Just curious as to what causes this kind of color on my button? Is it an oxidation thing or what? There was nothing like that when I poured it into a bar, only when I leave it to form a button. I tried cleaning it off in a water and sulfuric acid boil but that didn't do anything. The bottom of the button is fine, its just the top that's discolored. :?
What Causes this Color?
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Sometimes if you re-melt and you use lots of Borax the Borax pulls out the Copper. Or at least enough of it to make the difference that you see.
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Maybe the glaze on the crucible was enough?
Just thinking out loud, but when you pour a bar it is likely to cool more quickly. When you leave a button in the melting dish, there is more heat retained in the dish itself, so the button will cool a little more slowly, which can allow the base metals to oxidize a little more. Of course, that assumes that everything else is exactly the same. Perhaps this button was a bit more contaminated than your previous pour into a bar. I don't know. Just giving you some food for thought.
In any event, it shows that the gold is a little contaminated, both by the oxidation on the surface and the lack of a pipe. You can use it to deNOx solutions in the future as Harold did.
Dave
In any event, it shows that the gold is a little contaminated, both by the oxidation on the surface and the lack of a pipe. You can use it to deNOx solutions in the future as Harold did.
Dave
My guess, copper oxides. When you pour it into a graphite mold it both cools faster and there might be some carbon dioxide created that formed a bit of a protective atmosphere. Leaving it to air-cool takes longer and the air have time to form an oxidized surface.
It's almost a spitting image of my 26 g button, made from source material that only registered as gold and copper on an XRF and left in the melting dish to cool down.
Not cleaned since I picked it up from the melting dish. The top side is more dull and have a red tone to it.
Some white borax is stuck on the right side seen from the bottom.
I think in my case, the fact that the borax isn't discolored points to quite low level of contaminant.
Göran
It's almost a spitting image of my 26 g button, made from source material that only registered as gold and copper on an XRF and left in the melting dish to cool down.
Not cleaned since I picked it up from the melting dish. The top side is more dull and have a red tone to it.
Some white borax is stuck on the right side seen from the bottom.
I think in my case, the fact that the borax isn't discolored points to quite low level of contaminant.
Göran
I only did an xrf on the precursor material and it was 2 parts gold and 1 part copper.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=60&t=27282&p=295768#p295768
From that picture I think it went through at least three baths of boiling aqua regia, filtering and precipitation. Each time coming back to that clay-like substance. In the end I managed to clean it up using several boiling ammonia baths for a day and still got that contaminated button. But my thought was that whatever survived the wash procedure would probably burn off if I melted it. Another re-refining and it should be perfect.
Göran
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=60&t=27282&p=295768#p295768
From that picture I think it went through at least three baths of boiling aqua regia, filtering and precipitation. Each time coming back to that clay-like substance. In the end I managed to clean it up using several boiling ammonia baths for a day and still got that contaminated button. But my thought was that whatever survived the wash procedure would probably burn off if I melted it. Another re-refining and it should be perfect.
Göran
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Woah you got THAT from "the white stuff?"
anachronism said:
Yeah, that was the white clay I put in your trash bag for half a day while I was chasing a barren solution. :lol:
Göran
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Yeah I see what you mean about "thank heavens for the XRF" now. :lol: :lol:
You may assume, but you never know where your gold is if you don't test.
I want an XRF too, but I can't afford one for the moment.
Göran
I want an XRF too, but I can't afford one for the moment.
Göran
