Pressure Plate Restoration

[farlymac]

Anyone have a recommendation for how to restore a rusty film pressure plate? Is gun bluing material suitable, or just a bit of clear coating? I worry about the bright areas affecting the film if I just polish out the bad spots.

PF

 

[kbg32]

I would try to find a good replacement. Refinishing could create problems with scratching the film.

 

[_goodtimez]

Wouldn't be easier and more straighforward to make one out of stainless steel?

 

[oftheherd]

Depends on how bad the rust is I expect. If it requires Navel Jelly, it's probably going to be tough to fix. But I have seen cameras with silvery pressure plates and it apparently not a problem. Very few films don't have a good anti-halation backing that will prevent any relections during exposure.

To prevent scratching, try to use Crockas(sp) Cloth, or the absolute finest sandpaper you can get. We used to us Crockas Cloth in the military for removing rust without removing blueing. I have found it and other very fine sandpaper in Ace Hardware stores.

 

[BobYIL]

Anyone have a recommendation for how to restore a rusty film pressure plate? Is gun bluing material suitable, or just a bit of clear coating? I worry about the bright areas affecting the film if I just polish out the bad spots.

PF

Before all be careful while trying to sand the rusty areas as the pressure plates are made of thin metal and they get warped rather easily. At best, use a wet-abrasive paper above 1000 grit (any sort does the job, even a half-sheet does the job) put the paper on a wet glass and grind your plate wet (!) until only the rust disappears. This will maintain the flatness of the plate (just like lapping). I do not think you'd need to have it black-oxidized again.

 

[nikon_sam]

Would #0000 Steel Wool work in this situation...???
It's some very fine stuff...

 

[_goodtimez]

BTW, all my parked cameras are kept using a thin carboard plate (business card thickness) between the pressure plate and the film rails, to prevent corrosion.
Most new cameras were delivered with some kind of isolator between the plate and the film rails.

 

[Sparrow]

... refinish with fine wet'n-dry paper then "blue" the new surface?

... used wet on a piece of glass with a little detergent in a figure-of-eight motion would ensure a smooth and flat result

 

[Ken Smith]

Would #0000 Steel Wool work in this situation...??? It's some very fine stuff...

Yes it would. I use it to clean off the old faded bluing off the nickle silver ferrules and reel seat hardware on my cane fly rods, followed by a fine polishing with Flitz metal polish. And nickle silver is softer than the metal in the pressure plates.

The big question is whether or not the pressure plates are sheet aluminum or steel. Aluminum does not blue, but you can anodize it. Steel you can easily blue using Birchwood-Casey's Gun Blue but it would take multiple coats to get it dark enough and then it's only a dark blue and not actually black. There are bluing agents out there that actually get to a black, but they are highly toxic, come in very small amounts, and require ground shipment.

The key to getting a consistent uniform color with any bluing agent is to completely remove the old finish, polish the metal, and then completely clean the surface with either acetone or Denatured Alcohol. The slightest touching of a finger to the surface will deposit enough body oil to thwart a uniform bluing process. I can't stress enough how clean the metal surface needs to be - sterile clean or you will get variations in the bluing.

And one last thing, the passing of film across the pressure plate will eventually
wear the bluing to where you will need to repeat the bluing at some point in the future.

To be honest, I think a baked on hard finish would be the best for long term wear.

 

[BobYIL]

Would #0000 Steel Wool work in this situation...???
It's some very fine stuff...

The point is to maintain its flatness while sanding/cleaning. Any abrasive can work however with wet-sanding on a glass the OP would hold it flat against the abrasive surface so that only the peaks (rust) can be sanded and in the meantime its flatness would be retained.

 

[agour]

you could sand it down with fine sandpaper, to an smooth even level. Then powder coat it to get it black again?
sure powder coating might be a bit expensive, but its much thinner than a coat of paint and shouldnt affect focus.
Im not too sure this approach would work, just throwing it out there!

 

[BobYIL]

you could sand it down with fine sandpaper, to an smooth even level. Then powder coat it to get it black again?
sure powder coating might be a bit expensive, but its much thinner than a coat of paint and shouldnt affect focus.
Im not too sure this approach would work, just throwing it out there!

