I processed a couple thousand pins that were gold plated the full length. When I got to the cupeling part it seemed that the base metals were oxidizing nicely and getting absorbed. Eventually, my button was soft, dense, and 'rose gold' in color. Did this mean there was just some copper left to go? The 'baser' base metals leave first, right? Well, fresh bone ash cupel and back into the furnace. I don't know if I turned the propane up too high, left it too long, or what, but that cupel was fully spent and also empty. What happened?
How hot does a cupel furnace need to be? Can it get hot enough that PMs are oxidized into bone ash cupels?
- Thread starter zamistroe
- Start date
Help Support Gold Refining Forum:
I have two questions here.
Why did you select cupelling when you have a Copper rich material?
How much in weight was these pins and what kind of pins?
Generally copper rich materials benefit from scorification in assay quantities or in production quantities some form of parting to dissolve away the copper selectively.
My understanding was all the non PM would oxidize and leave just Au and the like. Not so?
I had 12 oz of the sort found in Amphenol connectors. They were new old stock, just bare pins in a bag.
Ok, caused by too much time, heat, or something else? What process is used for retrieval?
I've not heard of Bugbee. Thanks, I'll check into it.
I should also mention, I added lead to the the button before the final firing. About an equal weight. But that's not scorification I guess. I'm not clear on the difference between scorification and cupelling.
Scorification takes place in an open shallow ceramic dish and uses granulated lead and your material and borax. The lead oxidizes base metals into a slag and when the volume of the lead after it is driven by oxidation is about half, the remaining lead and slag is poured into a assay cone mold, deslagged, and that lead alloy chunk is cupelled in a bone ash cupel.
This is an assay scale procedure not for large lots.
This is an assay scale procedure not for large lots.
Last edited:
I'm a metric guy but that is like 336 grams?
That could get between 0.2 and 1.5 grams ish depending on plating thickness.
How did you treat them prior to cupelling?
Copper seem to make cupelling harder so I wonder why you chose cupelling?
Best approach would be Cupric Chloride etching aka the AP process.
This will give you clean Gold foils which can be refined or melted as is.
Edited to adjust numbers.
Last edited:
Sounds about right.
I didn't know that copper makes cupeling difficult. I thought all the base metal was supposed to oxidize and absorb and the PM wouldn't. Fire is preferable over acid to me, but if I have to then I have to.
What are your thoughts about getting the PMs that seem to have been 'dragged' into the cupel back out? Melt in a crucible with flux? (borax/lye?) Or a different acid/chemistry process?
There might be so little it might be hard to get it out.
You could try to grind/ crush it fine and find a good flux and attempt to smelt it or scorify it.
Edited for spelling
Last edited:
With so much more copper to get rid of for such a small quantity of gold your use of lead for scorification releases a lot of lead to the atmosphere as the lead will volatilize in the process. Scorification is typically an assay process and to process 330 grams of material will require burning off a lot of lead. And then when you are done you will have to purify the gold you recover. I know looking at 330 grams of plated gold may look like you are dealing with a lot of gold but in reality, it is a thin surface film and no where as rich as it looks. This is unquestionably a process for AP for a hobby scale refine.
