My Cupel Split, help Please

[NoIdea]

Hello All – just a quick question on cupellation, if I may please.

During cupellation, my cupel split in two, releasing its contents into the furnace (charcoal fuelled), and settled between the metal wall and air blower pipe, creating the long shaped nugget.



The nugget top of picture was the same material which only partially cupeled before that cupel split also, both occasions were my own stupid impatient self :roll:

The metal that entering the cupel had a noticeable soft lead layer, pictured below, which is now gone.



My question is this: Would the lead have continued cupellation, i.e. did the litharge melt and still remove other oxides and to what possible extent if so?

The nugget is brittle, and snapped into three bits easily.


Thanks

Deano

 

[Westerngs]

The cupel's function is to absorb the lead oxide along with base metal oxides.

When your metal ran out of the cupel, the lead and base metal oxides had nothing to absorb onto, they only thing they could do was evaporate into the atmosphere.

The evaporation rate is very slow, so depending on how long the molten metal was in the furnace, you may or may not have evaporated most of the lead.

It sounds to me like not. Lead in the metal makes it brittle, so your metal still has lead in it. How much, who knows. Your best bet is to re-wrap the metal in lead foil and go through the cupellation process yet again.

Good luck.

 

[NoIdea]

Thanks Westerngs: the reason i asked is that i have read, in more than one place, the term cupellation does not necessarily involve a cupel, the litharge with its collected oxides are allowed to drian off into another vat leaving behind silver and other PM's.

When ever i have melted this material, it would sweat out, at lower temperatures, what appears to be lead, which readily oxidizes to the unmistakable looking/smoking litharge.

Again, Thanks

Deano

 

[Dr. Poe]

You might have left your cupel out in the air where it absorbed moisture. Try storing it in talcum powder.

 

[NoIdea]

Thanks Dr Poe: the breakage occured while moving it in the furnace, i have done this twice now, i think i have learnt my lesson :roll:

Thanks

Deano