Cleaning focusing screens

Pentode · Aug 28, 2018

My recent acquisition of a Minolta XK made me dig out the accessories I had stashed when I sold my last one over 20 years ago.

In the stash was a batch of four focusing screens. The packaging for these screens back in the ‘70s included pink foam rubber which has now deteriorated into a slightly granular pink goo. This goo has stuck, in part, to both the fresnel side and the convex side of the screens.

I’m fairly certain the fresnels are plastic and I’m pretty leery of damaging the surface of them. I also suspect that any liquid I might attempt to clean them with would end up between the plastic and glass by capillary action and might carry the dreaded pink goo with it.

Anybody have any ideas about removing pink goo from focusing screens?

I’m careful and methodical. I’m good with my hands. I have small tools and an ultrasonic cleaner. None of that does me any good, however, unless I know what I’m getting myself into.

Anyone with first-hand goo experience have any suggestions before I ruin a screen?

Thanks!

Scott Micciche · Aug 28, 2018

You could try putting the screen in a freezer for a while, which might make the goo fall apart; easier to remove.

Pentode · Aug 28, 2018

Scott Micciche said:
You could try putting the screen in a freezer for a while, which might make the goo fall apart; easier to remove.

I actually thought about that. It might be worth a try. I don’t see it doing any harm, anyway, and that’s the goal.

Pentode · Aug 30, 2018

Just a little bump:

Anybody else have pink goo experience/ideas?

Thanks!

Scott Micciche · Aug 30, 2018

I've never had pink goo, but I have had bits fly up and stick to the underside of several SLR cameras. I used the freezing technique on my Nikon E screen and just dabbed a q-tip with isopropyl on the goo and it came right off. Do you have a photo of this goo and its placement?

benjiboy · Aug 30, 2018

This stuff is magic for removing sticky stuff they sell it at Amazon .com goo gone adhesive remover.

Pentode · Aug 30, 2018

benjiboy said:
This stuff is magic for removing sticky stuff they sell it at Amazon .com goo gone adhesive remover.

It is, indeed, amazing stuff but I wouldn’t go anywhere near a fresnel focusing screen with it. Thanks for the suggestion anyway.

Pentode · Aug 30, 2018

Scott Micciche said:
I've never had pink goo, but I have had bits fly up and stick to the underside of several SLR cameras. I used the freezing technique on my Nikon E screen and just dabbed a q-tip with isopropyl on the goo and it came right off. Do you have a photo of this goo and its placement?

I don’t have any goo photos but I could produce some, disgusting as that sounds.

The freezing idea is very intriguing.

Pentode · Aug 30, 2018

nusproizvodjac said:
I had a beater XG to practise disassembly/repair/stuff l wouldn't subject other cameras to, and it had a rather dirty focusing screen, with particles that wouldn't come off with a blower bulb. Following various tutorials both on this forum and the internet,
l tried washing the screen in a cup of warm water with a drop of dish soap and rinsing with distilled water. The particles did come off nicely, but the edges of the screen turned dark, and at the top there's something that looks like a water spot.
You can still focus with this screen, it's accurate and all, but it's very nasty looking. So, unless you want to make your screen even worse, don't wash it under any circumstances.

Thanks for that tip. That’s the type of outcome I hope to avoid!

shutterfinger · Aug 30, 2018

In my experience with Goo Gone it left an oily residue. I would not use it anywhere near a camera or any thing photographic.
I use Motsenblockers Lift Off #2 https://www.amazon.com/MOT40701-Mot...e=UTF8&qid=1535660778&sr=1-1&keywords=liftoff . Excellent stuff, does not leave a residue but wash treated area with Isopropyl Alcohol before applying new glue. It might cause a sandwiched focusing screen to separate if it penetrates the edges.

CMoore · Aug 30, 2018

Are focus screens sensitive to cleaning...ate they easily damaged.?

shutterfinger · Aug 30, 2018

CMoore said:
Are focus screens sensitive to cleaning...ate they easily damaged.?

Yes. They're soft plastic, easily scratched, similar to front surface mirrors.

MattKing · Aug 30, 2018

CMoore said:
Are focus screens sensitive to cleaning...ate they easily damaged.?

shutterfinger said:
Yes. They're soft plastic, easily scratched, similar to front surface mirrors.

And even if you don't damage them, it is very easy to end up with the "dirt" being just smeared all around, and even more objectionable than when you started.

CMoore · Aug 30, 2018

Weird...never dawned on me that they were plastic...but i guess they are.?
I am used to the screens for Canon and Nikon that are in a frame.
But the Olympus screens have no frame. I remember breaking one of the Pull Tabs off the Oly Screens.....just plastic and it snapped right off.

