It is also common in factory service (Nikon & Olympus) to use face oil
on the mirror to remove fungus. (Wait while screaming stops) There have
been many assumptions made about proper/improper cleaning methods. If
the factory does it, then that's an effective way to do it.
Optical parts are no where near as fragile as some people think they
are.
John
Chuck Norcutt wrote:
>
> Joel Wilcox wrote...
>
> I herewith quote Dr. John from about one year ago on this topic and a
> more agressive cleaning method:
>
> "Lens tissue wrapped around a narrow flat object, dipped in denatured
> alcohol
> works for me. Don't press too hard on the mirror as the silver can come
> right
> off if you trap a piece of grit in there. If there is old mirror foam
> in the
> corners, that'll smear around alot and you'll have to clean it 10 to 20
> times
> to get it all off.
>
> John
> Camtech"
>
> My recollection is that several list members were appalled at this
> method
> of cleaning the mirror. I've had several cameras through John's shop and
> the mirrors all have come back looking good.
>
> ----------------------------------------------------------------------
>
> The proof is in the pudding. The mirrors have all come back looking
> good. John speaks loosely of "silver" on the mirror. Since long before
> the OM-1 was made first surface mirrors have typically been coated with
> aluminum and not with silver. Silver is an excellent coating for mirrors
> (for the first 5 minutes) because it has a higher reflectivity. But...
> it's soft and quickly tarnishes. When used on a mirror it must be
> overcoated.
>
> Aluminum, also "tarnishes" but the coating that forms when exposed to
> the air is aluminum oxide. The aluminum oxide layer is clear and
> extremely hard... which is why aluminum oxide is also used as a grinding
> compound. It's harder than glass.
>
> Of course, both the aluminum coating and the oxide layer are extremely
> thin and some little piece of grit can cause a scratch. I wouldn't
> suggest using a liquid unless it was really needed but, as long as
> you're not dragging grit around the surface, cleaning with a liquid like
> lens cleaner should cause no harm.
>
> Chuck Norcutt
>
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