Cupels burnt during cupelation

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ogclabsup

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Apr 23, 2017
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Does anyone know what would cause the cupels to look like this after cupeling?

The ones that look burnt are Flash Con, Rougher Con and CIL 1 Feed.
 

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The blackish stuff is likely from impurities of in the metallic button. (i.e. impurities other then lead or precious metals)
 
I assume these were ore samples? If there was a high level of base metal the fusion may not have oxidized enough of it leaving the lead for cupellation loaded with base metals which causes that black crust.
Have you tried scorification of the lead cone from the fusion before cupellation?
 
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