Separating lens elements

[noacronym]

On my computer screen, I google up APUG and am brought to "todays posts" Despite all the categories I could select as a preference, I assume that any post in any category appears under "today's posts" for the broadest appeal, and presume from that we are all on the same page. That is my intent in the starting of this new thread; that I may hear stories and glean a procedure to deal with separating lens elements. For my purpose I bring up a Hasselblad 80mm lens in the old silver barrel where the front 2 elements are cemented. Being a world class do-it-yourselfer, I dare to think I could get those 2 elements apart, clean, and re-cement them. Right now the lens in my mind has separation on the outer 3/32 of the group. Ideas? Thank you.

 

[noacronym]

In addition, I'm thinking a several days' soak in either methylene chloride or acetone, but don't know that the lens coatings can tolerate.

 

[Dr Croubie]

Regarding the 're-cementing' bit, i'm wondering if the 'cement' holding the elements together (depending on whether it was made in the era of Coated, MC, or Today), might it have some sort of special reflective properties like coatings too? Or is it just a single type of any-old-lens-cement-will-do?

 

[Arvee]

I repaired an enlarging lens by simply putting the lens pair in the oven at the lowest temp, 170 degrees, IIRC. About 45 minutes and the cement softened and I was able to slide them apart and finished cleaning the cement with acetone. You need Canadian balsam cement to put them back together but it is very difficult to do so without getting air bubbles, in which case you have to start all over again. Then there is the collimation/element centering issue to deal with. There are articles on the web to guide you on the re-cementing process. Good luck!

With your description of the separation being so small at this juncture, I would leave it alone and use it at apertures smaller than wide open. I expect you will see no degradation at smaller apertures. Chances are the attempt to repair yourself will result in your sending the lens out for repair at a cost greater than buying a used lens in good shape.

 

[EdSawyer]

I would use a modern UV-curing cement for reassembly. Edmund OPtics sells several varieties.

-Ed

 

[Dan Fromm]

Go here http://web.tiscali.it/memoriediluce/, click on Strana Roba, click on Como riparare lenti scollate. If you don't read Italian, Google Translate will help you understand the text.

In addition, I'm thinking a several days' soak in either methylene chloride or acetone, but don't know that the lens coatings can tolerate.

Coatings are resistant to most solvents. Just don't use HF.

Regarding the 're-cementing' bit, i'm wondering if the 'cement' holding the elements together (depending on whether it was made in the era of Coated, MC, or Today), might it have some sort of special reflective properties like coatings too?

Nope. If a lens shows rings of fire, it has separations.

 

[rjbuzzclick]

Jon Goodman has a page on this:

http://www.fotomozaic.ro/artikel.php?s=1&categ=21&idstory=412