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  1. #11

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    So, boiling it is. As far as the bobbing around, or letting the glass contact the metal of the cookpot, I plan to jam some cheap sponges in the bottom of the pot to pad it. Then, put the glass in the cool water and bring it to a boil in the outer pot. I'll be using my gas range, but I think the water insulating the bottom of the interior pot will keep the bottom of the pot from taking the brunt of the heat of the flame. I've been more worried about ruining the coating than cracking the glass. I'll use some sort of stiff padded tool to "fish around" the glass to dsee if it is actuall separating. If it does, I'll kill the flame and let the water cool down naturally. Avoiding thermal shock is the best policy.

  2. #12

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    Quote Originally Posted by Tom1956 View Post
    So, boiling it is. As far as the bobbing around, or letting the glass contact the metal of the cookpot, I plan to jam some cheap sponges in the bottom of the pot to pad it. Then, put the glass in the cool water and bring it to a boil in the outer pot. I'll be using my gas range, but I think the water insulating the bottom of the interior pot will keep the bottom of the pot from taking the brunt of the heat of the flame. I've been more worried about ruining the coating than cracking the glass. I'll use some sort of stiff padded tool to "fish around" the glass to dsee if it is actuall separating. If it does, I'll kill the flame and let the water cool down naturally. Avoiding thermal shock is the best policy.
    As I posted earlier I would not boil the lens except as a very, very last resort.
    You're so worried about damaging it, yet you start with the most agressive and fraught-with-potential-catastrophe method of separating it - which I also pointed out was apocryphal information. You have no experience recementing optics, yet you start with an expensive lens that is not your own.

    Good luck, it looks like you'll need it.

  3. #13
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    What I don't understand is, if you didn't know how to do the job and had no experience of ever doing it before, why did you accept it ?
    Ben

  4. #14

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    Quote Originally Posted by benjiboy View Post
    What I don't understand is, if you didn't know how to do the job and had no experience of ever doing it before, why did you accept it ?
    I'll answer that. He's a good buddy, but I believe he is also bipolar. He can be stubborn and has no sense of the value of money. He cannot be made to understand that the 3/32 ring of separation around the perimeter is of no consequence. To try to tell him makes him even more obstinate. To him the lens is already dead and he knows how much I have learned about these kinds of things from you people. Don't try to figure the logic.

  5. #15

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    Well, EvH, I caved into your pleas. The doublet is now sitting in a jar of acetone. I saw right off where it seeped into the separated areas around the perimeter. Whether it will continue its penetration of the cement to the center of the lens is something that leaves me in doubt. But we'll see. I suppose after a week and nothing is happening, no point in waiting a month, or a hundred years.

  6. #16

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    FYI After 8 hours soaked in Acetone, absolutely no signs of change. Will allow a week, then boil.

  7. #17

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    Quote Originally Posted by Tom1956 View Post
    FYI After 8 hours soaked in Acetone, absolutely no signs of change. Will allow a week, then boil.
    Is that lens cemented with balsam or UV curing cement? Balsam = acetone, xylene. UV/epoxy = methyl-ethyl ketone. It can take several weeks for any solvent to work.

  8. #18

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    Quote Originally Posted by E. von Hoegh View Post
    Is that lens cemented with balsam or UV curing cement? Balsam = acetone, xylene. UV/epoxy = methyl-ethyl ketone. It can take several weeks for any solvent to work.
    I have no idea what the glue is. Gut instinct tells me it's probably not gum. Lens is about a 1970 model, I'd say. And as an aside, I'm guessing you don't like hot water on account of possibly of glass cracking from thermal shock.

  9. #19
    Barry S's Avatar
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    I use xylene for 19th c lenses that I know used balsam cement. It can take a month or more for the solvent to reach the center of a doublet. Heat shock is a good way the shatter the lens and heating may not even be that effective for modern optical cement. Find the correct solvent and give it time.

  10. #20

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    I wonder how hot the Zeiss lenses on the moon got. I'd say near 200 degrees is a safe bet. Just talking.

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