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uncoated lens surface cleaning



 
 
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Old July 28th 11, 01:45 AM posted to rec.photo.equipment.large-format
Richard Knoppow
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Posts: 752
Default uncoated lens surface cleaning


"Cheesehead" wrote in message
...
I picked up an old uncoated Tele Xenar 360/5.5 today.
The front cell, inside surface needs cleaning.
What chemicals should I use to clean it?
It looks like some condensation was let sit for years.
It might require some serious buffing!

The last picture here shows the problem.
http://www.apug.org/forums/forum379/...tfit-more.html


Whatever you do don't buff or scrub it!
Most of this sort of haze will come off with ordinary
lens cleaner. I suggest "streak-free" glass cleaner. Other
good cleaners are dry isopropyl alcohol (isopropanol) and,
if you are able to remove the elements, acetone. Acetone is
a standard cleaner for lens assembly at the factory but will
dissolve some paint so be carful. For oily deposits you can
also try naphtha. Quite pure naphtha is available as
Ronsonol lighter fluid. Haze inside lenses is very common. I
don't know for certain what the source is but probaby either
something from the lubricant in the shutter or something
evoporated from the anti-reflection paint in the cells.
If you find you have a mold of some sort a mild solution
of bleach will help remove it but should be rinsed off
thoroughly.
Long standing mold or mildew can etch the glass. If the
surface has been etched there is no fix but re-polishing the
lens, provided the etching is not too deep. This is
expensive and may be more than the lens is worth.
I don't know how the Tele-Xenar is mounted but most
lenses have either a retaining ring on the front or a
threaded cap on the back. Retaining rings sometimes do not
have slots or dots in them and must be removed by using a
friction wrench. The are not hard to make but finding the
right kind of sticky rubber may be difficult.
Just to be clear, there is NO difference between
cleaning a coated and an uncoated lens, both the same.
Use a lint-free tissue. Kimwipes are fine. Use each wipe
ONE TIME and discard it. Wet the wiper, not the lens, then
drag the wiper across the surface and discard it. Use as
many as you need to do the job. The reason is because a
tissue or cloth, even a brush, can pick up particles of
abrasive grit and when re-used scratch the surface. That is
also why "buffing" or scrubbing is bad; only one bit if grit
is enough to ruin a lens. Some here will tell you they have
used the same bit of microfiber cloth for years and it never
damaged a lens. I would ask to look at the lenses.

--
Richard Knoppow
Los Angeles, CA, USA




 




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