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Old 14th Apr 2012, 5:45 pm   #1
Join Date: Dec 2008
Location: Wincanton, Somerset, UK.
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Default Silver dip: what's the secret?

I've recently "restored" some rather grotty-looking (silver plated) BNC's with a very old jar of Goddard's Silver Dip. This dip really does work, and even cleans the centre-pins.
Now, I seem to remember once reading that this solution reduces the silver (sulphide) back to silver, so you weren't actually losing any silver in the process. However, the instructions on the jar (which must be 20+ years old) state that you should not leave objects in the solution for more than 5 minutes or so: which might be interpreted as a surface removal process?

Does anyone happen to know the chemistry involved?


NB A a small deposit of colourless crystals has formed in the bottom of this jar.
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Old 17th Apr 2012, 2:07 pm   #2
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Default Re: Silver dip: what's the secret?

I know that I did a really good job of cleaning some silver plated roller inductors with the same silver cleaner. They looked really fantastic but I could not get them to work as the cleaner had put some sort of coating on them and although they looked good, there was a lot of problems with the electrical contact between the rollers and the coil windings. I had to re-clean them with a soft grade of plastic scouring pad to get them to work again. I used the same sort of pad used to clean "Teflon" tm. cookware.
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Old 17th Apr 2012, 3:31 pm   #3
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Default Re: Silver dip: what's the secret?

The silver cleaning action is by thiourea in sulphuric acid.
It dissolves the black sliver sulphide, and the acid will eventually dissolve everything else given long enough. You end up with less silver than you started with.

I think they now add something to coat the surface to resist further tarnishing, hence the problem mentioned above.
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Old 17th Apr 2012, 5:25 pm   #4
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Default Re: Silver dip: what's the secret?

I did the same thing with some BNC connectors that had gone black with tarnish, works a treat. Would not leave anything in the solution for long however, I think it must remove more than just the tarnish.
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Old 18th Apr 2012, 8:11 am   #5
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Default Re: Silver dip: what's the secret?

When I am 'recycling' old BNC and N connectors, I just dismantle them and leave them in some Coca Cola overnight. A quick scrub in the sink with a nailbrush, let them dry and they are like new!
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Old 18th Apr 2012, 11:18 am   #6
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Default Re: Silver dip: what's the secret?

Back in the 1970's, when there was a Worldwide shortage of 74H series IC's, the component jobbing company I worked for bought up 1000's 'out of date' (tarnished pins) stock we could find.

Even so, buying & QA departments wouldn't touch tarnished product with a barge pole so, we resorted to dunking the tarnished product into washing-up bowls filled with Goddards Silver-Dip and then rinsed them in warm water and they came up looking brand new and we barely met the supply demand & could charge 5 -10x the pre-shortage prices.

We made a fortune during that period !
When I die, please don't let my Wife sell my collection for the amount I told her I paid for it!
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