mixing scrap gold

As a rule, you can mix one 14 k yellow with other 14 k yellows (assuming they are not contaminated with lead ) and wind up with a workable 14k alloy.

You can mix 14 k yellow with 14k red and/or 14 k green gold and wind up with a workable 14k alloy.

With the careful application of mathematics, you can mix 10 k yellow with 18 k yellow and wind up with a workable 14k alloy

Do not mix white with yellow, in fact, I suggest you avoid melting white gold altogether. The stuff is a pain in the butt.

Do not mix dental alloys with jewelry alloys.

At any point, you may end up with an alloy that is completely unworkable, for reasons not apparantly obvious, but that is the exciting part of remelting.

Paul K. Dickman

What is your purpose? I can help with gold, having refined it for years, but I need more input than that.

Harold

Hey Harold, I have an ounce or two of dental gold...what do you think it is and what should I do with it?

Put it in with those brushes you never sent to me and I'll dispose of it for you. :-) I've really enjoyed not using them.

(Depends on the alloy in question. Dental can be quite good from a scrap perspective. Typically contains some of the platinum group, although when you sell it you're highly unlikely to be paid for the Pt. group content. Gold content can vary wildly, but it's the best gold scrap on the market).

Remember, the ounce in this case weights 480 grains, not 437.5.

Harold

having started to collect gold coins i have also started to collect little gold bars. i think it would be very interesting to be able to produce my own out of scrap gold. i do not know how to go about sorting it out but have an idea that mixing alloys with different metals to produce different colours does not sound a very good idea. where can i get a small furnace?

That, of course, would yield a bar of unknown quality. Gold jewelry is not always just cast, nor are all bench men ethical. One of my customers was quite proud of himself when he told me that he typically under karated when alloying his gold. Strange, eh? "Hey, I'm dishonest, and I'm proud of myself".

. i do not know how to go about sorting it out but have an

Jewelry is often made in pieces and assembled by soldering. The joints, when properly done, are not visible, but the solder is yet another contamination with which you would be dealing (yes, it contains gold as well). You are also inclined to find white and yellow or red gold combined, and mixing them isn't a great idea. Yellow gold contains silver, which does not alloy well with nickel, which is generally contained in white gold. Believe it or not, when you combine silver and gold, you get green gold.

It would depend on your objective, of course. If you wanted to cast bars to send to a major refiner to avoid any question about the whole of the gold content, it might not be a bad idea. A well blended heat, cast into an ingot, then assayed, would be a reasonable concept, but if you want something that is pretty to admire, you're likely to be quite unhappy. Gold, in a pure form, is beautiful, but once alloyed, the beauty fades quite quickly. Gold that has been alloyed for jewelry has at least one element that will oxidize when heated--even white gold (typically nickel), so when you melt the gold and cast an ingot, it won't be pretty, but most likely covered with oxides. Pickling will restore a clean color, but it won't be shiny. Pure gold, on the other hand, will come out shiny, although it may show a crystalline structure, and almost always pulls a deep pipe as it contracts. That's a sign of pure gold, and it tends to go away with very little contamination. A casting that is frosty looking, even when yellow, is a sure sign that the gold isn't pure.

There's nothing preventing you from building a small one, but unless you intend to melt large volumes, you don't really need one. Jewelry supply houses sell Hoke type torches and all kinds of small melting dished, some even with attachable handles. You can melt as much as ten troy ounces with such a setup, and it's faster and easier than a furnace. If you're still hell bent on a furnace, I can suggest a simple design that works quite well, and could be built for less than $100, assuming you have a few tools to work with and have some common sense. I don't mean that in a cruel way, but not everyone works with their hands. Just wanted to have you understand that it requires a little skill. Again, a good jewelry supply house should be able to sell you a small furnace, too. There's even a couple companies that make an electric model that you pick up and pour, one of which is a Handymelt, as I recall. Kerr makes one, too. Both use a straight sided crucible machined from graphite. Crucible life is short, and they're expensive.

If you have access to a few chemicals and have an interest in refining, I could also provide some simple instructions, but be aware that this is best done with a fume hood, and should not be done where children can access the project. You work with nitric, hydrochloric and sulfuric acids. You'd have to invest in some lab ware and other things to do this, it isn't cheap.

Let me know.

Harold

Harold, have you ever electrolytically refined gold? Would you consider this method practical on a small (home workshop) scale? My intention would be to remelt the refined product, the combine it in controlled alloys for jewellery fabrication.

(I've got lots of dirty gold, too - just like the OP)

-- Jeff R.

thanks for the advice. i am going to the local college to see about a jewellry course that starts after christmas.

Jeff, At some point in my refining career I did consider it. I went to the trouble to build the gold cell and the anode molds, but I never ran it. It had titanium buss bars (inert) mounted on a polypropylene plate, which sat atop a cell made from fiber glass. It would have been heated with a quartz heater controlled with a thermostat.

I had evolved into the process of refining my gold a second time, in large batches, which consistently yielded quality above industry standards, (.better than .9995) so I just stayed the course. My objective, at first, was just for pleasure, but when my hobby became a full time job, I sort of lost interest in the experimental state of my learning process and stayed with that which yielded great results and was fast. I was so busy that I worked seven days/week and long hours. Rarely less than 14. What was a hobby turned into a great business, but it was not planned.

A gold cell is not suited to refining gold that isn't already quite fine, especially if the contaminant is silver. The chloride solution stops the process by building a sheet of sliver chloride over the anode. That condition can be overcome to some degree by superimposing an AC current over the DC current, but I never explored that, due in part to never running the cell. Beyond that, if the electrolyte gets contaminated by excessive dissolved base metals of any kind ( copper, zinc and nickel are to be expected), you end up with mechanical inclusions, so the gold quality is not what you'd expect. You also must have a considerable amount of gold tied up in electrolyte, something like two ounces/liter, as I recall. It's not really a great way to go on a small scale, and not necessary if your objective is clean gold for jewelry. Chemical refining is what you should entertain, although you must have an adequate facility (fume hood and working space that resists acid and acid spills). That would be true if you ran a gold cell, too, for you have to prepare your electrolyte, and the cell yields hydrochloric fumes.

If you want to contact me on the side, I'll send you a pic (128 kb) of the gold shot I turned out. Very impressive, and a good standard by which you can judge refined gold that you may turn out. At first it may not be as good as it is when you become more familiar with the process. A lot about the quality of gold is apparent in its appearance once you become familiar with it. I'm willing to provide guidance if you'd like.

Harold

That will be a great way to get your feet on the ground----and understand more about the metals involved. Good luck with the class----should be fun and informative for you .

Harold

ironically my uncle did the same thing thirty years ago, my dad says. must be some thing in the blood. or the fact that i come from a steel city, sheffield uk. sheffield is also good at silver plating.

Whoa! Scratch that idea then. I had naively thought that this method would be somewhat simpler -and- less toxic than that. The killer, though, is the 2 oz/litre invested in electrolyte. Sigh... outa my league.

Thanks for the benefit of experience, Harold. It was really a whacky notion, anyway.

-- Jeff R.