Damascus Steel
by Friar Thomas Bacon (David Moreno)
Orignally published in the May 2002, A.S. XXXVII issue of the Dragonflyre, a publication of the Barony of Vatavia.
During the Middle Ages the sword was the weapon par excellence. It defined who was or was not a warrior. In many legends of the period, the hero is signified by as much by the exceptional sword he carried as any other characteristic. Thus any sword of unusual characteristics was held in some awe. Such was the case of swords made from Damascus steel. Such swords were unequaled in durability and sharpness. The fact that the manner of their manufacture was a tightly held secret only added to their mystic. So tightly held that it has become lost. Modern metallurgical analysis has shed some light on this mystery, the results of which I will summarize below.
The name Damascus is a bit of a misnomer. While such blades were made in Damascus, most were made in Persia. The name results from Europeans not encountering this material till the Crusades with the mistaken belief that all such blades came from Damascus. The earliest mention of these blades is from around 540 AD though they could be seven centuries older. The manufacturing of the blades ended around 1800. While blades are the best known things made out of Damascus steel; shields, armour, axes and spearheads were also constructed.
Damascus steel is classified as a high carbon steel, containing two to three times more carbon then ordinary steel. Such steels are normally brittle. That Damascus steel is not is what makes it so intriguing. What is most immediately obvious about Damascus steel is the light and dark banding, called damask, on their surface. The dark bands are a form of steel known as martensite while the white bands are formed from iron carbide also known as cementite. It this intermingling of these two forms which create the exceptional qualities of Damascus steel. They constitute a form of metal composite that combines the flexibility of martensite with the hardness of cementite without the associated brittleness.
The mystery behind Damascus steel is how to work this material. The raw material originally came from Indian foundries and called wootz. They came in the form of hockey pucks about four inches in diameter and two inches thick. But when European smiths attempted to forge items out of this, or repair Damascus blades, the result was always the destruction of the material.
The trick is the temperature at which the material is forged. Standard low carbon steels are usually worked at between 1200C to 900C (white to orange heat). But at these temperatures, cementite dissolves into partially molten austenite, thus allowing the item to loss structural integrity. Thus it falls about while being hammered. To prevent this it is necessary to heat it to only 850C to 650C (cherry to blood red heat).
There is one other distinction to be made. There is a second method, which produces surface markings similar to that of Damascus steel. Called either pattern welding or forge welding, it involves placing together alternating sheets or rods of low and high carbon steel, which is then twisted and hammered together. This produced what is sometimes called ‘false damascene’. The properties of this material are similar to Damascus steel but have a very different microstructure.
The microstructure of Damascus steel is characterized by alternating layers of cementite. This banding is the result of repeated cycles of heating and forging needed to form a blade from an ingot of wootz. The precise mechanism of how this occurs is under dispute. One source has this as the result of the mechanical breakup and compression of the cementite network into spheroidal particles. Another source attributes this to the cementite precipitating out around minor impurities in the steel. Not all impurities have this effect. So one suggestion why the production Damascus steel items stopped is the that the imported wootz quit having these critical impurities. The characteristic banding stopped appearing so the craftsman stopped using the related techniques.
There are two final steps in the making of a Damascus blade. The first is heat treatment. During the course of forging, most of the low carbon steel is in the form of rather weak ferrite. The process of heating then quickly cooling converts this ferrite into the harder martensite. Medieval smiths had a number of curious recipes for the proper quenching methods, the most notorious being plunging the heated blade into the body of a slave. Whether this was actually done remains unrecorded.
The second step is etching the blade with acid. For it is only then that the damask pattern emerges. Two special patterns can be found on blades. The more common has the damask form a series of parallel lines known as Mohammed’s ladder. The older pattern has the damask in a circular swirl called a rose. There are several theories how they were done using various forging tricks as the blade took final form.
In an age when the average sword was quickly bent, nicked, and blunted in the course of a single battle, Damascus became legendary for their resilience and ability to keep a fine edge. The legend of such a blade being able to cut a silk handkerchief as it floated in air is an invention of Sir Walter Scott. But it is indicative of the superior quality of the blades. That they are now considered high value art items have made it difficult for scientific inquiry to crack their mystery. That has not stopped people since Michael Faraday to claim to have found the secret. While it is now possible to create items that could pass for Damascus steel items, whether the techniques used truly imitate the originals will never be known.
Bibliography
Nicolle, David. Medieval Warfare Source Book: Warfare in Western Christendom. London: Brockhampton Press, 1995.
Sherby, Oleg, and Jeffrey Wadsworth. "Damascus Steels." Scientific American Vol. 252. February 1985: 112-120.
Underwood, Richard. Anglo-Saxon Weapons and Warfare. Stroud: Tempus Publishing, 1999.
Verhoeven, John. "The Mystery of Damascus Blades." Scientific American Vol. 284. January 2001: 74-79.
Copyright © 1997 - present His Lordship Friar Thomas Bacon (David Moreno). All rights reserved.