separation repair

[laptoprob]

So I am planning on having my Steinheil Quinon Sonnar repaired. The rear element shows separation.
Will van Manen, one of the top dutch repairmen says the regluing is not the problem, but the separating is.
I remember having read a thread here about this but can't find it again: how can I speed up separation safely? Otherwise there is too much risk of breaking one of the lenses.

Was it gentle warmth? like 50C in my oven?

[laptoprob]

bump?bump?

[oftheherd]

I don't remember in what thread or what he recommended, but Brian Sweeny talked about that once, and how easily he had separated some lenses. You might try to contact him.

[clintock]

I think an optic that age will be glued with 'Canadian Balsam'. Xylene is the solvent for that, sold at stores that sell paint. I believe the large format guys encounter element separation more often than small format, maybe searchnig large format forums would turn up some more results.
The fear of cemented groups comes from the way some of them have a metal band around the group that can involve a machine to turn off.
Balsam is used to prepare microscope slides, so there may be someone at a school or lab around who could help find the solvent.
Also, balsam is (was?) used to attach the detector crystal to the face of the photomultiplier tube for physics experiments.
If you have the group out, i'd think putting it in a closed jar (with a cotton pad on the bottom to protect the glass) of xylene for a while should do the trick.

The modern way to glue them together is with some stuff that cures in UV light, supposedly lasts better than the balsam.

[laptoprob]

PM'd Brian, he is fast!
Suggested Isopropyl Alcohol as solvent. And google ofcourse. So I found out heating in water (to boiling, gently heating and cooling) softens the balsam.
Here is one of the more extensive reports: http://www.atmsite.org/contrib/Sapp/LensGlue/
I will leave the gluing bit to the pro I guess...

thanks all!

[Nikon Bob]

There was a thread the other day about cooking a lens element in an oven to cure a lens separation. I can't find it now but it may be another option for you.

Bob

[Wayno]

I've successfully used methylene chloride to seperate lens elements (both balsam and synthetic cements). It's a bit of a nasty chemical (read MSDS, take precautions), but it does a good job and doesn't harm coatings, etc. It can work overnight, but may take up to a week or more, depending on how bad the original seperation was to start with. It may be slow, but it's much less stressful than heating. I've found the Summers Optical UV curing cements very easy to use for re-cementing.

[Rob-F]

Seems to me that whether or not the re-cementing is a problem depends on the facilities available. Proper centering is a major issue in lens assembly. De-centering, even slightly, causes degraded performance. Will you have the means to center the elements to a very high tolerance?

[laptoprob]

The tolerance issue is the reason to have the recementing done by the pro.
I will try heating the elements soon.

[wolves3012]

Canada Balsam is soluble in Xylene. Methylene Chloride is a very aggresive chemical that doesn't really dissolve it - it lifts it by passing through the film and lubricating it. I'd certainly choose the Xylene route. Methylene Chloride is non-flammable, whereas Xylene isn't, but the former is seriously nasty stuff and the fumes from either can be quite narcotic!

[laptoprob]

So I got the rear element out. The glass is in a brass holder, tighthened with a circular clamp, a single piece of brass. I filed the last millimeter off to free the glass. Then I put the glass in water and heated for a few hours in the oven just below boiling temperature. This loosens the balsam which is just like a resin. This speeds up the separation, visible at the edges. The last bit can be loosened when the lens group is still warm.
Will van Manen, renowned Leica and lens tech has reglued it for me.
After puzzling the lens together and checking focus I will post a comparison of this Steinheil Quinon 50/2 lens to the Canon 50/1,5.