Oh! the iron!

Then came in sight that man of iron, Charlemagne, topped with his iron helm, his fists in iron gloves, his iron chest and his Platonic shoulders clad in an iron cuirass… All those who rode before him, those who kept him company on either flank, those who followed after, wore the same armour, and their gear was as close a copy of his own as it is possible to imagine. Iron filled the fields and all the open spaces. … This race of men harder than iron did homage to the very hardness of iron. … ‘Oh! the iron! alas for the iron!’

Thus did the late ninth century monk Notker the Stammerer relate the reaction of the Lombard king Desiderius as Charles and his army came into view, waiting in a tower in Pavia for the storm to break. Soon after, according to Notker, one witness literally fainted at the sight of the mighty horde.1.Notker the Stammerer, Two Lives of Charlemagne, bk.II, s.17, pp.163-164.

Where did all this iron come from? Of the many miracles related in dozens of saint’s lives from this period, none mention swords falling from the sky. All of the weapons, armor, and, for that matter tools, farm implements, and horseshoes had to be crafted by hand, using iron ore taken from the earth, and then smelted in villages, manors, and abbeys all through the realm. Let’s take a look at this industry, “of the utmost importance in the Carolingian Empire”.2.Butt, Daily Life in the Age of Charlemagne, p.89.

To us 21st century sophisticates, the extraction of iron ore probably brings to mind images of vast pits visible from space and entire mountains leveled for the ferric (from the Latin ferrum, iron) treasure thereunder. But eighth century mining methods had declined from even the relatively crude and shallow shafts of the Romans. Thus there are few early medieval mines to explore. The Capitulary de Villis confirms this finding, when it references “fossa ferraricia sive plumbaricia.” Loyn translates this as “iron- or lead-workings,” but Verhulst’s “shallow shafts of iron ore and lead” is more accurate.3.Loyn, Reign of Charlemagne, Capitulary de Villis, ch.42, p.70, and Verhulst, The Carolingian Economy, p.76. Many thanks to Dr. Scott Bruce for clearing up this question for me.

Through an odd chemical and biological process, these early metal-workers were probably pulling a fair amount of raw material from swamps.4.“Streams carry dissolved iron from nearby mountains. In the bog, the iron is concentrated by two processes. The bog environment is acidic, with a low concentration of dissolved oxygen. In the acidic environment of the bog, a chemical reaction forms insoluble iron compounds which precipitate out. But more importantly, anaerobic bacteria (Gallionellaand Leptothrix) growing under the surface of the bog concentrate the iron as part of their life processes. Their presence can be detected on the surface by the iridescent oily film they leave on the water, another sure sign of bog iron.” http://www.hurstwic.org/history/articles/manufacturing/text/bog_iron.htm ‘Bog iron’ occurs widely, and can be harvested with simple tools and a lot of work. How much iron was harvested and extracted is a pretty open question, as the entire industry was, like everything else in this era, artisanal. Some records were kept, however, as in the weight of iron ingots that might be due as rent.

The conversion of bog iron into workable iron, known as smelting, was local and small scale. “It is likely that the rather small and strongly decentralised production of iron was processed locally by smiths.”5.Verhulst, The Carolingian Economy, p.77. A study of early medieval Swiss metallurgy found that

From the 6th century onwards, the archaeological evidences indicate the spread of the iron production all over Switzerland. … During the early Middle Ages, the production and working of iron was important in Switzerland. The many tons of reduction slags dated to this period seem to testify to a production sufficient for the needs of the local market. It may even be possible that the country started to export iron to other areas.6.http://www.unifr.ch/geoscience/mineralogie/archmet/index.php?page=775

The goal of smelting is to separate the pure iron, which can be heated and forged into various useful things, from the sand, oxygen, and all the other impurities with which the iron is bound to in the form of ore. To do so a furnace called a bloomery was used, which was essentially an enclosed, upright oven, into which was fed charcoal and the iron ore. A bellows pumped in air to raise the temperature. Inside the bloomery, the hours of high heat debonded the impurities from the iron,

A schematic, not a working diagram

which then sank to the bottom of the furnace. The key was to let the reactions proceed long enough to drive out the bound oxygen from the iron, but not so long that the iron started to bind with the carbon from the charcoal.

Carbon bound with iron is steel, which these days we obviously like a lot, but only because we have blast furnaces. Steel is much harder than iron, and could not be worked with the methods and tools available to the early medieval smith. The only exception was the creation of steel-surfaced swords, which was a special skill, and rendered a weapon worth its weight in gold.

The end result of the smelting process was called a bloom, a mass of red-hot (but not liquid) iron and a bunch of sand and clay, called slag, which the smith would literally pound off of the iron with a hammer. Mounds of worthless slag are one of the archaeological hallmarks of iron production. Anyone interested in a little experimental archaeology can build a backyard bloomery, like these ever-charming English adventurers.

