Re: [Leica] Fogging

["Dan Post" <dwpost@email.msn.com>]

Karim-
I found a really nice Summaron 35 LTM lens. Cosmetically, almost mint, and
really a nice compact lens- and fairly sharp. It too had 'fogging', as do
many, many lenses from the 50's when they used a lubricant similar to
Nyloil- the watch and clock lubricant made from whale oil.
Unlike petroleum greases that are composed of hyrocarbons of various
molecular length, and different evaporation rates- and which tend to harden
of a few years time, the whale oil lubricants were composed of molecules
that are of a fairly consistant weight, complex esters that tended not to
'dry' or harden, so the life of the lubricant was much longer, and more
stable at different temperature extremes.
They have a tendency, over time, to migrant, sublimate, and like the greasy
film on your kitchen walls, from cooking, these oils, after 40-50 years,
tended to get on the glass.
My personal experience is that this oil, and sometimes edge separation is a
bigger problem by far than 'fungus', even in the south whare I live. The
upside is that the oil can be cleaned off, relatively cheaply, and the
separation can be repaired (not so cheaply, but can be repaired). In fact, I
have bargained the price down on a lens by $150 or so, knowing that for
$75-85, Sherry could set it right!
You will be surprised what a difference a good cleaning will make! My lenses
usually gain at least one stop of contrast, and the sharpness improves
noticably as well.
Dan

- ----- Original Message -----
From: Karim H. Karmali <kkarmali@home.com>
To: <leica-users@mejac.palo-alto.ca.us>
Sent: Sunday, August 08, 1999 12:11 PM
Subject: [Leica] Fogging


> Is there any way of telling whether the fogging you find in some older
> lenses can be removed or not.  I recently purchased a very clean example
of
> an older Summaron 35/3.5 for my M3.  Unfortunately, both the spectacle
> viewfinder attachment and lens appear to suffer from some fogging.
>
> Thanks for your thoughts.
>
> Karim
>
>
>