When the Romans invaded Britain (now England), they found the Britons making iron in crude furnaces called bloomaries; and not a great deal of improvement, except in size, was made up to Queen Elizabeth’s time, when strict laws had to be enacted to prevent destruction of the forests which were being denuded for production of charcoal, coke, which we know so well, not yet having been produced for fuel.
Milady’s Needle
The Catalan Forge
But the real forerunner of our modern blast furnace was the Catalan forge, developed in and named from Catalonia, north Spain, where it originated. The Catalan, however, and all of such crude early furnaces, including those thus far described, produced a variable kind of what we now know as “wrought iron,” and our modern “cast” iron did not appear until about 1350 when, with larger furnaces, an excess of charcoal, with greater heat and other favorable conditions, the Germans found that the pasty, difficultly melting metal could be made to absorb carbon enough to make it easily fusible. This was the secret.
To state the matter in a simple way, iron ore, which is essentially a natural “iron rust,” is the metal, iron, held in the strong chemical grip of the gas, oxygen, which normally forms one-fifth of the air we breathe. As you note, the combination forms a substance entirely unlike either the iron or the oxygen, but both of these can be regenerated from it (the ore) by chemical methods. Under influence of high heat (this is one of the chemical methods, by the way), this stranglehold can be broken by carbon, of which lampblack, graphite, charcoal, and coke, are our most familiar examples. The result, in the small, crude, and inefficient furnaces of long ago was a disappointingly small ball of crude iron, pasty and scarcely meltable, even at highest heats, but soft and malleable when cold. As mentioned, it was a variety of what is now commonly called “wrought iron.”
A Catalan Forge With Italian Trompe, or Water Blower
The ancients got this far.