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Hank
Tinkerer
Username: Hank
Post Number: 17
Registered: 07-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, July 19, 2011 - 06:16 pm: | 
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Ok my friends what do we know about heating elements up to separate them ??? Then doing a recement. Let me explain, I have a Summilux element with fungus in between the two cemented elements. Its an early lens from 1960. In Thomas Tomosys Leica Guide he says that if it is an early lens then its cemented with Canada Balsam and that its easy to just heat it up to 150f and separate the element. Then clean it and then re-cement with Norland Optical Adhesive and then harden with a UV light. I don’t have optical adhesive or a UV light... I will have to order it. Has anyone had any experience with separating and cleaning Leica cemented elements? Please advise. Thanks
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Old_school
Tinkerer
Username: Old_school
Post Number: 103
Registered: 04-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, July 26, 2011 - 01:03 pm: |
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Hank: I tried to post a comment a while back & it did not take! This is not the first time, but oh well! I did some optical grinding at the Hughes Malibu for a brief time & watched a few techniques. The one that stands out in particular is a good size diameter of calcium chloride (I think). The technician had placed it on a hot plate to heat up & adhere for grinding & polishing. It cracked & he cried, but the boss said that was the character of that material & to finish the procedure. Anyway, they did a lot of optics in salt which in itself fascinated me, real neat & interesting. The thing I would be a little cautious on is making sure that the glass is not cold when placed on the heat so it does not shatter from the shock. I think that if you place them in between the palms of your hands to warm it up first may be a good idea. Just a thought! To check if it is separating at the recommended temperature you might consider a few wood dowels or chop sticks with a slight beveled edge. Once you get them separated, let them cool down in a draft free area too. Is there a cleaning solution he recommends to clean the old Balsam off with & could you soak it in that solution for an extra special long time instead of heating them up? Just a thought. Don't know if this helps?
The Best Mike... |
Neuberger
Tinkerer
Username: Neuberger
Post Number: 54
Registered: 01-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, July 26, 2011 - 01:56 pm: |
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Why would anybody change a successive formula? If the orininal glue was Canada balsam there is no reason using anything else than the original stuff; Canada balsam at least offers a second - or third chance.
Regluing lenses is not easy, without experience, and that means practice - you will probably end up with a complete mess of sticky substance all over the workplace. I have no knowledge of tinkerers successfully using UV curing glues, but even if I had I would not use them, as most new glues are toxic.
After a whole lot of reglued bino (up to 80mm front lens pairs, without air bubbles between then!) and mostly Canon and Yashica rangefinder lenses I know what I am saying.
For the separation of the glued lens pairs try an additional acetone bath overnight instead of only heating the lens. If that does not help getting the glass elements apart the glue used will probably withstand all other repair attempts and is definitely not Canada balsam.
A quick search on the net and/or this forum's archives will help clarify the matter. |
Old_school
Tinkerer
Username: Old_school
Post Number: 104
Registered: 04-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 27, 2011 - 08:26 am: |
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Neuberger: I can understand what you are commenting on & can agree somewhat on the Canadian Balsam. But on the other hand, some of the new adhesives are not likely to yellow with age or attract the mold or fungus that he is trying to clean up. I think! On that note, a test run could not hurt. Hank might try cementing a couple of inexpensive mineral glass watch crystals together for practice. For what it is worth, one of the Japanese watch Co use a sapphire top crystal cemented to a mineral glass one to reduce the cost & promote a sapphire crystal. This exercise should be noted as some of the eyepieces are showing a separation of the elements causing a cloud & Newton rings noticed as a rainbow aberration in the finder. Some due to age others due to cleaning solutions seeping into the cement causing a deterioration of the cement.
The Best Mike... |
Old_school
Tinkerer
Username: Old_school
Post Number: 105
Registered: 04-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 27, 2011 - 11:37 am: |
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Neuberger: I thought of this after the last post: Before Hank does the cementing, does anyone know if the refractive index of the UV glue will change the optical light paths & how would you compensate for it? This could be another reason to stay with the original Canadian Balsam. The older Leica RF's dim on the yellow due to the degradation of the C/B also!
Just a thought!
The Best Mike.... |
Jeffk
Tinkerer
Username: Jeffk
Post Number: 3
Registered: 10-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, October 17, 2011 - 09:10 am: |
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I don't have experience separating old lens elements, but I do have some experience bonding optical components. You probably don't want to use a UV-cure glue for this application - it's useful for glue jobs on parts that have been fixtured in place, because once you decide to press the button and start curing it can be over with relatively quickly, which is nice if you're on a production line and time is money. But you need a very bright, directed UV lamp, and for a hobbyist spending his own money it's expensive and possibly dangerous. There are many other optical glues, mostly epoxies, that cure over time without UV. There are index-changing components you can add to a glue to alter it's refractive index, but I suspect that for this application it won't make any difference - the glue layer is very thin, and almost certainly is not an integral part of the optical design. |
Br1078lum
Tinkerer
Username: Br1078lum
Post Number: 156
Registered: 11-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, October 17, 2011 - 12:01 pm: |
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Micro-Tools sells the glue in smallish tubes, and says that you can cure it by placing it in sunlight.
http://www.micro-tools.com/store/home.aspx
Also, for heating the elements, a salt bed is good to use, and start with everything at the same (room) temperature. This way, there is no heat gradient spike to possibly crack the elements.
PF |
Jeffk
Tinkerer
Username: Jeffk
Post Number: 7
Registered: 10-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, October 18, 2011 - 03:29 pm: |
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Also, note that the lens surfaces need to be scrupulously clean before you attempt rebonding. I used to use reagent-grade acetone for this sort of work, assembling interferometer components for product prototypes. You would also need to take some care in recentering the lenses - a cheap HeNe laser is useful here, you can look at the various backreflected ring patterns (projected back on a piece of paper around the laser, or on a wall) and adjust until they are coaxial. |
