# Refining silver brazing wire



## qst42know (Sep 27, 2008)

I have about 3lb. of assorted grades of silver solder, wire and sheet. Some industrial based on it's hardness and off silver color, and some jewelers silver solder based on it's low melt temp and good color match to sterling. None are identified for alloy type.
I will keep some of each for my own repair work and other assorted projects, however it is way more than I will ever need.
What would be the most efficient chemical process to refine this saleable purity? Silver cell or acid?


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## Harold_V (Sep 27, 2008)

Acid.. Dissolve with dilute nitric, then recover with copper. The end product will still need to be parted in a silver cell for decent purity. 

If you choose to part in a silver cell at the outset, you will encounter problems.. As the copper level increases in the electrolyte, you will co-deposit copper with the silver, and it's entirely possible that you will have difficulties with the anode liberating the silver because the copper content is too high. 

I ran my silver cell for years, starting with no copper in the electrolyte whatsoever. It's not a requirement for refining, but does increase conductivity, from all indications. Silver that is first plated without copper in the electrolyte will deposit heavily, adhering fairly tightly to the cathode, and the nodules of crystal that develop are somewhat more substantial than those that come from an electrolyte that contains some copper. They are much easier knocked down when copper is present---so you be the judge if you think you want to start with copper, or not. In my case, I extended the useful life of my electrolyte by not adding any. It accumulated more than fast enough by the residual copper that is difficult to eliminate from silver that is cemented from solution using copper. 

You might consider that the solder you possess is worth far more than the silver it contains. If you're looking to recover values, it might be in your best interest to sell the solder to someone that can use it, and buy silver in it's place. 

For the record, I have processed literally hundreds of troy ounces of silver solder, although it was years ago, when I was actively refining. I withheld a fair amount, which I kept as partial payment for my refining fee. Makes it much easier to use silver solder when required instead of paying to buy your needs. 

Hope some of this helps. 

Harold


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## qst42know (Sep 27, 2008)

Harold

Though I brazed for a living for about 5 years and consider myself a fair judge of silver content by how it behaves in use, this material came from a wide variety auctions, and estate sales, etc.. I suspect these mystery alloys may be a tough sell as they are.
I do collect many silver electrical contacts as well, the best of which come from switches and relays rated 25 amps or better. I may need a silver cell anyway. 
Having never run a silver cell myself, should I expect significant fumes from one? 
And should I wait until I've constructed a fume hood for myself? 

Thanks. Chris


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## Harold_V (Sep 28, 2008)

Once a cell is in operation, it yields no fumes, although, because it runs at a warm temperature, it does evaporate water. 

You'll create fumes when you make your electrolyte---but you may have success doing that out of doors. I always had a fume hood, so I wasn't troubled with the fumes. 

I understand about the varied types of solder you may have. I was fortunate in that many of the rolls I received for refining still had tags hanging from them. The big concern, as you would know, is if any of them contain cadmium. 

Contacts can be interesting. Many are made from tungsten, but they're fairly easy to identify if they've been removed from the buss. The back side has a waffle pattern, which I didn't find on any other types of contacts. They yield less than 50% silver due to the specific gravity of tungsten, but well worth processing. You can leach them with heated dilute nitric acid until they are barren of silver, at which time they will break easily. When they break, if there's a line in the center, that's where some silver still remains. I used to boil them for an extended period of time, until the thickest contact would break easily. That way I was assured I had recovered all of the silver. 

I found some of the light duty silver contacts to contain something other than silver. I had no means to identify the material, but I always wondered if it might be cadmium. Should you get a light yield from a batch, that may be why. 

Hope some of this helps.

Harold


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## Anonymous (Sep 28, 2008)

Dang Harold, I was about to ask the very same question that qst42know has asked. So your reply was just what I needed. For me you knocked one out of the park. I have about 20 lbs to deal with. Thanks again


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## Harold_V (Sep 28, 2008)

Even a blind squirrel finds the occasional nut! 

Glad to hear you found something useful in my comments, looker.


Harold


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