Albada viewfinder restoration

Bruce Butterfield

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I have a very nice post-war Super Ikonta 521 6x4.5 that is fun to use with the exception of the viewfinder which is quite dark and difficult to use in lower light situations. It seems to be a problem with the front silvered mask element rather than the rear lens. Can I assume that the mask is not recoverable and I should hunt for a parts camera to replace it or is there some magic to "clean" the mask (I doubt that but I'm pretty ignorant of appropriate recovery techniques.) Or alternatively can I desilver the mask and just use it as a standard reverse Galilean without frame lines?
 

Dan Daniel

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Soak the silvered glass in acetone. It will remove the tarnished silver. In my experience, the viewfinder on the 6x4.5 Zeiss cameras is so sloppy to begin with that within a roll or two you will adapt to the lack of the framing lines in the viewfinder (i.e. full viewfinder is pretty well equal to full frame negative).
 
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Bruce Butterfield

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Thanks, I’ll give that a try. I don’t do a ton of critical framing with this style of camera anyway.
 
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Bruce Butterfield

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The front lens consists of two glass elements glued together (see photo) — if the acetone dissolves the glue as well as the silver what is the best way to glue them back together?
 

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Dan Daniel

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Will the silvering come with wiping with acetone? I know that I got it off fairly easily and that I didn't need to reglue the pair, but don't remember the actual steps. But yeah, it doesn't look like a good idea to soak the whole thing.
 

Mr Flibble

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Bruce Butterfield said:
The front lens consists of two glass elements glued together (see photo) — if the acetone dissolves the glue as well as the silver what is the best way to glue them back together?
Click to expand...

I've used Norland UV-curing optical adhesive for this exact same job.

Unfortunately I've not found an affordable way to repair the half-mirror coating itself
 
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Bruce Butterfield

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Mr Flibble said:
I've used Norland UV-curing optical adhesive for this exact same job.

Unfortunately I've not found an affordable way to repair the half-mirror coating itself
Click to expand...

Fortunately I don’t need to replace the coating; I just want to remove it and glue the elements back together. Do you know of any alternatives to the Norland products — it isn’t worth buying something that expensive for a one-time repair.
 

reddesert

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Canada balsam isn't cheap either. Generally, people's complaint about half-silvering is its fragility, so if you want to get rid of it I would start by wiping with a cloth and gentler solvents (water, alcohol, etc). It might just come off. If you have to use acetone, wiping the outer surface and not getting it on the seam will probably not affect the optical cement or balsam.

For silver objects there is a way to electrochemically reconvert silver sulfide tarnish to silver with a solution of (IIRC) baking soda in water and placing the item in contact with aluminum foil - the sulfur ions migrate to the aluminum. I doubt that this would work magic on a tarnished half silvered surface, but if you've already given up on the brightlines, could be worth an experiment.
 
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Bruce Butterfield

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I had to separate the lens since the silver layer I wanted to remove was deposited on an internal face of the elements. Those elements are now separated so now I need to gently scrub off the silver and re-glue. So far so good!
 

reddesert

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Over on the large format forum (the largeformatphotography.info forum, not the subforum here), someone described re-adhering two lens elements with a small drop of oil. Something like that might be worth trying without the commitment of optical cement or finding balsam.
 
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Bruce Butterfield

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I think I found the post you’re referring to:

Any tips on how to repair lenses with Balsam Separation? - Page 3

Hi all, So I bought two lenses suffering from Balsam Separation on the cheap that I would like to try and fix. Since they were bought cheaply, I’m not worried if I totally destroy them. The inner-rear elements that had been cemented together with Balsam that has since separated and has...
www.largeformatphotography.info

Not sure that canola oil will work in this situation since the lens is mounted in a simple frame that only attaches to the rear element of the lens. Thanks for the info in any case.
 

Dan Daniel

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On Ebay you can buy very small quantities of UV optical adhesive. Even a kit that includes a UV flashlight. I may have actually used one when I did a finder like this? I don't remember.

And at Lowes there is a Loctite Glass Adhesive. I've used it successfully for smaller areas; it might work here. Acetone will dissolve it if it goes wrong (I think it is based on a super glue of some form).
 
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Bruce Butterfield

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I’ve ordered a UV optical adhesive kit from Amazon, should be here tomorrow. Seems like the major advantage of the UV over the super glue adhesives is that you have time to properly center the elements before the adhesive sets. In any case this is more of an experiment than anything else and I’ve already learned enough to make it worthwhile.
 

eli griggs

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Mr Flibble said:
I've used Norland UV-curing optical adhesive for this exact same job.

Unfortunately I've not found an affordable way to repair the half-mirror coating itself
Click to expand...

Can not a small, electrical plating rig be jury-rigged, be made and then the new surface of .9999 silver be polished up by hand?
 

Dan Daniel

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Even in the best of condition, this type of viewfinder is a bit of a kludge. So a great thing to learn with.

I'll be curious to hear how you get on with the UV adhesive. One thing that I don't remember is how I got rid of material that comes out of the joint area.
 
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Bruce Butterfield

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eli griggs said:
Can not a small, electrical plating rig be jury-rigged, be made and then the new surface of .9999 silver be polished up by hand?
Click to expand...

I’m way too lazy for that as well as being mechanically incompetent. Plus frankly as Dan has said it just isn’t worth the effort.
 

reddesert

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Typically, electroplating deposits the plated metal onto a conductive surface. So plating metal onto metal, for example. Plating metal onto a non-conductive surface like glass would require depositing a conductive layer onto the glass first. This is non-trivial. Coating mirrors seems to commonly involve chemical and/or deposition processes, probably more often than electroplating. Astronomical mirrors are typically coated by evaporating metal onto the mirror under vacuum. See https://en.wikipedia.org/wiki/Silvering

If someone had a means to easily recoat fully reflective surfaces, it would be in demand for recoating such things as SLR prisms with degraded coatings, but I have not heard of any inexpensive way of doing that.

I imagine that controlling the deposition or plating process to deposit just enough silver or aluminum to make a half silvered surface as in a brightline finder or RF prism is even more challenging. This isn't really home-mechanic stuff, unfortunately.
 

eli griggs

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I was thinking there is mostly old silver coating is already distributed over the mirror area and would act as the conductor, with .9999 silver being applied not only being polished but, being soft, filling micro putting, where the old surface has failed.

Also, it might be a high quality duel conductive copper adhesive tape applied would serve as the base metal for coating with .9999 silver and polished up as a new mirror surface.

As far as being tech heavy, it's not, and a two each, C type 3v flashlight rifle bore electrolysis cleaner, might be a good demo device to fool around with, some appropriate silver, a waxed paper cup and ammonia in water (or other electroplating/electrolysis fluid) as a starting point to play with.

Higher voltages can also be employed but for such a small job and because it does involve electricity, 3-6v C or D cells would be the limit I would be willing to try, being electrically stupid.

How many layers should a first surface mirror require?
 
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Bruce Butterfield

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Cemented and installed. The inexpensive UV resin seems to be fine but time will tell. Very easy to apply, I cleaned off the excess with lighter fluid and Kimwipes.
 

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bernard_L

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Silvering the inside of a test tube by having sugar react with silver nitrate, as illustrated in the Wikipedia article, is as far as I remember, a senior high school or freshman level chemistry experiment. Maybe adhesion is not ideal...
Yes, definitely. That is where lies the challenge. Maybe need to slow down the silver nitrate - sugar reaction enough that it can be stopped by inspection?
 
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