Henry Bessemer converter development (1856)

Bessemer figures out how to make tons of steel rather than hundreds of pounds; ~10 years of process perfection; the inflection point Tom uses to mark "the Iron Age." Note: a related but distinct entry exists in the canon ("Basic oxygen furnace introduction in Austria"); Bessemer's converter is the prior generation.

The history of steelmaking is that, because we couldn't melt it until Henry Bessemer came along and taught us how to melt steel at 1500 degrees centigrade, we actually made two types of steel, called wrought iron and cast iron. If you heated the iron ore up to below 700 degrees centigrade with charcoal, the charcoal would form carbon monoxide, and the carbon monoxide would react with the iron oxide — or the carbon would react to form carbon monoxide and iron — and you would end up with this solid sponge. It was just like a steel sponge: it had bits of charcoal, bits of limestone, and a blacksmith would take that chunk and forge it. He'd put it in the heat, heat it up to a red heat, and he'd hammer it and weld that sponge together. As he did, the charcoal would burn or oxidize away, or flake off if it was a big chunk, and the limestone would come out. You'd end up with something that had quite a few limestone inclusions, but you'd end up with a wrought iron that was bendable, that was ductile — the same type of wrought iron we know today.