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  1. #1

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    Lens Separation - Crazy Idea?

    I have an old Gundlach triple convertible for 8x10 - it's a 12-21-28 rectigraph I believe - brass barrel. One of the lenses has the worst case of separation I've ever seen. The lens housing though is swaged over so the glass can't be easily removed although there was no problem unthreading the lens assembly from the barrel. What would happen if I just immersed the entire lens assembly in acetone for a day or two? Would it get in and disolve the balsam and would it them wash out? How bad would the lens performance be (given that the cell is entirely unusable anyway, except as a 28" lens, anything would be an improvement)?

    Thanks,
    Dan

  2. #2
    Ian Grant's Avatar
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    Steven Tribe on the Large Format Forum is the person to ask. He's fixed quite a few lenses and posted a thread on how to do it.

    Ian

  3. #3
    bsdunek's Avatar
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    Agree with Ian. Have somebody re-cement it. It's a shame to ruin a good old lens when it can be fixed.
    Bruce

    Moma don't take my Kodachrome away!
    Oops, Kodak just did!


    BruceCSdunekPhotography.zenfolio.com

  4. #4
    Ian Grant's Avatar
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    I have a Rodenstock early Sironar, pre the MC version, and that's separating, the company had problems with their first non balsam cements. There's lots of good advice on the other forum on getting elements apart etc, seems more people there tinker with these things.

    Steven Tribe is very helpful so ask before you do any damage

    Ian

  5. #5
    Steve Smith's Avatar
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    I don't know much about cementing lenses but would I be right to assume that they are optically linked by an optically clear material filling the space between the two lens surfaces?

    We use a UV cured optically clear adhesive at work. I was wondering if something like that could be used.


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  6. #6
    Ian Grant's Avatar
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    That's exactly what the manufacturers use, and also people doing repairs. For older lenses they also still use balsam.

    On the other forum a poster describes how to separate de-laminating modern elements, heat is used but he prefers not to use a furnace instead using hot/boiling water.

    I'll be looking for some UV cured Optical cement when I'm next in the UK

    Ian

  7. #7
    Steve Smith's Avatar
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    Quote Originally Posted by Ian Grant View Post
    I'll be looking for some UV cured Optical cement when I'm next in the UK
    Let me know when you are here and I will post some to you.


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  8. #8
    Ian Grant's Avatar
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    Quote Originally Posted by Steve Smith View Post
    Let me know when you are here and I will post some to you.
    Steve.
    Got to get the lens back first, but I'll take you up on that Steve

    It's been on a rather extended loan to an Italian APUG member, hopefully I'll we'll meet up in Venice next Saturday. I plan to put the lens elements in one or two of those bag things that come with washing powder tablets in the UK, that way I should be able to heat up the glass in hot water to separate the errant cell without them getting scratched.

    What's the optical cement you use called ?

    Ian

  9. #9
    desertrat's Avatar
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    One thing the OP mentioned was that the lens elements were "burnished" into the cell. All the suggestions on how to fix the problem are only useful if the elements can be removed from the cell. The only way to get them out is to carefully cut away the cell lip with a very thin, sharp cutting tool after chucking the cell into a lathe. I suppose the lip could also be cut away very carefully by hand with a dremel moto tool or similar small electric die grinder using a thin cut-off wheel. After this is done, some other means must be found to get the re-cemented elements to stay in the cell, because the lip isn't there anymore. A few small dabs of cement or torque paint might work.
    Happiness is a load of bulk chemicals, a handful of recipes, a brick of film and a box of paper. - desertrat

  10. #10
    Ian Grant's Avatar
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    One reason I suggested contacting Steven Tribe is I think he has some experience, and might be able to suggest the best option.

    I'll contact him myself before I attempt my own Sironar repair because any advice is invaluable in getting things right.

    Ian

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