Cupelling help

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ben2363

Active member
Joined
May 23, 2019
Messages
26
Hi all very new to all this.
I tried my first go a cupelling, and it did nothing at all.
It started to melt but after 40mins it didnt do a thing. I had furnace at around 950 to 1050.

One thing I didnt do was pre heat the cupels
Is this a must? And for how long if it needs to be done.

Ben
 
°C.
I smelter down gold/silver cons. The sample was full of gelena so I didnt add and lead to it.

300grams of cons.
900 g of soda
300 silica
200 borax
And a iron rod.

After the pour I had a 118gram button

I cut button up and placed in to 4, 7a cupels.

Had in furnace for about 45min and nothing at all

Ben
 
It’s hard to say how much of the lead sulfide you reduced in your smelt with iron. A #7a cupel only holds about 40 grams which is why, I suppose, you broke the the 118 gram button into 4 pieces.

I would carefully weigh a few grams, 2 maximum, and wrap the sample in 10 times it’s weight of lead and cupel it normally. The resulting bead will be all Precious metal. From this test you will know the percentage of PM’s in your sample. From there you can adjust the sample to lead ratio until you get the best recovery.
 
Thank you. So rule of thumb is 10x the weight??
2 you grams on sample then 20grams lead??
 
That is just a starting point. Are the cons high in Silver? If so you can likely part the resulting bead in diluted nitric acid to determine the gold content. If the gold is more concentrated than the Silver you will need to add Silver before cupelling to be able to determine the gold by parting.
 
20220903_165235.jpg
Not sure what's going on here.
I put 2grams of the lead/con button with 30 grams lead.

Both were in for 1 hr and 45mins at 950 °C

Any one have any ideas?

Thanks
 
One (or more) of a few things:
Too much metal for your cupel.
Cupel wasn't hot enough and froze (the second picture does not look like the cupel took up much lead)
Too many base metals, need scorification or more appropriate fusion smelt
 
Was the sample wrapped in lead or just placed on top of it? A 7a cupel should hold the 30 grams of lead but you would see from the side of the cupel if it has been fully absorbed, which in this case it wasn't. Are you providing airflow in the furnace to drive the lead?

I would try more heat, like 1050ºC the other option is scorification as snowman suggested.
 
Thanks heap. I dont have any scorifictions dishes I'll have to buy some.

That material is now stuck in the cupels so I'll have to brake it up.

I have air flow going the lead was molten the whole time but it just didnt absorb.

Should I re smelt the 118 grams again adding more soda and start from scratch?
 
Is that slag on top of your Lead? I don't know if you know to remove all slag, prior to cupellation. Otherwise the Oxygen cannot get to the lead. I would try reheating what you have, pour into a small preheated conical assay mold, let cool, hammer all slag away, then try cupeling with a fresh hunk o Lead.
 
Take the lead collector metal, and hammer it into a cube. By hammering into a cube, this will eliminate most, if not all of the slag. If there is any visible slag attached to the Lead, it will invariably float to the top of the cupel, disallowing Oxygen to reach the Lead . Even picking off any minicule pieces of slag, will greatly improve the speed of the adsorption Oxygen is necessary to oxidize the Lead, allowing the cupel to adsorb the Lead oxide produced in the reaction of heat and oxygen in the cupellation furnace. The difference in a muffle and cupellation furnace, is the cupellation furnace allows Oxygen in, a muffle furnace is relatively Oxygen free. The old school assay furnaces had a separate chamber for assaying, and another for cupellation. They have several on display throughout Leadville ,Colorado, if you ever get there. It is really neat to see some of these preserved.
 
No idea what I'm doing wrong I smelter it all back into a 130 gram button. I added 20grams of lead in the smelt.

I hammer the button most of it broke off not what lead does.

I picked up 2 3grams bits wrapped in 30 grams lead. Had the cupels in furnace for 15mins at 900
Dropped the samples in. It's been 45min and look to be the same results.
 

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Same results. Any idea's what in doing this was 3gram sample with 30grams lead.
 

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ben2363 said:
No idea what I'm doing wrong I smelter it all back into a 130 gram button. I added 20grams of lead in the smelt.

I hammer the button most of it broke off not what lead does.

I picked up 2 3grams bits wrapped in 30 grams lead. Had the cupels in furnace for 15mins at 900
Dropped the samples in. It's been 45min and look to be the same results.
Click to expand...
If I’m not mistaken the remperature should be higher, try 1050C
Did you buy ir make the coupel dish.
 

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