The Medieval Roots of Colonial Iron Manufacture Technology

Iron Manufacture in Medieval Europe

Iron manufacture in the Middle Ages was comprised of essentially three practices: mining, smelting and smithing. As will be argued in more detail below, these practices were basically identical to those used in colonial America. In effect, mining is the extraction of an ore or minerals, for example iron ore, from the earth, generally by means of tunneling or excavation. Although much of the earliest iron ore used in Europe was found in exposed areas of earth that did not require much digging, these surface deposits were exhausted by the twelfth century and means of acquiring the increasingly popular and deeper buried iron ore needed to be devised. Much of what we know today about medieval mining methods comes from the great textbook on mining, De re metallica ( On metallic matters ), written in 1556 by Georgius Agricola, otherwise known as Georg Bauer. From this text, we know that the technology developed for mining in the Middle Ages included tools for digging and splitting rock, hauling implements, drainage pumps and ventilating machines. Necessary for the initial stages of the mining process, a miner's tools were generally constructed of iron with wooden handles and included a shovel, pike, hoe, pick, hammer and wedge. The ore reaped by these tools then needed to be hauled to the surface through a variety of means. Buckets, wooden and ox-hide bound by iron, were the basic ore-moving device. Other hauling implements, such as windlasses, employed cranks powered both by man and by animals. A labor-saving innovation particular to the Middle Ages was the wheelbarrow, allotting one man the transporting power of two. This search for labor-saving devices was characteristic of medieval man, as well as the American colonist, and will be addressed in further depth below. Another example of this style of thinking was the invention of the wagon mounted on wooden rails and drawn by animal power, an early forerunner of the locomotive.

Complications in the mines, such as flooding and ventilation difficulties, inspired medieval miners to create often inventive means of overcoming them. Agricola wrote that mines were most often not abandoned because they were barren of ore, but because they were flooded. [1] In response to flooding, drainage pumps were devised for the removal of water from the mine. The simplest type of pump was a series of dippers attached to a chain. These were powered by animals on treadmill, hand and even by waterwheel. Waterwheels also powered the more sophisticated suction-pumps, which drew by means of pistons. A third type, rag-and-chain pumps, were powered manually and used balls stuffed with horsehair, spaced along the chain, that acted as one-way pistons. Delving deeper beneath the surface of the earth led to a second complication for the miners: less oxygen for those working in the elongated tunnels. Rather than limit the depth that the mines could extend, ventilating machines were developed as a solution. The simplest form of ventilation, sufficing only for the shallower mines, was merely the flapping of cloths to circulate air. Later, revolving fans and single- or double-acting bellows maintained air flow, while allowing miners to dig to new depths.

Workers in the mines also followed a particularly medieval form of labor organization. The first "customs of miners" was recorded in Trento in 1185, closely resembling the medieval manorial pattern of agriculture. A seam of ore was allotted to each family of miners, who followed the guidance of their lord, the landowner. The lord decided the working methods, hours and profit distribution. [2] This organizational scheme is strikingly similar to that of the better-known medieval agricultural manor.

Smelting was the second of the three basic steps of iron manufacture. Basically, smelting is the process of melting down ore in order to separate its metallic components from impurities. Charcoal, technically charred wood, was the predominant heating source of the Middle Ages, the abundance of wooded acreage across Europe making it the easiest and most transportable, if not most efficient, resource for smelting and blacksmithing. Lime flux, usually either limestone or oyster shells, was often added in order that it would combine with impurities to create a brittle slag, the residue formed through the oxidation of the iron due to smelting. [3] Smelting took place in the furnace, a number of varieties appearing during the Middle Ages. The most primitive of these was the bloomery hearth. Here the ore was covered with charcoal and held together by a circle of stones. A bellows, invented in the early Middle Ages, supplied a draft of air towards the middle of the hearth. The Corsican and Catalan forges improved upon the bloomery hearth's design by utilizing more permanent masonry walls on two or more sides. The subsequent Stückoven, however, remained the most advanced furnace until the fourteenth century, and in many areas, the sixteenth, increasing output to as much as three times the earlier furnaces. Its masonry construction reached heights of ten to fourteen feet and often employed a water-driven bellows. The use of waterpower, though, reached its pinnacle in the blast furnace, referred to by some as the "greatest technical achievement of the period." [4] Although the Chinese developed a waterpowered blast furnace whose technology spread as far west as Persia, it is believed that the technology was probably developed independently in Europe, the earliest known example being at Lapphytten, Sweden in 1350. [5] The blast furnace's waterpowered technology increased combustion and allowed the iron to be held in contact with the charcoal, producing a higher carbon content with a low melting point. The effect of this magnified dependence on waterpower, particularly in iron manufacture, can be seen in the great increase of laws and lawsuits after 1300 in regard to navigation rights versus power rights. [6] Dams and millraces were constructed on ever larger rivers, rather than limit their power consumption to only tributaries and small rivers.

