Who can re-cement lens elements?

Discussion in 'Camera Building, Repairs & Modification' started by cooltouch, Jan 31, 2009.

  1. cooltouch

    cooltouch Member

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    I have an old Century Precision Optics 650mm f/6.8 preset telephoto lens that takes quite decent photos. Its front (and only?) "element" is a doublet that is beginning to separate around the edges. No fungus, just separation. It's easy enough to remove with a lens spanner, which I own.

    Is there a place in the US that I can send this optic to have it re-cemented? I've found a few how-to links online, but I don't know if I have the proper tools for the recementing procedure.

    Thanks,

    Michael
     
  2. Phil

    Phil Member

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  3. Richard Wasserman

    Richard Wasserman Member

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    I too would recommend Focal Point. I have had work done by John VanStelton and he is among the very best.

    Richard Wasserman
     
  4. cooltouch

    cooltouch Member

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    Thanks guys. Email sent.

    Best,

    Michael
     
  5. Greg_E

    Greg_E Member

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    I see they also provide anti reflective coating work too, I'll have to book mark them for future work.
     
  6. Anscojohn

    Anscojohn Subscriber

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    *******
    Since a lens of that vintage is probably cemented with canada balsam, there is a way to heat the lens, very gradually, in a normal oven; allow it to reach the proper temp (I think it was 350F hold for a time; then gradually reduce to room temp. I did this once with an enlarging anastigmat.
     
  7. Kino

    Kino Member

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    I have a pair of Mitchell Baltar primes I sold to a man in China that were returned with separation in the exact same element on each lens. The separation was not there when it left and I have a strong suspicion it was induced by the buyer, who seemed to have buyer's remorse upon winning BOTH lenses in separate auctions! :mad:

    In any event, one of the lenses mounts has a big ding in it, but Paypal refused to accept the auction pictures as before and the returned lens pix as evidence. Said I could have manipulated them, so therefore, I couldn't be trusted...

    Now, 3 months later, I am out $700 USD (they issued a payback refund despite my tons of evidence and objections)AND and a pair of Baltar Primes!

    What makes me crazy is the lenses were returned with very well defined and heavy separation that looks suspiciously like someone dipped their finger in a mild solvent and ran it around the elements (middle doublet that is VERY easy to remove).

    I cannot believe the temperature variations between here and China during air mail caused the separations.

    Regardless, I will never use paypal or Ebay again!

    I might try that heating in the oven trick and see if it works; I have little more to loose...
     
  8. cooltouch

    cooltouch Member

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    So I take it then that if I follow this procedure, the two elements should separate easily? What about re-cementing them? I've bookmarked Summers, so I'll have a source for the cement, at least, but I don't know what sort of clamping procedures, if any, should be used. I do a lot of precision woodworking, so I have clamps out the wazoo, but none of them work very well on curved surfaces. I suppose a padded vise might work. I don't know the interior curvature of this doublet. If it's convex, then the vise will apply pressure at only two points. If it's flat, or even concave, then it will apply even pressure against the back surface, but only at one point at the front element. Is this advisable?

    Best,

    Michael
     
    Last edited by a moderator: Feb 1, 2009
  9. John Koehrer

    John Koehrer Subscriber

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    cooltouch,
    I just use acetone as a solvent for the Balsam. Let the elements sit in the acetone for a few hours or overnight & they come right apart. Any glue remaining on the glued surfaces can easily be removed with a Q-tip & Acetone. Alignment is critical when reassembling Use a pair of "V" clamps "<O>" wood with a notch in the ends works to hold the glass while the glue sets.
    I use "Crystal Clear" which is available at Ace hardware, it's around $5 for a lifetime supply. When using it the surface to be glued have to be clean. ONE drop in the center of the concave lens is all it takes. Apply the drop, make sure there are NO bubbles, & gently set the convex lens on the drop of glue. Use the lens to spread the glue evenly by rotating & sliding the two lenses together. The cement will actually hold the glasses together, all you need is the clamping action from the sides. If they're not in alignment, they won't fit back into the barrel. You will need to clean the excess cement from the edges of the elements before they've set. I just use a glossy black spray from the hobby shop to blacken the edges. VERY light coats.
     
  10. cooltouch

    cooltouch Member

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    Thanks for the reply, John. This may be easier than I thought. I take it by "V" clamps, you mean something like this?

    [​IMG]

    Those should be easy enough to cobble together from some hardwood scrap I have laying around.

    Best,

    Michael
     
  11. Greg_E

    Greg_E Member

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    I think I might line the V with some felt or something to keep from scratching the lens elements, but it's just a guess since I've never done this type of repair.


    Some UV cure glue would be great for this, all you would need to to is take it out in the sunshine to cure it.
     
  12. Bob-D659

    Bob-D659 Member

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    UV cure cement would be better, or you could just use Canada Balsam again. CB is a slow cure cement, UV cure is A. fast, and B, PERMANENT. Ie, mess up the alignment and it will stay that way. Also, look for scribe marks on the edges of the element before you solvent soak them. It's not uncommon for them to be there to mark proper alignment of the doublet before it is cemented. If there aren't any, mark the edges so you can put them back in alignment. Also check if the two lenses are in cylindrical alignment. They might have been cemented off axis to make them align optically, or maybe they were ground to form a cylinder after being cemented which may have removed the scribe marks.
     
