3. Reducing ores to a liquid state: smelting

The improvement of primitive furnaces led to the construction of the first "bas-foyers", the most advanced of which are the Catalan bas-foyers. They still operate on the same principle, using iron ore and charcoal, but air is injected into the furnace by means of bellows to activate the combustion of the charcoal and significantly raise the temperature of the charge being processed. Thanks to this rise in temperature, the iron ores are reduced to a liquid state and, for the first time, a new alloy is obtained, which is called cast iron. At first, this carbon-saturated ferrous material turned out to be completely unusable, as it was too hard and brittle, and impossible to shape by forging. A little later, an even more massive injection of air produced an excess of oxygen, which had the effect of eliminating some of the carbon contained in the cast iron, directly in the blast furnace, and...