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the blast furnace developed before 1350 and the trip hammer, both of which will be
discussed later (Gies 1994: 199-201).
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The waterwheel provided power advantage to those with access to moving water.
Not all of Europe had such access. To meet power needs, other devices were created,
still working on the principle of using a moving medium to turn a wheel. The tidal mill,
dating back to at least seventh-century Ireland, utilized the tidal motion of bodies of
current-less water, such as harbors or lagoons. They were limited by the eccentric and
limited hours of operation, six to ten hours a day during times of fast tidal change (Gies
1994: 117). Another and more widely used alternative was wind power. The European
vertical windmill was independently developed in the last part of the twelfth century,
though other cultures had developed windmills previously. It featured a tall vertical
wheel, using a shield to divert wind from one half of the wheel. The wind incident on the
other half caused motion similar to that of the watermill. The wheel had to be able to
turn in order to face into the wind, so it was constructed on a stout pole capable of
rotation by laborers (Gies 1994:117). Both of these devices, though, were intended
primarily for grain milling.
Metallurgy
Iron was used throughout the Middle Ages in tools for many professions. Most
important were its uses in agriculture and arms. The former allowed more efficient
production of staple foods, while the latter provided strengthened military power.
Wrought iron was widely used for creation of these tools, along with arms and
armor (Gogan 1999: 28). It was malleable, ductile, and relatively resistant to atmospheric
corrosion. When iron was mined, it consisted of impure iron oxide in an ore. A long
process of purification commenced, first by breaking the ore and physically selecting the
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reddish-brown iron oxide, then by roasting to remove sulfur, and finally by smelting.
During the smelting process, pieces of iron oxide, along with heavily carbonous
materials, such as charcoal, and another material known as a flux were placed together in
a bloomery hearth. The hearth was heated, assisted by a bellows. The carbon would
combine with the oxygen in the iron and rise off as carbon monoxide. The flux material
would gather other impurities, and would be poured off as slag. Remaining in the hearth
would be the bloom of iron, and the remains of the charcoal and slag. The iron would be
removed, and somewhat purified by heat and beating, though the final product contained
inclusions and alloys still. Finally, it could also be forged by beating, usually at high
temperatures.
The blast furnace greatly increased the rate of iron production in the Middle Ages.
It was definitely in use by 1350, and may have been in use earlier. Assisted by
waterpowered bellows, the blast furnace also incorporated a greatly improved
architecture, with a vertical chimney that first widened at an angle and then narrowed
more slowly. The intense heat of the blast furnace allowed carbon to combine rapidly
with the iron, forming an alloy of carbon and iron with a much reduced melting point
(Gies 1994: 201). This pig iron, or cast iron, could be cast into a mold for relatively
quick production of metal products, though this metal was brittle, and therefore not
suitable for arms production.
The pig iron could also be remelted in order to more efficiently produce wrought
iron of a higher purity than bloomery iron. The pig iron would be placed in a similar
furnace, a finery, with two bellows. One would supply oxygen for heating, the other
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would supply oxygen to combine with the carbon to leave the pure wrought iron. Thus
wrought iron could be produced with less labor and cost (Gies 1994: 202).
Steel was harder than iron, which made it more desirable for production of
weapons. Steel is an alloy of carbon and iron, usually in a ratio of about 1.7% to 98.3%
respectively. The first European steels were merely surface deep, called blister steel or
carburized iron. To produce it, iron was strongly heated in contact with a high carbon
material, such as charcoal, in an atmosphere weak in oxygen. The surface of the iron
would become carburized, and thus would be stronger (Gogan 1999: 33,4). The
temperature required for this process to take place is called the transition temperature for
the steel. Blister steel was often used for cutlery and edged weapons when crucible steel
- more expensive, but higher quality was unavailable or too expensive.
Crucible steel, rare if not non-existent in Medieval Europe, was produced by
taking wrought iron and placing it into a closed container with carbonaceous materials,
such as charcoal. The carbon could diffuse throughout the molten iron, allowing steel to
form uniformly (Gogan 1999:45).
Steel had the advantage that it could be further hardened by repeatedly heating,
beating, and quenching it. It was only the existence of the carbon in the metal that
allowed this, so pure iron could not be so hardened. In fact, the degree to which the
hardening was possible was proportional to the amount of carbon, up to a cutoff of 0.9%.
After this point, increased carbon content would not result in increased capacity for
hardness.
To harden steel, the steel piece was heated above the transition temperature and
allowed to remain for approximately one hour per inch of thickness. This allowed the
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heat to permeate the material. Afterwards, the steel would be quickly quenched in a cool
material, such as room temperature water. The more quickly the metal was cooled, the
harder the steel could be made. The price was brittleness; the harder the steel was made,
the more brittle it would become.
To combat this phenomenon, smiths tempered the steel. It was again heated, but
at a temperature below the transition temperature. Then the steel was allowed to cool
slowly, for example by sitting in room-temperature air. Through this method, brittleness
was decreased while retaining hardness.
If the smith wished to soften the steel, perhaps to cut it, then a process similar to
hardening called annealing was used. To anneal the steel, it would be heated to a
temperature higher than the transition temperature, again for about one hour per inch of
thickness. Afterwards, the steel would be cooled slowly, perhaps in room temperature
air. When cooled, the steel would be soft compared to recently forged steel (Gogan
1999: 109, 110).
The quality of the steel produced in some areas was superior to that produced
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