Question
Two gold molds
Hello,
I collected some 18k gold jewelry over many years, and decided to try to melt it on my own (sort of a possible hobby). In any case, I used a melting furnace and poured (sort of gunky consistency) into a couple small graphite molds. My question is, the gold has a blackish/gray coating on it; I'm guessing its from the graphite crucible that it was melted in - how do I get that stuff off?
History on the melting machine. I had to order the 110 volt machine, and I know the temp "should have" reached 1063 degrees Centigrade for a proper melt. But the machine would only reach 1003 to 1015 degrees. In contacting the manufacturer of the machine, they claim that only their 220 v machines will reach 1063 degrees (albeit, that is no where in their ads) - but of course this does make sense.
Okay, anyway; the 18k gold did melt; but cooled during pouring very quickly - coming out very well for the first two seconds then taking on a putty type pour. The molds obviously aren't pretty - they're "rocky" looking on top and sides. I'm not concerned with that, as I just want to gift them to my adult children, BUT they look terrible with all the black/gray coating. Can you help? I'm attaching a pic of both - one top side, and one bottom side. Thank you so much. Jack
AnswerJack there are a couple of ways to achieve what you want.
I think the best one is to buy some sparex pickle solution and use an old crock pot to pickle the piece. It might take some time but it should remove the tarnish. Be sure and use wood or copper tweezers to remove your gold from the pickle, and be sure to rinse it off well.
You could sand the surface and polish but I don't recommend it. it would decrease your gold weight.
Or you could remelt the gold and use more borax on the top when you melt and pour, then pickle to remove the borax. Again not the best solution because it burns off the metal but it should raise the Karat, but it also makes it more brittle, unless you replace some of the alloy you burn off.
I never liked the electric melting furnaces, I preferred oxy-acetylene torch. It is much quicker and cleaner.
I hope this helps.
Chris
