Silver production. Historical illustration of ancient Japanese workers refining silver from argentiferous (silver containing) lead ore. The furnace consisted of a shallow cavity in a layer of wood ashes. This was enclosed by clay slabs (lower right) forming a small chamber. A charcoal fire was made in this chamber and was used to heat lead ore. When the lead had melted the charcoal was brushed to one side and the molten lead was blasted with air. The resultant oxidized lead was absorbed by the wood ashes leaving a cake of silver (bottom right). This process is known as cupellation. Image from the book Japanese Crafts, Materials and their Applications by B. Hickman.