In 1766, Dr Richard Watson described William Champion's zinc-smelting process:

'In a circular kind of oven, like a glass-house furnace, there were placed six pots about four feet each in height... into the bottom of each pot was inserted an iron tube, which passed through the floor of the furnace into a vessel of water. The pots were filled with a mixture of calamine and charcoal, and the mouth of each was then close stopped with clay. The fire being properly applied, the metallic vapour of the calamine issued through an iron tube, there being no other place through which it could escape, and the air being excluded, it did not take fire, but was condensed in small particles in water...'