Lens Element Separation Repair
robert hudyma
separated lens element. About 1/3rd of the element is separated.
The lens has excellent performance as a paperweight, it is optically
abysmal.
I know that very old lenses were cemented together with Canada Balsam
which will become soft and pliable in boiling water. It is possible to
separate the elements, clean them, cement and realign them.
Can you do this with a modern lens?? I understand that most of the optical
cements used in modern lenses are a UV cured acrylic compound. You drop
the adhesive on the lens, position the elements together, align them, and
cure the cement with an exposure to UV light. I have no experience
as to how you would go about taking apart the elements, cleaning them and
subsequently recementing the elements back together.
The modern optical cements are clearly easier to work with and superior to
Canada Balsam, but I imagine that any subsequent disassembly could be a
nightmare.
Does anyone know if UV cured cements will soften and become pliable
in boiling water? If not will they at a higher temperature?
Is it possible that they could be dissolved in a strong organic solvent such
as Xylene or Tolulene?
Or,... am I up the creek without a paddle??
mike...@austin.ibm.com
Look at the Shutterbug repair page. There is a guy up in Colorado that can
do this. He can tell you what is used to cement the elements together.
--
Michael (Mike) C. Dean
IBM - RISC/6000 Division
Austin, Texas.
Disclaimer - The opinions expressed in this append are mine alone.
Mark Walberg
(No, I don't work for Fargo.)
http://www.community.net:80/~curt/tools/new2.htm
robert hudyma
>some time now. but, i've seen nothing. i've got a couple of very old
>lenses on ancient cameras that i'd like to do something about too.
I think there were two postings to the newsgroups in the last
couple of days.
There is a place in Colorado that will repair a separated lens. His
ad is in Shutterbug in the repair section. I don't know what kind
of costs are involved.
The very old lenses can be repaired by yourself if you are careful.
(I assume no responsibility or liability if this technique fails. Each
lens is unique and has its own problems and "personality". However, it has
worked for me on old uncoated lenses).
Best also to experiment on a $10 junkbin type of lens first! (cheap
education) Also mentally prepare yourself for a total failure before you
begin (manage expectations).
The elements on the old lenses were cemented with Canada Balsam
(get from Edmund Scientific). Its still used today to prepare microscope
slides.
You need to be able to get the "optical cells" out of the brass mounts first.
Some were screwed in and others were held in place with a tar-like
pitch. Gentle force followed with WD-40 and boiling water usually
will do the trick. Be real careful not to apply too much force!
Once the cells are out, mark them along the edges with a pencil so that
you can realign them back together again. Put a pencil mark on the
brass barrel so that you can drop them in the exact same way too.
Wear a couple sets of latex dishwashing gloves so that you can put
your hands in the hot water.
Simmer the cells gently for a few minutes. A good idea is to put the
cells in the cold water and let it come up in temp slowly so that there
is no sudden thermal shock.
After a few minutes the cement should become "gooey" (scientific term)
and you will be able to slide them apart. Then just let the whole thing cool
down on its own (again no thermal shock).
You can clean off the remaining cement with an organic solvent like
acetone. (I have used this on uncoated lenses, I have not tried this
on coated elements). Note that these kinds of solvents are highly
flammable and exposure to these solvents is real bad for
your body. The key here is to use just a little bit in a well ventilated
area away from flames.
Then, in a dust-free place, you put a couple of drops of cement (either the
Balsam or better the UV cured stuff from Edmund Scientific). on the element
and position them together wobbling them around to make sure that the cement
covers the entire lens surface. (The next time I do this I will use a light
table.) Look carefully for bubbles, and grunge that could have been trapped.
If all is well the Balsam will harden on its own (I leave it overnight).
The UV stuff will cure on exposure to the proper light source (Sunlight is
rich un UV it should work too). A UV flourescent fixture is about $20 and
should work OK too.
After the cement has hardened you reassemble the lens. If you
need to replace the "black-tar" you may want to try some bees-wax
mixed with black pigment (art supply store). I have used this to rebuild
some old polarizer filters successfully. However the stuff used to seal
driveways is probably a closer approximation (yuuch). Come to think of it
the silicone based caulkings (available in various colours now) might
also do the trick (I'd be a little careful here because these caulkings
are acetic acid based and I'm not sure what kind of long term detrimental
effects this may have).
A few notes. The Canada Balsam will discolour with time (years) and can
crack and become brittle. I use it because it most closely approximates
the original materials. I am having problems with getting the Canada
Balsam and the optical adhesives shipped due to hazardous materials
restrictions. The optical sales person I talked to at Edmund scientific
suggested that I could use "Crazy Glue" since he believed that it is a
similar formulation to the optical UV stuff. The problem with this type
of adhesive is that it cures very fast, you may have only a few seconds to
work with (this is why the UV cured stuff is so neat you can work for as long
as you want before it hardens). I would think that the UV stuff is
more permanent but may be quite difficult to take apart (this is the
focus of my current investigation).
Another tip. Some of these lenses will have scratches/gouges on the surface
of them. (These lenses are deeply discounted by most vendors)
I am always amazed at how many scratches you can have
and not appreciably affect the performance of the lens. However,
the scratches "catch" the light and can induce nasty flare. There are
two things to do. First a good lens shade will help a lot to eliminate
this situation. Second you can paint the scratch with black paint. It looks
bizarre but stops the flare problem.
Good Luck...you'll need some of that too...
Robert Schmidt
>In article , rhu...@idirect.com (robert hudyma) writes:
>> I am conteplating the repair of a 300mm Symmar that has a partially
>> separated lens element. About 1/3rd of the element is separated.
>> The lens has excellent performance as a paperweight, it is optically
>> abysmal.
>>
>>
>> I know that very old lenses were cemented together with Canada Balsam
>> which will become soft and pliable in boiling water. It is possible to
>> separate the elements, clean them, cement and realign them.
>>
>> Can you do this with a modern lens?? I understand that most of the optical
>> cements used in modern lenses are a UV cured acrylic compound. You drop
>> the adhesive on the lens, position the elements together, align them, and
>> cure the cement with an exposure to UV light. I have no experience
>> as to how you would go about taking apart the elements, cleaning them and
>> subsequently recementing the elements back together.
>>
>> The modern optical cements are clearly easier to work with and superior to
>> Canada Balsam, but I imagine that any subsequent disassembly could be a
>> nightmare.
>>
>> Does anyone know if UV cured cements will soften and become pliable
>> in boiling water? If not will they at a higher temperature?
>> Is it possible that they could be dissolved in a strong organic solvent such
>> as Xylene or Tolulene?
>>
>> Or,... am I up the creek without a paddle??
Call Jeff at Ken Hansen Imaging in NYC. He's been repairing pro cameras
and lenses for over 25 years. He seems to know everything about these kind
of things. His number is (212) 777-5900 x114.
--
Robert Schmidt, New York City
rsch...@panix.com