How to clean corrosion or fungal deterioration on top plate of my M7?

[AnakChan]

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8 years back, I sent my M7 to have an à la carte top plate done to commemorate the passing of my dad. In recent years I've noticed either some kind of corrosion or fungal-caused deterioration and have tried cleaning with isopropyl alcohol (64%) which has cleaned up most but not all. This is probably the 2nd or 3rd time I've tried cleaning in the past 4 years there are some persistent spots that can't be removed.

Anyone know what this is? I thought the top plates were resistant to corrosion or to any kind of fungal growth. Any recommendations on how to clean this? Going to my local Leica reseller, they could only recommend isopropyl alcohol. I don't want to end up rubbing off the black lettering in trying to clean this up too so not certain how to be careful in the cleaning.

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[250swb]

Strange, unless the photo is taken at a bad angle it doesn't seem to be the usual bubbling of the chrome and the spots appear to be on the rewind crank and the hot shoe as well. You could try a 50/50 mix of hydrogen peroxide and ammonia gently applied on a soft cloth. It's the same solution that can be used to clean fungus off a lens. I'd definitely get rid of the half case if it's leather, and wouldn't keep the camera in any sort of leather bag or case. And leave it standing on a windowsill every time you aren't using it so UV light can kill any fungus.

Edited December 28, 2023 by 250swb

[AnakChan]

Cheers for your response. So it's nothing bubbling underneath the surface. It's on the surface (but possibly quite "embedded" into the top as rubbing with isopropyl hasn't helped). It does live in the Leica full leather case with felt in the inside. So my thinking is due to moisture that resulted in fungal growth - assuming it is fungus.

I'll give the hydrogen peroxide/ammonia a shot and see if I can get UV light to kill it. I just hope whatever I use doesn't remove the black lettering too.

[AndreasG]

vor 15 Minuten schrieb AnakChan:

I just hope whatever I use doesn't remove the black lettering too.

It is easy to repaint the black lettering, fill with black paint from Tamiya or Revell, let it dry a little and remove the excess paint with a cloth and little thinner.

[nitroplait]

My guess is the culprit of the corrosion is likely the chemicals in the leather.

I have a recent encounter with not dissimilar Leica corrosion problem.

I'd advise you to stop using the case. The problem will not disappear with UV light.

You don't happen to use a Leica case type 14870?

See post #50 for my conclusion:

 

[AnakChan]

@nitroplait argh, yes that is the case I've been using. That is a very interesting to suspect the case. I just assumed it was humidity and fungus from the case but didn't consider chemicals.

I take it no way of cleaning it?

[250swb]

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50 minutes ago, nitroplait said:

 

I'd advise you to stop using the case. The problem will not disappear with UV light.

 

UV light not make fungus disappear, it will kill the fungus, you still need to remove it.

[jaapv]

Silver polish?

[250swb]

4 hours ago, jaapv said:

Silver polish?

I'm not sure that would work, isn't there the possibility of giving the top plate an uneven high shine, like the edges of a well worn satin chrome body or the scuffs caused by a Leicameter?

[jaapv]

I doubt that it would impart a polish. Chrome is much more hard than Silver. I think this is a quite resilient residue which does need a mild abrasive. But one must try it out on a small unobtrusive spot, I agree. There are no guarantees. 

[AnakChan]

I have been trying with a polishing leather cloth so far and those spots are pretty stubborn. So I guess if I want to get rid of it, I do need a mild abrasive as mentioned, but I do fear that it'll remove that satin look too.

[dem331]

I had some stubborn finger stains on my piano keyboard.  I suspect that one of my daughters had some cosmetic remains on her fingers when playing.  I went to a piano dealer and he recommended Würth P10, a car polishing product. He told me they use it for the keyboards and bodies of all their pianos. It removed my stains with minimal effort

Maybe try this, or write to Leica to see if they recommend anything. 

[250swb]

11 hours ago, AnakChan said:

I have been trying with a polishing leather cloth so far and those spots are pretty stubborn. So I guess if I want to get rid of it, I do need a mild abrasive as mentioned, but I do fear that it'll remove that satin look too.

I don't think it's an abrasive that you need or want. Try vinegar, or silverware tarnish remover (silver dip), or WD40 applied on a cloth. You need to find something to dissolve the black marks, not scrub them off and potentially cause damage. 

[AndreasG]

First I would try with water and soap.

[Mute-on]

Looks like verdigris. I had something similar on an MP kept in a canvas bag against a cold internal wall. It wiped off with a baby wipe or similar IIRC. Hasn’t returned. 
I would avoid anything remotely abrasive or corrosive. It shouldn’t be necessary. Warm water on a cloth, rung out to be damp for a start. An alcohol wipe would be as far as I would go. Just avoid rubbing over the engraving directly. 

Edited December 29, 2023 by Mute-on

[AnakChan]

I've attempted to clean with isopropyl alcohol, and with a polishing cloth and have to say I was somewhat skeptical of using just soap & water but it has cleaned up most of the spread/black stains from the polishing cloth that's left behind and it looks better. Those stubborn black spots remain (I don't know if they're pitted or just surface) but at least the larger broader dark/grey patches are less grey. Will continue trying to see how I can get rid of the black spots themselves. But definitely they're not going back into that Leica case.

[Pyrogallol]

My Leica repair man, 40 years with Leitz, says that leather is the worst thing to keep cameras and lenses in because of all the natural organisms that live in it.

[pgk]

Using a cotton bud you could try dliute ammonia or bleach and see if that helps. As with any chemicals, they need to be kept away from seals and any other area where they might cause damage.

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Hallo,

Look here: Leica M

[oldwino]

You could also try 3% hydrogen peroxide.