When we studied world history in high school, we learned that the evolution of civilization had a major setback in the fifth century AD when the Barbarians overthrew the Roman Empire and Europe entered the Dark Ages. All attempts at learning and science were suspended and massive amounts of knowledge were lost forever. It took a millennium and the arrival of the Renaissance for it to get back on track. Recently I have learned that this perception may have been grossly exaggerated.
This realization began with watching “The Dig”, an excellent recent British movie. It documents an important archaeological excavation in the late 1930s on the east coast of England. A wealthy English lady named Edith Pretty was convinced that a series of small hillocks on her estate (Suffolk Hoo) were burial mounds. This was confirmed when one of them yielded remnants of a longship and a chamber containing metal artifacts including a bejeweled sword. When contemporary experts examined the findings, they concluded that this was the tomb of an Anglo-Saxon king from the seventh century. Based on the technology exemplified by the artifacts a representative of the British Museum concluded that the Dark Ages weren’t that dark after all.
The sword was a prime example of this technology. It had all the characteristics of the Damascus sword, a fearful weapon that Crusaders encountered centuries later. This led me into a fascinating rabbit hole, the investigation of ancient swordsmithing and steelmaking. When I taught “Materials of Construction” to Civil Engineering students at Pitt, I always dedicated a lecture to the evolution of steelmaking. I discussed “bloomeries”, “wootz steel”, and “crucible steel” without having any real knowledge of what the terms meant.
By definition, steel is an alloy of iron and a small amount of carbon, with traces of other metallic elements. Pure iron is very soft and virtually useless. The addition of carbon facilitates the production of many different grades of steel with a variety of desirable characteristics, up to a point. When too much carbon (more than two percent) is added, the net result is a very brittle material we call cast iron. Today we produce iron in great quantities in blast furnaces where iron ore (iron oxide) is melted in conjunction with coke (carbon) and limestone. The resulting “pig iron” is then refined in an electric arc furnace or basic oxygen vessel where the excess carbon is removed, resulting in the desired steel composition.
Prior to the seventeenth century iron was produced in bloomeries, small masonry furnaces where iron ore and charcoal (carbon) were heated together to a temperature (below the melting point of iron) at which the oxide was reduced (the oxygen combining with carbon to form carbon monoxide). After several days the furnace was allowed to cool down and lumps (blooms) of “sponge iron” were scraped out of the ashes. The blooms were porous agglomerates of iron, carbon, and slag (other elements in the ore, primarily silicates). Blacksmiths then would reheat the bloom till it was “cherry red” and hammer it vigorously to drive off the excess carbon and slag. This was repeated many times, frequently folding thin bars into thicker workpieces, until the desired composition was achieved. Forging the piece into the desired shape (sword, plow blade, etc.) required many additional reheating cycles. The result was a respectable steel tool.
Around 500 BC an alternative technology, crucible steelmaking, was developed in India. There the blooms were broken up into acorn sized pieces and intermixed with charcoal and improbable ingredients specified by alchemists (nuts, pomegranate leaves, salt, orange peel, egg whites, etc.!) and placed in a small (six-inch diameter by six inches long) clay crucible with a sealed lid. The crucible was then placed in a furnace with a temperature above the melting point of iron and roasted for several hours. The resulting ingot was shaped into a bar and marketed throughout the Levant and Europe as “wootz steel”. By the time of the Crusades skillful swordsmiths in Damascus had perfected the technology to produce “Damascus steel” swords with the sharpest edges ever achieved, perfect for beheading infidels. In addition, when finely polished, these blades also possessed an attractive, unique surface pattern. A few years later this technology was lost, and Damascus swords became historical artifacts.
Metallurgists have attempted to replicate the manufacture of Damascus swords unsuccessfully for centuries; the secret appears to have died with the demise of alchemy. The most interesting recent attempt is by an unlikely trio – academic metallurgist Dr. John Verhoeven, prominent bladesmith Al Pendray, and retired Nucor executive William E. Dauksch. They have theorized that the original ore used in India to produce wootz steel included a tiny amount of vanadium, the precise amount required to promote the growth of carbides and that these carbides precipitated in a phase, pearlite, that provided the finished product with remarkable hardness and ductility. The alternating layers of ferritic iron and pearlite also produced the attractive dark and light surface bands for which Damascus steel is famous. Iron carbide (aka cementite) possesses the ideal properties required for a sharp blade. At a one and a half percent carbon content these properties are maximized. Based on this knowledge the trio has successfully produced blades very similar to the very best Damascus steel swords. They suspect that, once this specific ore was mined out, the production of wootz steel ended, and so did Damascus steel.
As for our original subject, the Dark Ages, it is difficult to believe that civilization had suffered a setback when realizes that during that era Saxon artisans were still able to acquire wootz steel from faraway India and forge a blade like the one that the archaeologists found in Suffolk Hoo. Our perception of that time period is based upon a perspective that Rome was civilized, and the rest of the world was backward; it is time for us to rethink that philosophy.