Before revision: Pig iron was not produced in Europe before the Middle Ages .
After revision: Small prills of pig iron dispersed in slag are produced in all iron furnaces, but the phase transition of the iron into liquid in the furnace was an avoided phenomenon: these globules are not malleable so can't be hammered in a single piece, and decarburizing the pig iron into steel was an extremely tedious process using medieval technology, so in Europe before the Middle Ages