Crucible borax/carbon dilemma trapping gold

Never had this problem before. Triple processed in AR filtered and put complete filter w clean gold into small crucible, added Borax to keep it from flying off and this is the only time I’ve had this problem. I have used two cans of Map on it and it glows bright orange/yellow, gold is melting but the remnants of the filter seem to be pure carbon at this point and I can’t get burn it off. Any ideas? I’m down to one good map torch head but it should still be plenty for 7 grams of gold. Here’s detailed pics. I tried separating it and putting pieces into another crucible. Help!

I would place the dish in a beaker, add some battery acid, (35%) sulphuric acid), and apply some heat. That should dissolve the borax and free the gold.

Take care!
Phil

That's an obscenely large amount of borax. Way too much.

Also if your borax goes that colour, then your gold isn't as pure as you thought. Triple refined in AR that dish should be pink. Clean gold melts together and pools whereas that seems to not be behaving.

Also judging by the state of the prongs holding the dish it's entirely possible that you're having iron flakes going into your melt, but that's as an aside. It happened to me once and I'm anal about that now.

I'd put the whole thing in dilute H2SO4 warm it, dissolve off the borax and start again. Thanks for sharing though, and good luck.

Break it up, remelt the borax/gold in little pieces instead of all that. Less heat required.

And get a real torch.


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Well this got interesting. Took first suggestion and went the sulphuric acid route w high heat. After three hours nothing. So decided to go the poor man’s nitric route and started adding nitrate powder. Lots of red fumes but it’s still doing nothing. I killed the heat and it’s been a few hours and it’s now like frozen water but in a fiber sort of way. Feels like it’s mostly frozen but it’s in the mid 40’s.

Did you add Nitrate to the Sulphuric solution?

Are your gold beads at the bottom of that mass of borax?

Yes, added to the sulphuric. I’ve used nitric to remove last bits of borax from gold buttons so figured it might help. The gold is trapped throughout the chunks of the “glass blobs” in small balls. The gold on the outside and not trapped pulled together and I was able to remove. It did destroy the crucible but not doing a thing to the glass. Might have to go the hammer route and smash everything up inside a double layered thick plastic to get it to separate from the crucible in smaller chunks then melt individually. I wish there was a process to completely just dissolve the Borax but I have no lab strength nitric on hand.

I wish there was a process to completely just dissolve the Borax but I have no lab strength nitric on hand.

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There is... diluted sulphuric acid! I use some distilled water and 35% sulphuric acid. It works every time!
Now, if you evaporate too much water, then the borax will "coagulate" as the solution cools; and if too dry, it will become hard as a rock!
When that first happened to me, I added warm water and fresh sulphuric… applied some heat until it was fluid. I allowed the solids to settle, and decanted. Repeat until the gold is free. The trick is don't let the solution get cold!
Remember, the borax is dissolved in the solution, it doesn't "vanish".

Take care!
Phil

Thank you great idea. I’ll give it a shot

anachronism said:

Also if your borax goes that colour, then your gold isn't as pure as you thought. Triple refined in AR that dish should be pink. Clean gold melts together and pools whereas that seems to not be behaving.

Also judging by the state of the prongs holding the dish it's entirely possible that you're having iron flakes going into your melt, but that's as an aside. It happened to me once and I'm anal about that now.

Click to expand...

Per the underlined - Jon is quite right (on both accounts) The black color of you borax slag is "not" carbon as a result of the filter not completely burning up --- rather its the result of iron (oxide) slagging off during the melt


so - ether your gold was not clean & had iron in it - or you are getting the prong of your tongs holding the dish to hot causing the iron to oxidize & slag off - or a combination of the two


it's also why (at least in part) why your gold did not come together in a pool of molten gold --- The other part of that (as Jon said) it using to much borax for the amount of gold you are melting

Borax is a very "thick" flux/slag so if you have to much borax for the amount of gold your melting - the gold will not come together in a nice pool

Kurt