|Scraps for melting on the right, consolidated cakes on the left|
The other purpose of hearth-melting is to change the chemical makeup of a batch of steel. There in the furnace at temperatures between welding and melting, where fundamental bonds dissolve and form in a whirlwind dance of elemental cataclysm, iron, carbon, oxygen and other ingredients strap together and tear apart. The product of this storm is determined by overall mixture of fuel and air, temperature and time. The fuel is charcoal and the air is forced into the side by bellows or blower, though a slanted pipe called a tuyere.
We built our furnace out of easily-disassembled firebricks under Jack's coal-forge hood. There was a bed of ash inside it and a hole in one of the bricks for the tuyere to poke though. We built a fire with wood and then started piling on the charcoal once it was going. After that, we started adding our scraps piece by piece. Mostly we had broken up old saw blades, pitchfork tines, and other pieces of formerly high-carbon steel. It was sort of an experiment to see how high-carbon our product would be if we used high-carbon source material, but our conclusion was that the environment of the fire mattered more than the material.