A finery forge is a specialized hearth used to refine pig iron into more workable iron by removing carbon and impurities. The operation centers on a charcoal- or coal-fired fireplace where molten or pasty iron is exposed to air and heat so that excess carbon burns away. The term often refers not only to the hearth itself but to the small complex of hearth, reheating fire and hammer that together produced bars of wrought iron used in construction, tools and hardware.
How it worked
In a typical finery sequence, molten pig iron was tapped from a blast furnace and placed in the finery hearth. A blast of air encouraged oxidation; operators repeatedly worked a pasty mass by stirring and decanting until the carbon content dropped and a spongy lump of malleable iron remained. That lump was then consolidated by hammering, folding and reheating in a hearth or chafery, producing a denser mass that could be shaped into bloom or bars of wrought iron.
Typical components and steps
- Finery hearth: where decarburization took place
- Chafery: reheating hearth used to bring the iron to hammering temperature
- Hammer or trip hammer: used to consolidate and shape the bloom
- Rolling or smithing: final shaping into bars or finished items
Raw feed was usually pig iron produced in a blast furnace. The finery process removed carbon and some slag, producing wrought iron that was tough and ductile but labor-intensive to make.
History, decline and significance
Variations of finery forges appear in many pre-industrial societies; early forms may date back centuries BCE. From medieval through early modern periods finery forges were widespread in Europe. The method was gradually superseded in the 18th and 19th centuries by puddling and later steelmaking processes that were faster and better suited to coal and coke, leading to the decline of charcoal-dependent fineries. Nevertheless, finery forges played a central role in the development of ironworking technology and the growth of pre-industrial economies.