One way to fix lens separation

[Bernard Kaye]

I am now boiling a Zeiss 50mm. f1.5 Sonnar (Contax) postwar, presumably UV glue, and ask who sells it and what is it called. It was a cull lens: I just finished "hand-machining" the mounting -camera attaching bayonet and hope to separate the rear and center assemblies (the front element is a single lens).
Please, what is the UV cement called and who sells it, presumably on line?
Thank you,
Bernie

[jack_hui]

They were originally bonded by modern UV glue (or epoxy?), and I believe that they are quite strong to dissolve by acetone.

One type of cement that I used is this
http://www.optical-cement.com/cement...l#anchor669157

[jp498]

Would index matching gel (as used in fiber optics) be suitable to interfacing two lens elements as well?

[Carnacki]

Jack,

Reviving this thread for a short post : I've just solved the separation problem on the rear group of my Sironar 135 thanks to you, although in a simplified way :

I unscrewed and took out the two outer (glued) elements of the rear group, where the separation occurred (unilateral, 3mm wide, amber)colored).The sides being black, I checked with solvent (turp) that it was just paint and not a fine metal casing - so far, so good. My strategy was to remove the paint , at least at the junction of the two elements, to allow melted balsam to seep out during heating, but I tried a first run in the boiling kettle just so, during 10 minutes.

Taking out the boiled element, I noticed the separation mark had changed shame, and somehow thinned out. I pressed the two sides together, and it seemed to me that the separation receded. So I put the elements to the boil, 10 minutes again and pressed the sides immediately on taking the element out.

It worked. I think luck allowed me to spread the melted balsam uniformly between the two components of the element. Well, at least, it does not show any irisation anymore.

I painted the sides back with black DVD marker (water- not solvent-based), let tie element dry, cleaned and put it back in the rear group mount with the retaining ring (the element was now completely cold, of course).

I am not sure this will last, but at least I know the first part of the modus operandi now, so I'll resort to re-glueing the two parts if need be, but I wish I could avoid this since the contact surface is plane, not curved, and the two parts don't have the same diameter, hence a possible centering nightmare...

But as I said, so far, so good. Thanks for the advice, I would never have dared boil lenses !!!

[E. von Hoegh]

Well ain't that slicker than snot on a doorknob!

I have an old Nikkor 35 f2 the needs some recementing.

[redu]

Jack, what black paint did you use on the sides after recementing..?

[John Kasaian]

Sally Mann just called and she's PO'ed!

[John Koehrer]

If the diameter of the two elements are the same, they can be aligned by gently clamping them between two "V" shaped pieces of material. I'm using 3/4" aluminum angle 3/4" tall and a small clamp.
It's gonna look something like this < O > where the arrows are the angled aluminum and O is the elements being aligned. Obviously the angles will be in contact with the sides of the elements.

[Carnacki]

If the diameter of the two elements are the same, they can be aligned by gently clamping them between two "V" shaped pieces of material. I'm using 3/4" aluminum angle 3/4" tall and a small clamp.
It's gonna look something like this < O > where the arrows are the angled aluminum and O is the elements being aligned. Obviously the angles will be in contact with the sides of the elements.

In case the elements are not of the same size (case of my Sironar), I would have used modeler's hard latex to make an imprint of the original assembly, then use it to hold the two unglued / reglued lenses It should work and, if you have taken the precaution of making an external enclosure of Lego or something of the kind (rigid) to contain the latex when making the imprint, it should be reasonably precise.

[jb7]

Well this is all very interesting-
particularly the idea that I might not need to completely dismantle the cells-

However, a problem- the two lenses that could benefit from this treatment have cells that are difficult to get at-

One is a Suter Aplanat, and the group seems to be crimped, or bonded, in.
Does anyone know how to remove it from the brass, or might it be possible to boil the complete assembly? If it were, that might actually be the favoured approach-

The other lens is more problematic, and might deserve a question in a dedicated thread...