The Development and Dissemination of the Walloon Method of Ironworking

The Development and Dissemination of the Walloon Method of Ironworking

The use of iron cannon and cast-iron shot developed significantly during the protracted conflict between France and England known as the Hundred Years' War. Within the context of the demand for iron for artillery, important technological developments in ironworking occurred in Wallonia, the French-speaking part of the southern Low Countries (present-day Belgium). These were of particular importance in the county of Namur (annexed to Burgundy in 1429) and made that county, together with Hainaut (annexed to Burgundy in 1433) and the principality of Liège, important suppliers of munitions to combatants in the war.

Through his marriage to Margaret de Male, Duke Philip the Bold of Burgundy became the son-in-law of Count Louis of Flanders, brother-in-law of Count Willem I of Namur, and uncle to the count's son Willem II who served Philip in military capacities in the Low Countries.¹ On the death of Count Louis in 1384 Philip inherited Flanders and other lands in the north, as well as the counties of Nevers and Burgundy that flanked his own duchy of Burgundy in the south.

In 1388, the town walls of Namur had been remodeled to deploy cannon, probably the earliest in Europe to be reconfigured in that way. The first known manufacture of cast-iron shot in Europe came in the county of Namur in 1414, when Danekin Le Feron cast sixty-eight cannon balls at Jausse-les-Ferons for use in the bronze bombards of Master Colart.² Between 1345 and 1445, important developments in the technology of iron occurred in the county and in nearby parts of Wallonia.

Metal produced in a tall furnace was contaminated by carbon from the fuel, thus yielding cast iron that was brittle when cool and therefore useless to a smith. This carbon was removed by oxidation—fined—in the forge, complete oxidation yielding wrought iron, and partial oxidation yielding steel. Since fining did not eliminate all impurities, particularly those arising from the phosphoric or sulfurous ores common in Wallonia, Walloon iron was not suited to every purpose. It did have one distinct advantage, however: it could be produced rapidly and in great quantity, thanks to a forehearth added to the tall furnace that could double the amount of metal produced. The metal itself could be run off from the forehearth as a long sow for conversion into wrought iron at the forge. It could also be ladled out for casting as gunshot or other light castings once the slag that floated on its surface had been broken.

At the forge, the metal was first fined and its cinders extruded before it was drawn out into bars for marketing (a hammer being used in each of the three operations). In Wallonia, manual fining was replaced at the forge by waterpowered bellows, and a large waterpowered great hammer replaced the swifter tail-helve that was used in most other areas. Around 1400, this process spread eastward into metropolitan Liège, into much of Germany, and, around 1540, from Germany into Sweden (where it came to be regarded as a specifically German hearth—a tyskhärd).

Because fining was a more protracted and more sophisticated process than extruding cinders and drawing out, a separate hearth—the finery—was introduced to speed things up. It was soon apparent that by using two fineries a constant flow of fined iron could be produced for the other hearth that became known as the "chafery" (from the French verb chauffer, meaning to heat), and that if all three worked constantly, the entire output of a single furnace could be processed.

Paradoxically, the separate finery that distinguished the Walloon method from the furnace and forge (fourneau et marteau, or Hütte und Hammer) of other types of ironworking seems to have evolved not in Wallonia itself but near its southern border. It then spread rapidly into Namur...