The term ‘frischen’ as used in the industry refers to a process of reductive smelting. The addition of charcoal reduces metal oxides (litharge) to metals and alloys them together.
The process exploited the greater miscibility of silver in lead than in copper. Coarse copper with silver content was smelted together with lead in a shaft (i.e. vertical) furnace. The tapping gave a mixture of silver-reduced copper and silver-enhanced lead. This mixture flowed into a crucible and solidified into a ‘cake’, which was brought to the liquation hearth after cooling.