any experience out there with melting gold? I have a problem!

[joncooper1986]

Hi folks, so here's the problem.
I was melting down some scrap gold in a crucible...I pored myself an ingot, and there must have been some molten gold that didn't come out of the crucible. I found this out because after I made a silver ingot and noticed that there was a substantial amount of gold blobs in the silver ingot. Is it normal to not have all the molten metal come out of the crucible at once? As for separating the gold from the silver in the poured ingot, I am considering heating it molten and simply letting it cool in the crucible. My theory is that the gold (being twice as heavy) will stay at the bottom and then i can separate the two by cutting them apart at the seam. Any thoughts?

 

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[KevinInColorado]

When remelting, the two metals will instead form an alloy. A traditional way to separate them is to:
1. Melt the material
2. Dribble the molten metal into water making "corn flakes"
3. Put the flakes into acid (look up which acid yourself so you see the safety rules)
4. Remove the resulting solid gold pieces
5. Put copper into the acid to precipitate the silver, filter out silver powder
6. Put iron in to precipitate the copper, filter out copper powder
Neutralize acid and dump rusty water down the drain.

 

[rlbaker]

Did production casting for the industry for 25 years and I'm afraid you are out of luck trying to separate your blend of silver and gold. Next time you do a pour make sure you not only do a lot of swirling after you add your last bit of flux to clear any "crud" off the melt but that you poke and stir well with a graphite stirring rod, it is easy to have a not quite liquid spot in the bottom of the crucible. Good luck.

 

[KevinInColorado]

Mr Baker is right about how easy it is to have a partial melt. Happily he can now learn how to separate the two metals via my post. And yes, I have seen this done successfully!

 

[GoldpannerDave]

When remelting, the two metals will instead form an alloy. A traditional way to separate them is to:
1. Melt the material
2. Dribble the molten metal into water making "corn flakes"
3. Put the flakes into acid (look up which acid yourself so you see the safety rules)
4. Remove the resulting solid gold pieces
5. Put copper into the acid to precipitate the silver, filter out silver powder
6. Put iron in to precipitate the copper, filter out copper powder
Neutralize acid and dump rusty water down the drain.

Yep, simple applied chemistry. Love the simple approach.

 

[joncooper1986]

Thanks guys. I think I will do just that- disolve the silver from the gold with an appropriate acid. I am somewhat surprised to learn that once in liquid state and assuming I allowed the material to solidify in a crucible, that the gold wouldnt naturally rest on the bottom seeing as it it twice the density of gold. Is this because the molecular structure will have changed to create a compound/alloy? I only ask because in the ingots i poured it appears that the gold and silver kind of stayed blotchy and didnt mix together.

 

[Jimmydolittle]

Kevin is right, I used to refine gold from computer scrap. I didn't go after the silver though, but I know the procedure.

Yep, simple applied chemistry. Love the simple approach.

 

[Hoser John]

If you use borax glass and saltpeter when you process you get a much cleaner product,enrich the kt and no other chemicals needed. Just a simple scratch test to determine the purity and sold-John

 

[Bonaro]

The gold silver blotchy thing could be due to having a cold spot in the mix as the melting points of the two metals are different

 

[scoy]

I have a lot of experience melting Gold and Silver. The metal will alloy , it will not density separate. Metal can get stuck in the crucible if the crucible is old and seen alot of use a ring can be etched into the the inside of the crucible due to flux erosion that occurs in the zone between the flux and molten metal. I have melted 1000's of of troy oz's of both Silver and Gold. However you can also have metal retained in the crucible if you did not flux the melt it may be dirty and it froze up while pouring.