ‘C’ lenses (silver ones, a 60mm and a 50mm) with serious problems in the glass. Has anyone else come across this?

The problem appears as a network or series of very fine, straight lines, which seem to have spread across a glass element. It looks a bit like a spider's web. They only show up when a strong light is shone against them from the rear, or when a light is shone across the glass at a very steep angle. Along with the lines there is also a cloudy, milky appearance. I have seen this twice now, as I say, and both times it has been in the middle of a front or rear group, not on the exposed element at front or rear of the cell which could be cleaned. As it is in the middle of a closed cell it is hard to understand how this has happened. Is this some sort of fungus, or if not, what is it?

Both times the lens has had to be retired from service.

John

[eronald]

Twice this year I have encountered old Hasselblad Zeiss ‘C’ lenses (silver ones, a 60mm and a 50mm) with serious problems in the glass. Has anyone else come across this?

The problem appears as a network or series of very fine, straight lines, which seem to have spread across a glass element. It looks a bit like a spider's web. They only show up when a strong light is shone against them from the rear, or when a light is shone across the glass at a very steep angle. Along with the lines there is also a cloudy, milky appearance. I have seen this twice now, as I say, and both times it has been in the middle of a front or rear group, not on the exposed element at front or rear of the cell which could be cleaned. As it is in the middle of a closed cell it is hard to understand how this has happened. Is this some sort of fungus, or if not, what is it?

Both times the lens has had to be retired from service.

John

Fungus in the cement between compound elements.

Edmund

[fredjeang]

Actually, could it be that a real spider made its nest inside the lenses? (because I have old Zeiss and an insect can perfectly enter the lens).

[John R Smith]

Fungus in the cement between compound elements.

Edmund

Yes, in the 60mm it could be, because that has one cemented pair. But the 50mm has seven elements and no cemented pairs, so there are no compound elements. And there is no room for a spider to get in there at all, Fred 

John

[fredjeang]

I was teasing you, trying to make your issue more funny.

[LiamStrain]

Definitely sounds like fungus to me. That does not require the cemented pairs...

It can be cleaned, and should... the fungus *can* cause permanent etching if not dealt with.


There can also be some cloudiness from evaporated lubricant, depositing on the lenses as well - but the rest of the description sounds like fungus.

Some tips from an old rangefinder forum thread here: http://www.rangefinderforum.com/forums/archive/index.php/t-2218.html

Universal advice, keep these lenses separate from your others - fungus can spread among lenses quickly.

[Fine_Art]

The horror of fungus on Zeiss.

Do you live in a humid climate? After getting it cleaned you could try a small cloth bag of rice in wherever you keep your lenses. It will soak up a lot of water from the air.

[theguywitha645d]

Fuji film sold fungicide packets in Japan you would keep with your equipment. Maybe they are also available where you are.

For now, place the lenses in a plastic bag with desiccant. The lack of humidity will at least impede if not stop the growth.

[fredjeang]

Got the definitive answer: http://matthewduclos.wordpress.com/2011/11/01/cleanlenses/

 

[neilwatson]

John,

I have a 250mm Super Achro lens C style which has a similar deterioration. 

One lens element has fine concentric rings all over it.   These are only visible if you shine an LED torch through the lens.   It really is quite slight and you have to look carefully to see.

I took the lens into a 3rd party Hasselblad service center many years ago and they told me they had seen one case like this before for the same type of lens.
They said it was a deterioration of the quartz element in the lens.   Actually a deterioration of the element itself.   Nothing to do with mold.   They said there was no point in opening up the lens for cleaning.

In my case the deterioration is not getting worse.  Its been the same for the 5 years I have had the lens.   
It seems to make no difference to image quality. 

In your case the lens do not have a quartz element in the design so not exactly the same thing.   

Just interested why did you have to retire the lens.   Did it make a difference to the image quality ?   Was the deterioration getting worse over time ?

Regards

Neil

[John R Smith]

Just interested why did you have to retire the lens.   Did it make a difference to the image quality ?   Was the deterioration getting worse over time ?

The lenses were retired for two reasons - as I suspected it was fungus I did not want to store or use the lenses with the rest of my kit, in case of cross-contamination. Secondly, I could find nobody prepared to dismantle the closed cells to clean the internal elements - even David Odess won't do that, so I have been told. These old Zeiss lenses (and many others, I would imagine) have a front and rear group, with the shutter in the middle. Each group comprises several elements in a closed cell, which looks like a real pig to dismantle. What I have done now is to find a couple of cheapie lenses which were really rough cosmetically but had clean glass, and I have swapped out the affected groups. It probably worked out less costly than a repair would have.

John

[neilwatson]

John,

That is a really good idea to swap the affected groups from one lens to another.   There are lots of the silver lens in bad condition being sold in the junk boxes at shops.  To buy two and swap the parts is a good idea.

Could you let me know what tools you use to dismantle the lens. ( I am wondering if I could get these tools on ebay )   
I have not done this before and want to give it a try on some junk lens and see how I get on.
I have a couple of lens that I would also like to try and clean as they have slight mold.   If the inside of lens is module it should be straight forward to dismantle and assemble again.

Regards

Neil

[John R Smith]

Could you let me know what tools you use to dismantle the lens. ( I am wondering if I could get these tools on ebay )   
I have not done this before and want to give it a try on some junk lens and see how I get on.
I have a couple of lens that I would also like to try and clean as they have slight mold.   If the inside of lens is module it should be straight forward to dismantle and assemble again.

Neil

The tool you need is what the Americans call a spanner wrench - I would call it a lens wrench. With this you can pop the front and rear groups out without damage to anything. Two provisos - on an old 'C' lens the cell threads can be very tight if nobody has had it apart in forty years or more. Get an assistant to hold the lens body firmly down on a bench while you apply the turning force. Do not let the wrench slip! When I re-assemble I put a tiny spot of copper grease on the threads. Secondly, when you do this the lens iris blades are of course exposed and you must be very careful not to accidentally damage them.


John

[neilwatson]

John,

Thanks,  have ordered a lens wrench.  Will start with a junk lens and see how it goes.

Been looking at some of the lens designs and seems that only certain elements are going to be accessible. 

What is best for cleaning mold/fungus off the glass elements? Is there a special fungus killer or just use lens cleaning fluid.

I suppose even if I am able to clean the lens the mold is going to come back as I would not be able to get it all out.

Bit of a danger this fungus stuff.

Regards

Neil

[John R Smith]

Neil

For cleaning old glass I have used alchohol (isopropanol). But don't use it on cemented pairs as it could dissolve the balsam. In theory, alchohol should sterilise the glass and kill off the bugs. However, fungus is known to be remarkably resilient. Another option I have tried is an aerosol fungicide sold by chemists to treat athlete's foot. Fungus is fungus, so I figured this might zap the lens variety too. Perhaps the only certain course of action would be to fumigate the lens in a closed cabinet with cyanide or whatever. This could be hazardous if you were a little bit casual in your approach . . .

As you say, some parts of lens groups and closed cells are not accessible in any case. But you can usually get at the back of the front element, as this is designed to be readily replaceable in case of impact damage.

John