😀 😀 😀 (Thank you..)

 

[farlymac]

That's a lot of good ideas, some of which I had thought about already. I like the powder coating idea best. But I do wonder just what was originally used by the manufacturers. I cleaned off the plate in my Vito B with just an eraser, and so far it looks good. The Agfa Karat 36 I'm presently working on though has much more widespread rust, though it doesn't look as pitted as the Vito was. Got plenty of 1500 grit paper left over from working on the Mercury II, and can easily get some 3000 grit if needed. I don't know how small scratches in the clear side of a negative would affect the overall image, as it's usually problems with the film gate that cause the most problems, gouging the emulsion. And the blueing approach would tend to wear off after a while. I might check with some local metal shops to see what is being used these days besides powder coating. Or I might try thinning down some flat black, and bake it in the sun for a few days.

Thanks, everyone.

PF

 

[BobYIL]

That's a lot of good ideas, some of which I had thought about already. I like the powder coating idea best. But I do wonder just what was originally used by the manufacturers. I cleaned off the plate in my Vito B with just an eraser, and so far it looks good. The Agfa Karat 36 I'm presently working on though has much more widespread rust, though it doesn't look as pitted as the Vito was. Got plenty of 1500 grit paper left over from working on the Mercury II, and can easily get some 3000 grit if needed. I don't know how small scratches in the clear side of a negative would affect the overall image, as it's usually problems with the film gate that cause the most problems, gouging the emulsion. And the blueing approach would tend to wear off after a while. I might check with some local metal shops to see what is being used these days besides powder coating. Or I might try thinning down some flat black, and bake it in the sun for a few days.

Thanks, everyone.

PF

Powdercoating can not be an alternative: Prepare yourself to be told that you have to strip, scrape everything on the plate down to metal; sides and backside too. Further, powder coating is performed (curing after coating) above 350F, this thin plate will definitely warp... And the last; the thickest surface coating is powder coating; it's not a garden furniture.

Acrylic matt spray baked in a kitchen oven to not exceed 180F could be the most practical way, IMO..

 

[Murray Kelly]

I remember using Oxalic acid to dissolve rust off tools. Very effective and rewarding.
Mostly you can pull the pressure plate off the back of the camera. If you can you could try leaving it in a cup of water with a teaspoonful of Oxalic acid added.
Afterwards, give it a good rinse and then decide if you need blackening. Texta?
There is usually a space between the level of the film rails and the film gate rails so the film theoretically doesn't actually touch the back plate at all.
I have used black 120 backing paper over the pressure plate to kill flare when using Polypan-F (no anti-halation backing) and there was no problem with scratches.

Murray

 

[farlymac]

I got to looking at it, and the plate in the Karat is dimpled quite a bit, which should give it some rigidity. And since I'm not going to be shooting any old film like Murray's Polypan-F, I just took the fiberglass pen to it. Whatever coating is on it is in a very thin layer, so I would think some really thin flat black will do later on. It's been taking too long to get it back together, so I'd rather see if all is working well before doing a paint job on the plate, and holding up final assembly anymore.

PF

 

[Sarcophilus Harrisii]

Not having any actual experience reclaiming a worn pressure plate, FWIW--if any abrasive action was being considered I would be inclined to make use of a sheet of scrap glass as an affordable means of utilising a reasonably flat surface to keep the plate true. And at the risk of stating the obvious, if you must try to dress the surface of the plate: start off with the least abrasive compound available and work up from there to coarser materials, if required. Where to start? I've used aluminium oxide to make ground glass and this is very fine (there are of course different grades of oxide too, I used two in series). What about toothpaste? I'm not sure where it sits in relation to some of the industrial alternatives but it must be towards the finer end of the scale?

It's an interesting discussion because it is an aspect of camera restoration not often talked about. Let us know how you get on with the camera, please.
Regards,
Brett

 

[Greyscale]

Maybe a thin coat of black lacquer or epoxy paint, and polish to a high shine with 0000 steel wool or pumice, and a final polish with rottenstone until it is smooth as glass? That should be quite durable.