Corrosion/gunk on film rails

[dana pionek]

Hi,

 

I just happened to pick up a really nice Pentax Spotmatic body for a really

good price. Upon initial inspection the camera seems near flawless except for

one thing - there seems to be some mild corrosion (or maybe gunk buildup from

film emulsion)on the film rails (the pressure plate rails are perfect). I

assume that this is due to storing the camera with film in it. I ran a roll

of film through it and the rails seem to have scratched the film along its

whole length near the sprocket holes. Does anybody have any do-it-yourself

suggestions on dealing with this problem? I have tried acetone on a Q-tip but

didn't get anywhere. My next thought was to cut a piece of glass that would

span the two rails then use some spray-tac to attach a piece of 1500 grit

sandpaper to the glass and use it in a similar fashion as a block sander to

polish the rails. I realize that the tolerances of the film rails to lens

mount distance are very critical and I don't want to ruin the camera by taking

off too much surface (although I seriously doubt 1500 grit is going to take

off that much). Any suggestions/warnings? Should I try the block sanding

idea? Send it to a pro to have the problem fixed? Or should I just live with

some mild scratching on the film near the sprocket holes? Any help is greatly

appreciated.

 

Thanks

[john_shriver]

Yeah, sounds like some sort of corrosion. Of course, that area of the film doesn't image. On the other hand, the corrosion has probably increased the film-to-flange distance.

 

Once they are done being polished, the camera can be re-collimated. Probably a small adjustment to the tilt of the mirror to equalize the flange-to-film and flange-to-focusing screen distance. (Well, that's how it's done on a Topcon Super D.) If that's not adjustable, the focusing screen would need re-shimming.

[donnie_strickland]

If it was mine, and if it won't show up on the print/slide, I'd let it be. I have a few cameras like this and it's not a problem.

[curt_saxton]

Sometimes you'll get lucky using something very mildly abrasive like an eraser for ink, or a tiny bit of tooth paste or automotive paint rubbing compound on a cotton swab. Just make sure it's a TINY bit and you don't get any in the shutter.

[sw12dz]

I wouldn't use sandpaper. I have had similar problems with rough film rails and rollers. I used a metal polish (ie: Simichrome or Meguiars Mirror Glaze All Metal Polish) and achieved very good results.

[luis triguez]

I wouldn`t use sandpaper either. I`ll try with any gel paint stripper on a Q-tip. You set on the rails, carefully, the gel, and in a few minutes you can take off the corrosion. Maybe you need to repeat a couple of times.

 

I did it this way when I changed the leather from an old Canon with a lot of corrosion in the body. It worked successfully

 

.

[winfried_buechsenschuetz1]

Most camera bodies are made from aluminium (alloy), and uncoated alloy is quite susceptible to corrosion when it gets humid.

 

If the scratches on the film are NOT inside the image frame, I would not bother too much. You might try to remove the corrosion spots with a glass fiber eraser, the thing (formerly) used by draftsmen to erase ink.

[tony_lockerbie]

I have used the finest grade of wet and dry sandpaper on some rails and rusted rollers and found it to be very effective. Just be sure to remove all the loose particles carefully before using the camera.

Tony

[dana pionek]

Update -

 

I tried the eraser - didn't do a whole lot for my camera. Was thinking about the car rubbing compound but was worried about getting a bunch of goop in the shutter. I ended up trying the sandpaper idea (only because I had some 1500 grit wet/dry paper laying around) - It worked really well (I lightly wetted the paper and only took a few light/even laps - just enough to knock off the corroded high spots without doing too much to the base metal). I Put a roll of film through the camera and developed/printed it - focus seems spot on and the negatives had significanly less scratching on them. BTW - the glass "sanding block" really helped as far as controlling how even the sanding strokes are. I tried it without the block first and quickly aborted the mission - there was just too much of a chance of totally rounding out the rails.