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Question: I found a great source for used gold. Right now I can get mixed karats and some solder well below spot. I want to take advantage of this deal but I’m not sure what to do with it. I know I shouldn’t cast with this kind of metal. Is there a gold refining method that will let me use this material? If I melted it all, I would end up with something like 12.5 karats. This can be raised to 14 karats by adding purer gold. I don’t have the formula to do this, however. How can I figure this out? Also, if anyone has any gold refining advice or any tricks for reformulating gold I’d love to hear them.
By International Gem Society 2 minute read
gold solder strips

These gold solder strips contain gold as well as silver, copper, and zinc. Photo by Mauro Cateb. Licensed under CC By 2.0.

Answer: Not recommended! Reformulating alloyed gold with pure gold can lead to unpredictable results. Before you melt down gold for jewelry making, carefully consider your options.

The Problem with Refining Alloys

Even if you raise the quality of your bargain mixed-karat gold by adding the appropriate amount of pure gold, you never know what could be in the alloy. Traces of unwanted elements can make the gold brittle and affect the color. The gold may also cast badly. Generally speaking, you will screw up your material in unpredictable ways. When gold is re-melted into new jewelry with no regard for metallurgy, the pieces can just disintegrate. I’ve seen this happen.

Gold Refining Options

You have two options for gold refining. Refine it yourself or have someone do it for you. Of course, if someone refines it for you, your bargain may turn out to be not such a bargain after all. You will need to do a detailed costing to see if it’s still viable. There are several gold refining methods you can try for yourself. Some DIY gold refining systems are available.

Personally, I have refined gold by dissolving it in aqua regia and re-precipitating it on copper. You need to know a little chemistry for this procedure. There are electrolytic methods, although these need cyanide.

You’ll need to choose the gold refining technique that best fits your facilities, training, and circumstances.

Dr. Clive Washington

broken gold ring

Broken two-tone gold ring. Photo by slgckgc. Licensed under CC By 2.0.