Cleaning Fresnel ground glass

[Leonard Evens]

I have several Fresnel ground glass focusing screens for medium format
cameras. I'm starting to use these cameras after a long gap, and I'm not
sure I remember how to clean them. Any advice would be appreciated.
I do remember that one can ruin such a screen if one goes about it
improperly.

--

Leonard Evens l...@math.northwestern.edu 847-491-5537
Dept. of Mathematics, Northwestern Univ., Evanston, IL 60208

[Roland]

Leonard Evens wrote:
>
> I have several Fresnel ground glass focusing screens for medium format
> cameras. I'm starting to use these cameras after a long gap, and I'm not
> sure I remember how to clean them. Any advice would be appreciated.
> I do remember that one can ruin such a screen if one goes about it
> improperly.

If it's clean enough to use then don't clean it. If it's too dirty for
use then you should not worry about messing it up entirely. Clean your
hands thoroughly first so there is no trace of normal body grease on
them. Wash them two times at least and use plenty of soap. Then clean
the screens under a flow of warm tap water and use plenty of washing up
liquid several times and rinse after. Use you finger as the scrubbing
brush. The more times you clean it like that thwen the better it will
get. Let it drain to dry after shaking off excess water.

And if you ruin it them don't blame me. That's the way I clean ground
glass screens. But WHATEVER YOU DO - make sure your hands are very clean
first.

Roland

[Wilt W]

Caution, not all 'ground glass' is glass! If it's really plastic, I suggest to
not try cleaning it, else you run the risk of ruining the surface.

--Wilt

[Leonard Evens]

In article <20010816182312...@mb-ch.aol.com>, "Wilt W"
<wi...@aol.com> wrote:

My cameras are pretty old. I don't think they had invented plastic.
:-) :-)

[David Grandy]

While trying to remove some deteriorated rubber foam from a sliding roll
film holder I inadvertently got some of the cleaner (called Goop Off, if
you can believe it!) on the ground glass. It instantly removed about
half of the etching from said ground glass yielding it almost useless.

After calling around for a bit to see if I could find another 6X9
groundglass (which I couldn't) I figured that the old one would have to
do, messed up or not. But I wanted to remove as much of the greasy Goop
Off residue from the screen.

I removed the ground glass and to my surprise there was a Fresnel screen
behind it. I took each one and rinsed them off in lukewarm water. I was
shocked to see the groundglass's etching come back 100% as it dried! It
turned out that the Goop Off had gotten between the groundglass and the
Fresnel and "filled in" the etching and made it look like clear glass.
Once cleaned the whole thing was right back to where it was.

I was so excited about this that I took the ground glass off of my 4x5
and sure enough there was a Fresnel behind that as well. I had
inherited a stain on this ground glass that wasn't hurting anything but
was cosmetically ugly. Once again after rinsing and both the screen and
the Fresnel off in water the stain was gone and they were as good as
new.

I was gentle with the groundglass and Fresnel, and only washed them off
with water; but the medium format screen had had that Goop Off on it for
hours with no lasting side effects, so washing off your groundglass
(without Goop Off please) shouldn't hurt it a bit.

[Wilt W]

<< so washing off your groundglass
(without Goop Off please) shouldn't hurt it a bit.>>

Regardless of plastic or real glass, gentle wash and rinse off with distilled
water, with no attempt to wipe dry with a cloth or tissue, probably will do no
harm.

Drying with cloth or tissue will, at best, leave lint. Brushing off the lint
with a brush runs risk of the brush itself leaving dust in the texture.
At worst, abrasion renders the surface of the ground 'glass' plastic a mess
suitable for the trashbin (been there, done that!)
That's why I think that a rinse in distilled water, and a drip dry or blow dry
with warm air, is best.

--Wilt