The greatest benefit permitted by the blast furnace was that the iron could be handled to easily produce pig iron or wrought iron at will. The term "pig iron" comes from the image of the molten iron that separated from the slag, ran into a canal of sand, called a "runner," and on into shallow, radiating depressions. The depressions reminded medieval iron workers of a sow with suckling pigs. Although this choice between pig and wrought iron was possible in some previous furnaces, the quality of the blast furnace's iron greatly exceeded anything seen before, with a much greater efficiency and higher percentage of iron from the ore. The waterwheel powered enormous pairs of bellows that alternatingly blew through an opening in the furnace called a "tuyere." This greatly increased the draft into the furnace and thereby the temperature; higher temperatures meant that the ore was heated to a point where the carbon uptake was intensified, turning out an alloy of about 4% carbon and 96% iron. Not only the greater efficiency of the blast furnace, but also its ability to run continuously, allowed for a marked increase in output; the waterpowered blast furnace could run for weeks or even months at a time.

Blacksmithing during the Middle Ages experienced not only an increase in demand, but also an increase in technological innovation. By the sixteenth century, blacksmiths worked not only in the castle's armory, but had also moved into towns and villages, supplying the increasingly popular iron housewares and farming implements. One result of this was that a peasant in the later Middle Ages was now much more likely to have a full set of farming tools than his ancestors a century or two before. [7] Some of the most common iron pieces commissioned of a blacksmith included cooking utensils, carpenter's nails, spurs, fire tongs, hinges, tips for spades, parts for axles, the multifunctional cauldron, as well as blades for sickles, scythes, axes, adzes and mattocks. Repairs of every nature and sharpening of tools also made up a huge portion of the blacksmith's business.

Our knowledge of medieval blacksmithing techniques is largely derived from the work of Benedictine monk, Theophilus Presbyter, believed to be Roger of Helmarshausen. His three-part text, De diversis artibus ( On diverse arts ), written around 1122, gives a detailed description of "The Art of the Painter," "The Art of the Worker in Glass," and, obviously his personal favorite, claiming two-thirds of the entire book, "The Art of the Metalworker." He describes the appearance of the workshop, how to work at the forge, and how to make an array of metalworking tools, including bellows, anvil, hammer, tongs, wire drawplate, punch, chisel and pliers. An excerpt from his text describes the use of iron:

The smithing process generally followed the same pattern as laid out by Presbyter, with a few variations, depending on the desired product. The piece was first heated in the charcoal-fueled forge, made hotter by the draft from a bellows, then hammered out on an iron anvil usually mounted on a short tree stump. An assistant, often an apprentice, regularly helped with the first stages of hammering by wielding the sledgehammer while the smith positioned the hot iron piece. Later, it was refined with smaller hammers, punch, lathe, grindstone, files and chisels. Chisels varied, depending on whether they would be used on hot or cold metal; the "cold" chisels needed to have a much harder edge. Fabricating tools that would later be used to cut hard materials, like stone or metal, also required tempering, a process of repeated heating and quenching, to provide hardness and ductility. Because of its time-consumption, tempering was reserved for only the tools that absolutely required it, like those mentioned or for weaponry. In addition to the work done on cast iron, the pig iron supplied by the new blast furnaces could also be converted into wrought iron through the practice of reheating and hammering at the forge. This practice gained popularity throughout the fifteenth and sixteenth centuries.

The most significant technological innovations in blacksmithing during the Middle Ages, however, came from the application of natural forces to metalworking machines. The waterwheel supplied the power for numerous new devices, including the tilt- or trip-hammer, which hammered an iron head attached to a wooden shaft onto a sprung beam, whose recoil added to the power of the stroke. Water also supplied a solution to the increasing demand for nails: the slitting mill. An ancestor of the rolling mill, its two rotary disks cut iron into slender rods that could quickly be transformed into nails by the smith. Wire-drawing also became significantly easier with a series of inventions surrounding the drawplate and culminating in the addition of waterpower. In the early Middle Ages, wire for chain mail and other applications had been painstakingly hammered out by hand. Beginning in the tenth century, smiths began using a drawplate, through which a series of gradated conical holes were cut, allowing the wire to be easily pulled into shape. The addition of waterpower in the fourteenth century brought about the full realization and efficiency of this technology.