It is no slur to note that modern chemistry was unknown to the medieval smith, who “only knew how, they did not know why, the did certain things.”7.W. K. V. Gale, as noted in Gies, Cathedral, Forge, and Waterwheel, p.63. Crafts were passed from generation to generation, and there was not enough surplus production to allow for a lot of experimentation and improvements.

Obviously smelting was long, hot, fiery work, as was the labor of the blacksmith who would then produce something with the iron. It is no surprise that iron-working was relegated, along with other dangerous or smelly crafts, to the edge of settlements. “Zones for craft activities, particularly metalworking, often appear to have been situated outside the farmyard… The distancing of certain industrial activities involving fire or foul smells (iron-smelting, tanning, and flax retting) from the habitation area must have been for largely practical reasons.”8.Hamerow, Early Medieval Settlements, p.85. In other words, keep that stuff downwind and downstream.

The smith, with his reasonably pure iron and his workshop outside the settlement, was now ready to get to work. And work he did. While “Carolingian civilization was based on wood,”9.Riche, Daily Life, p.147. the smith turned out a steady supply of  “axes, adzes, daggers, and knives. … Horseshoes were made of iron, as were plow points, scythes, sickles, bill hooks, and knives for agricultural work. … Among artisans, smithing hammers, knives, chisels adzes, saws, scissors, and other specialized tools and implements were made of iron. … so were nails, as well as iron bands, clamps, and hinges. Church bells were also made of hammered iron rather than bronze or brass.”10.Butt, Daily Life in the Age of Charlemagne, p.90. The Capitulary de Villis demands “good barrels bound with iron.”11.Loyn, Reign of Charlemagne, Capitulary de Villis, ch.68, p.73.

The Pippinid war machine required weapons and armor in large quantities, and these were produced in surprising places. While blacksmiths were essential and widespread, sword and shield makers are also recorded at the abbeys of Lorsch and Fulda.12.Verhulst, p.79. The plan of St Gall puts the blacksmiths, fullers, and goldsmiths at the edge of the abbey, in a “great collective workshop,” also occupied by the shield makers and sword grinders.13.Price, Plan of St Gall, p.53. Today that would make for eye-opening sight, a munitions factory on the local church grounds.

Blacksmiths were clearly a vital part of the workings of the early medieval era, and even the law reflected that reality. The Laws of the Alamans include a chapter specifically concerned with the killing of a blacksmith or silversmith,14.Rivers, Laws of the Alamans and Bavarians, p.94. although, we should note, the Lombard, Salic, and Burgundian laws do not.

It is probably true, though not explicitly mentioned in the sources, that in those areas with raw material available the smith controlled the production of iron from the bog to the customer. What we would call a vertically integrated enterprise. But there must also have been a good trade in iron ore and raw iron, for there were blacksmiths everywhere, but only randomly placed sources of iron ore.

While the early medieval era was not the iron age, iron was a part of everyday life for virtually everyone. Medieval life would not have been possible without it.

Footnotes   [ + ]

1. Notker the Stammerer, Two Lives of Charlemagne, bk.II, s.17, pp.163-164.
2. Butt, Daily Life in the Age of Charlemagne, p.89.
3. Loyn, Reign of Charlemagne, Capitulary de Villis, ch.42, p.70, and Verhulst, The Carolingian Economy, p.76. Many thanks to Dr. Scott Bruce for clearing up this question for me.
4. “Streams carry dissolved iron from nearby mountains. In the bog, the iron is concentrated by two processes. The bog environment is acidic, with a low concentration of dissolved oxygen. In the acidic environment of the bog, a chemical reaction forms insoluble iron compounds which precipitate out. But more importantly, anaerobic bacteria (Gallionellaand Leptothrix) growing under the surface of the bog concentrate the iron as part of their life processes. Their presence can be detected on the surface by the iridescent oily film they leave on the water, another sure sign of bog iron.” http://www.hurstwic.org/history/articles/manufacturing/text/bog_iron.htm
5. Verhulst, The Carolingian Economy, p.77.
6. http://www.unifr.ch/geoscience/mineralogie/archmet/index.php?page=775
7. W. K. V. Gale, as noted in Gies, Cathedral, Forge, and Waterwheel, p.63.
8. Hamerow, Early Medieval Settlements, p.85.
9. Riche, Daily Life, p.147.
10. Butt, Daily Life in the Age of Charlemagne, p.90.
11. Loyn, Reign of Charlemagne, Capitulary de Villis, ch.68, p.73.
12. Verhulst, p.79.
13. Price, Plan of St Gall, p.53.
14. Rivers, Laws of the Alamans and Bavarians, p.94.

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