Lama,
In essence, the difference between a front surface mirror
and one like a bathroom mirror is where the glass is coated.
The Bathroom mirror is coated on the back surface, and so when
you use your towel to wipe the steam off, the towel and such
does no damage to the aluminum. IF any damage is done to the
glass itself, you probably won't notice it.
However, front surface mirrors have the aluminum coating on
the front. The aluminum is very thin and very fragile, and so
easy to scratch and/or distort. Aluminum is softer than silica
(sand) but harder than cotton.
In addition, the bathroom mirror does not need to have a precision
surface (low magnification). If you look carefully, you can detect
the strain and surface irregularities, just like you can in most
house window type glass. Front surface mirrors typically have been
ground and polished to a smoothness measured in nanometers. I
doubt the mirror in an OM camera reaches nanometer precision, but
the basic principle of using reasonable care with it does apply.
Please, I just "scratched the surface" on the above discussion,
but would be willing to go further off line if interested.
Tom
Tucson, AZ
>Date: Tue, 15 Apr 2003 22:00:42 -0400
>From: "Lama-Jim L'Hommedieu" <lamadoo@xxxxxxxx>
>Subject: Re: [OM] Best way to clean OM-1N mirror
>
>I've already spoken my peace but I'm wondering if one of our
>astronomers would describe how a front-surface mirror is made?
>How is it different from a bathroom mirror?
>
>Advice on keeping a clean mirror? Body cap.
>
>Lama
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