text: One ancient process for extracting the silver from lead was cupellation.  Lead was melted in a bone ash test or cupel and air blown across the surface.  This oxidised the lead to litharge, and also oxidised other base metals present, the silver (and gold if present) remaining unoxidised.
  In the 18th century, the process was carried on using a kind of reverberatory furnace, but differing from the usual kind in that air was blown over the surface of the molten lead from bellows or (in the 19th century) blowing cylinders.