Scott Micciche · Aug 30, 2018

The Fresnel side can also fill the surface with residue. Even lens cleaning solution can harm them. Eclipse solution, mostly used for digital sensors, might be a good option as it leaves nothing, but it might smear goo around. Lighter fluid on a pec pad, soaked on the goo, might lift it off as well.

cooltouch · Aug 30, 2018

I'll pass along a tip I was given by a seasoned old pro some 35 years ago. First, though, let me state that if you have a two-piece focusing screen, if it were me, I'd see how difficult it would be to take it apart and clean the pieces separately. Second, a pair of white cotton darkroom gloves or similar might not be a bad idea. Now, as for the tip, what she recommended I do to clean focusing screens was to dump the screen inside a film canister, add a single drop of dish detergent and fill it with warm water, enough to cover the screen. Cap the canister and shake well. Then rinse thoroughly. Let air dry. I suppose it's also worth mentioning that the rinse water might should be distilled so as not to leave any spots behind. I've been using this technique ever since it was first passed on to me, and I gotta say that it's worked well for me.

Dish detergent is mild, yet does an excellent job of cutting through grease or oil -- and probably goo as well.

I'll pass this one on as well. I ran into a situation where I acquired a Canon FTb, with its non-removable focusing screen, but its mirror bumper had turned to goo. A previous owner had managed to smear some of it on the bottom of the focusing screen. I took a cotton swab and some 70% isopropyl alcohol, and attacked the smear. It literally dissolved away. The screen was restored to perfect clarity. Dodged the bullet on that one, I've always felt.

Poisson Du Jour · Aug 30, 2018

Fill the sink with warm (not hot!) water with dishwashing liquid. Dunk the focusing screen in and leave it there for 30 minutes. Retrieve, wipe off the gunk and air dry. Finish up with a thorough wipe over with an antistatic cloth (e.g. Ilford's).

Vincent Peri · Aug 30, 2018

"Are focus screens sensitive to cleaning...ate they easily damaged.?"

shutterfinger said:
Yes. They're soft plastic, easily scratched, similar to front surface mirrors.

Just a point of clarification, all Nikon F cameras (F, F2, F3, etc) have glass focusing screens.

shutterfinger · Aug 30, 2018

Scott Micciche said:
Lighter fluid on a pec pad, soaked on the goo, might lift it off as well.

The Naphtha in lighter fluid will likely damage plastic focusing screens.
Lighter fluid is only safe to use on cameras when left in the can, preferably left on the store shelf. A pint of 90% Isopropyl Alcohol will serve you better.

Scott Micciche · Aug 30, 2018

shutterfinger said:
The Naphtha in lighter fluid will likely damage plastic focusing screens.
Lighter fluid is only safe to use on cameras when left in the can, preferably left on the store shelf. A pint of 90% Isopropyl Alcohol will serve you better.

Ah yes, I forgot about the plastic aspect. Good catch!

cooltouch · Aug 31, 2018

Vincent Peri said:
Just a point of clarification, all Nikon F cameras (F, F2, F3, etc) have glass focusing screens.

Just to add to your clarification. Canon F-1 screens (both new and old) are also glass. They're two-piece though . . . or at least the old ones are, so they should probably be dismantled, if possible.

CMoore · Aug 31, 2018

Vincent Peri said:
"Are focus screens sensitive to cleaning...ate they easily damaged.?"

Just a point of clarification, all Nikon F cameras (F, F2, F3, etc) have glass focusing screens.

OK.....that was part of my confusion. Most of my experience is with the Nikon F2 and Canon F1.
Not trying to make a Mountain out of a Mole Hill, but.......was it tricky to develop a "Plastic" focus screen.
Did it need to be, or is there such a thing as Optical Grade Plastic.?

sissysphoto · Aug 31, 2018

I've had good luck using 1 of 2 methods. both entail an artist or modeler's paintbrush and warm water at the kitchen sink. The 2 method part being either Ajzx dishwashing liquid or Awsome cleaner. the Awsome cleaner being a slightlly weakened version of purple soap which is a degreaser found in auto parts stores.

However this thread brings to mind the videos i've seen on the use of white glue or carpenters glue used to clean vinyl phonograph records.

shutterfinger · Aug 31, 2018

CMoore said:
Did it need to be, or is there such a thing as Optical Grade Plastic.?

Kodak disposable cameras used plastic lens and likely other models and brands, so, yes there is such a thing as optical grade plastic.

CMoore · Aug 31, 2018

shutterfinger said:
Kodak disposable cameras used plastic lens and likely other models and brands, so, yes there is such a thing as optical grade plastic.

That is certainly true.
But those were "Cheap" cameras.
Then again, maybe Plastic/Acrylic...whatever it is...is a fine materiel, i have No Idea.
I guess what i should have asked is.....Why plastic.?
I am NO tech or engineer, but i would think glass would be just as good as plastic for the purpose of focusing...and a lot better where Maintenance/Cleaning is concerned.?
Was it simply a cost thing.?
Maybe the camera maker figured the screens would never get very dirty and need cleaning.?

Cleaning focusing screens

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