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  1. #21

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    Thanks to a link that one of you posted (repeated here http://www.optical-cement.com/cements/decementing/decementing.html
    this was for a product made for the purpose. This product is to be used at 340 degrees F. All of a sudden, 212 degrees pales in comparison on the possibility of lens fracture. I had my buddy stop by after work and I explained my options. I have the go-ahead to try the water boiling. If it does not work, our agreed logic is that it might work well enough to go back to the solvent method with better effectiveness. Because right now, 2 days in Acetone has done nothing. Being the stubborn man, he refuses to believe that it could take a whole month in MEK. Hell, I can't get him to believe in the principle of the double-boiler. He refuses to believe that an ordinary metal cookpot can be brought to a boil in a bigger cookpot of boiling water. Of course it can.

  2. #22

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    Well, boiling didn't work. Didn't even faze it. Next up--methylene chloride. Will be several days before I can get my hands on some. Can buy MEK tomorrow, but am too cheap.

  3. #23

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    The more interesting question might be how you plan on re-centering the elements.

  4. #24

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    The same way they are now. They're totally flush all the way around. If they're off by a molecule I'm not going to sweat it. My buddy will be happy. It's no-good now, isn't it? If you want a perfect one go on fleabay and pay 4 or 5 hundred dollars for one. Or send it off to somebody and pay the worth of it to have it done on their fancy microscopes. My approach is free, I'm not a boob, and I do careful work, and I won't scratch it. So...

  5. #25

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    MEK/Acetone won't work. Xylene, maybe, never tried it.
    Methylene Chloride will do the job. It's the only solvent that has separated UV cure cement for me.
    After a week in MEK it took less than two days in the Methylene chloride. It's the main component in some paint strippers. I use is Parks Pro Stripper. 32 oz is a common size from the hardware store. Brand won't make a difference but it HAS to have the MC as the Primary component.

    If you want, send it to me & I'll separate it for you. 32oz is about two lifetime supplies.

    RE: recentering. I use two pieces of 3/4" aluminum angle. Set the glass in place and one angle on each side. Hold 'em together with a rubber band or two.
    It's gonna look like this <O>. I use a UV cure cement and wipe the edges with a paper towel dampened with Acetone. The edges are painted with a glossy black enamel. As long as it's OK for glass, it works on the lens group.
    Last edited by John Koehrer; 07-26-2013 at 06:53 PM. Click to view previous post history.
    Heavily sedated for your protection.

  6. #26
    Patrick Robert James's Avatar
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    Instead of separating the elements, you could use some light machine oil to fill the gap. It isn't a permanent solution, but it is fast and it works.

  7. #27
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    It doesn't sound like everything in the tutorial I wrote will apply to you in this case, however some of it may be of interest: http://www.fotomozaic.ro/ (look under Ultimele Tutoriale tab)
    If you or anyone here needs some Canada balsam, please let me know. You can dissolve it with several different types of solvents. You can also use a clear/high grade rosin if you need to...it will have about the same optical properties, actually.
    Jon

  8. #28

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    Good news. The Hasselblad 80mm front doublet came apart today in the jar of Methylene Chloride it's been in since 7-26-13. I'm going to be using some liquid Canadian balsam in a little bottle I bought from Canada on ebay.Hope it's the right stuff. I didn't like the idea of dissolving the hard sticks in my dusty house. I would have never been able to keep specks out of it as it dissolved.

  9. #29

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    Quote Originally Posted by Tom1956 View Post
    Good news. The Hasselblad 80mm front doublet came apart today in the jar of Methylene Chloride it's been in since 7-26-13. I'm going to be using some liquid Canadian balsam in a little bottle I bought from Canada on ebay.Hope it's the right stuff. I didn't like the idea of dissolving the hard sticks in my dusty house. I would have never been able to keep specks out of it as it dissolved.
    I got mine from the tree.

    Price was right, too.

  10. #30

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    Just to chronicle progress for future searchers, Now I have the 2 separated elements on the work table. I'm finding it strange that while acetone was ineffective at separating them and that methylene chloride (DCM) was what did the job, just the opposite on cleaning the residue. Soaking pieces of cotton with DCM, did practically nothing at scrubbing the glue residue off the face of the glass. Acetone seems much more effective at that. I have both elements clean now. I will go over then again, then do the standard Q-tip and cotton swab lens cleaning, and proceed with the balsam gum. So far, so good--no damage done.

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