solder stain

clarke

Registered User
Oct 25, 2009
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Hello,
The stains are "growing" from what appears to be the solder points on the interior dial.
They probably can't be eliminated but can anyone suggest how to keep them from spreading more?
thanks.
c.
 

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laprade

Registered User
ckarke,

It looks as if the contamination is from the metal backing behind the paper, (it is paper?). If the stains are getting bigger since you got the clock, then something is reactivating the "flux" used in the soldering. Such as kitchen humidity.

If the stains were already there when you got the clock and haven't got bigger, then it is possible that they were caused soon after the soldering.

I don't think the solder itself would cause the problem, but fluxes can be very unstable and corrosive.
 

Jeremy Woodoff

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Jun 30, 2002
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If the stains are being caused by acidic flux, maybe you can neutralize it by applying a paste of baking soda and water to the area around the solder on the back. You might also try a de-acidification spray on the dial as a whole. I cannot guarantee that applying the baking soda will not cause a different problem and make matters worse, but if the spots are growing, it may be worth a try.
 

Thyme

Banned
Sep 18, 2006
3,948
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metro NY area
ckarke,

It looks as if the contamination is from the metal backing behind the paper, (it is paper?). If the stains are getting bigger since you got the clock, then something is reactivating the "flux" used in the soldering. Such as kitchen humidity.

If the stains were already there when you got the clock and haven't got bigger, then it is possible that they were caused soon after the soldering.

I don't think the solder itself would cause the problem, but fluxes can be very unstable and corrosive.
I agree - your observations are most likely correct. Probably someone soldered it with acid core solder. There is no way to rectify the corrosion damage that afflicted the paper dial. If it is worsening, the best you can do is disassemble it, clean it all off and re-solder it with resin core solder or resin flux. (And if the new solder doesn't want to adhere, you might realize why someone used acid core, perhaps out of desperation.)

Rosin core solder is not corrosive; acid core is, very much so, as the name implies.
 

laprade

Registered User
If you speak to a restorer of etchings and prints, they might be able to help. The corrosion on your dial could be a very severe form of what print people call "foxing".

The problem with the staining is that it looks to be mineral as opposed to organic. If it was organic, then hydrogen peroxide could remedy the problem.
 

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