  13. Phil

    Phil Member

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  14. cooltouch

    cooltouch Member

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    Sunshine I usually have plenty of, even in the winter, down here in Houston. Watch, though, when I finally try to do this, we'll have a week's worth of rain. :rolleyes: But then I remind myself that UV rays pass through clouds. I'll be more concerned about temperature, though. Most glues I work with don't like it when temps fall below 50F.

    Not to worry about scratches. The wood should contact only the edges of the elements, and besides, glass is a lot harder than wood anyway. I've got a lot of Spanish cedar scrap -- it's a hardwood, technically, but almost as soft as pine. Should work okay, I'm thinking.

    Bob, thanks for the scribe mark tips. I'll be sure to look for any. Interesting -- I ran across an optic once that appeared to have been cemented off-axis. Now I know why!

    Best,

    Michael
     
  15. John Koehrer

    John Koehrer Subscriber

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    Michael,
    That's exactly what I meant by "V" clamps. They don't have to be anything fancy, ply or pine works fine. It just has to be thick enough to keep both pieces aligned not to apply pressure of more than a couple of ounces. I just us small clamps with the squeeze trigger.
    I should have mentioned that when I have the elements together I do apply pressure with my fingers initially for a firm bond.
    Make sure there's no residue from the cement on the surfaces of the glass. If you use the UV stuff it's imf**king possible to get off.
     
  16. cooltouch

    cooltouch Member

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    I received an email today from John Van Stelten over at Focal Point. Cost to re-cement my doublet will be somewhere in the neighborhood between $195-250. I'm sure they do top-notch work, but that's quite a bit more than I paid for the lens, so I reckon I'll give it a go myself.

    BTW, I was reviewing the instructions over at Summers for their various UV cements, and they recommend the use of a 365nm wavelength black light for best results. I'm wondering if regular old sunlight might suffice? It's bound to have a 365nm component.

    Best,

    Michael
     
  17. cowanw

    cowanw Member

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    You might try Camtech Photographic Services
    http://www.camtechphoto.com/
    They will do a great job at much less than your other quote ( not to mention your dollar will go a long way up here again)
    They did my first Wolensak lens that was totally separated and it is fantastic. Give them an email. Can't hurt
     
  18. John Koehrer

    John Koehrer Subscriber

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    Sunlight works just fine.
    Sometimes the engineers at Summers and just too specific. For fine, highly critical work you may need that kind of specificity. 90% of the time ,,,,NOT! Kinda like the argument that you need a collimator to reassemble or focus a lens.
    The standards to which equipment is made both recently and not so recently make alignment errors pretty negligible. Unless you're the guy that uses test charts and microscopes.
     
  19. Windscale

    Windscale Member

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    Last edited by a moderator: Feb 10, 2009
  20. Ralph Javins

    Ralph Javins Member

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    Good morning, Windscale;

    A quick request for a confirmation of an old memory:

    Isn't Croydon on the A-26 south "of" London? Or has London grown that far south now?
     
  21. Windscale

    Windscale Member

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    Croydon is in Surrey. But London has stretched out so much in the past few years that many would regard Croydon as south London as one can get there by using a London Transport all zone ticket by train.
     
  22. Bob-D659

    Bob-D659 Member

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    The dividing line between London and Croydon was hard to find 40 years ago when I lived there. :smile:
     
  23. kenb

    kenb Member

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    shipped lens separation

    I THINK IT HAPPENS WHEN SHIPPED BY AIR IN AN UNPRESSURIZED, UNHEATED COMPARTMENT, SO I ADDED THE FOLLOWING TO THE START OF "MY POLICIES" IN BLACKTHORN AND CURRENT LISTINGS.

    LENSES SHIPPED OVERSEAS HAVE SUFFERED SEPARATION OF THE CEMENTED ELEMENTS, ESPECIALLY OLDER LENSES. I SUSPECT IT HAPPENS WHEN SHIPPED BY AIR IN AN UNPRESSURIZED AND/OR UNHEATED COMPARTMENT. THEREFORE, IF YOU BID ON A LENS TO BE SHIPPED OFF THE US CONTINENT, YOU MUST AGREE, BY EMAIL, THAT YOU ACCEPT THE RESPONSIBILITY FOR THE DAMAGE, WILL NOT MAKE ANY CLAIM OR COMPLAINT ABOUT SUCH DAMAGE, AND WILL NOT MAKE NEGATIVE OR NEUTRAL FEEDBACK. WE WILL HELP YOU FILE A CLAIM THROUGH THE US POST OFFICE AND SEND YOU ANY RECOVERED MONEY VIA PAYPAL.
     
  24. Mustafa Umut Sarac

    Mustafa Umut Sarac Member

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    I dont think do it yourself seperation procedure is a good idea. There is a big Leica forum at the web and there is a woman repair person who is trusted with most Leica owners. She said different glasses and their expansion rate in the heat tend to break the lenses. I am not remembering now , did I read here or there but there is special chemical baths which do the seperation without heat.
    Recementing is expert business and I dont think you can do it well without a optical setup for this purpose.
    Your lens is seem to worthy to pay for repair.

    Umut
     
  25. suzyj

    suzyj Member

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    Just checking the forum title... This is the camera repair forum, isn't it? Not the "you're not clever enough to do it, so you should send it to an expert" forum...

    I successfully separated an eyepiece doublet recently, and after a few false starts successfully re-cemented it using Canada balsam.

    The procedure isn't particularly difficult. Sure, some patience is required, and you might need adult supervision as you'll be using acetone and xylene, but otherwise it's not so hard, and can be done in most any kitchen.