Damascus Steel: Ancient Sword Making Techniques

Damascus steel and Persian watered steel are common names for high-carbon steel swords created by Islamic civilization craftsmen during the middle ages and fruitlessly lusted after by their European counterparts. The blades had a superior toughness and cutting edge, and they are believed to have been named not for the town of Damascus, but from their surfaces, which have a characteristic watered-silk or damask-like swirled pattern.

It's hard for us to imagine the combined fear and admiration engendered by these weapons today: Fortunately, we can rely on literature. The British writer Walter Scott's 1825 book The Talisman describes a recreated scene of October 1192, when Richard Lionheart of England and Saladin the Saracen met to end the Third Crusade. (There would be five more after Richard retired to England, depending on how you count your crusades). Scott imagined an arms demonstration between the two men, Richard wielding a good English broadsword and Saladin a scimitar of Damascus steel, "a curved and narrow blade, which glittered not like the swords of the Franks, but was, on the contrary, of a dull blue colour, marked with ten millions of meandering lines..." This fearsome weapon, at least in Scott's overblown prose, represented the winner in this medieval arms race, or at least a fair match.

Damascus Steel: Understanding the Alchemy

The legendary sword known as the Damascus steel intimidated the European invaders of the 'Holy Lands' belonging to the Islamic civilization throughout the Crusades (1095–1270 CE). Blacksmiths in Europe attempted to match the steel, using the "pattern welding technique," forged from alternated layers of steel and iron, folding and twisting the metal during the forging process. Pattern welding was a technique used by sword-makers from around the world, including Celts of the 6th century BCE, Vikings of the 11th century CE and the 13th-century Japanese samurai swords. But pattern welding wasn't the secret to Damascus steel.

Read More

Damascus Steel Facts and Naming

By Anne Marie Helmenstine, Ph.D.

Some scholars credit the search for the Damascus steel process as the origins of modern materials science. But the European blacksmiths never duplicated the solid core Damascus steel using the pattern-welding technique. The closest they came to replicating the strength, sharpness and wavy decoration was by deliberately etching the surface of a pattern-welded blade or decorating that surface with silver or copper filigree.

Wootz Steel and Saracen Blades

In middle age metal technology, steel for swords or other objects was typically obtained through the bloomery process, which required heating the raw ore with charcoal to create a solid product, known as a "bloom" of combined iron and slag. In Europe, the iron was separated from the slag by heating the bloom to at least 1200 degrees Celsius, which liquified it and separated out the impurities. But in the Damascus steel process, the bloomery pieces were placed into crucibles with carbon-bearing material and heated for a period of several days, until the steel formed a liquid at 1300–1400 degrees.

But most importantly, the crucible process provided a way to add high carbon content in a controlled manner. High carbon provides the keen edge and durability, but its presence in the mixture is almost impossible to control. Too little carbon and the resulting stuff is wrought iron, too soft for these purposes; too much and you get cast iron, too brittle. If the process doesn't go right, the steel forms plates of cementite, a phase of iron which is hopelessly fragile. Islamic metallurgists were able to control for the inherent fragility and forge the raw material into fighting weapons. Damascus steel's patterned surface appears only after an extremely slow cooling process: these technological improvements were not known to the European blacksmiths.

Damascus steel was made from a raw material called wootz steel. Wootz was an exceptional grade of iron ore steel first made in southern and south-central India and Sri Lanka perhaps as early as 300 BCE. Wootz was extracted from raw iron ore and formed using the crucible method to melt, burn away impurities and add important ingredients, including a carbon content between 1.3–1.8 percent by weight—wrought iron typically has carbon content of around 0.1 percent.

Modern Alchemy

Although European blacksmiths and metallurgists who attempted to make their own blades did eventually overcome the problems inherent in a high-carbon content, they could not explain how ancient Syrian blacksmiths achieved the filigreed surface and quality of the finished product. Scanning electron microscopy has identified a series of known purposeful additions to Wootz steel, such as the bark of Cassia auriculata (also used in tanning animal hides) and the leaves of Calotropis gigantea (a milkweed). Spectroscopy of wootz has also identified tiny amounts of vanadium, chromium, manganese, cobalt, and nickel, and some rare elements such as phosphorus, sulfur, and silicon, traces of which presumably came from the mines in India.

Successful reproduction of damascene blades which match the chemical composition and possess the watered-silk decoration and the internal microstructure was reported in 1998 (Verhoeven, Pendray, and Dautsch), and blacksmiths have been able to use those methods to reproduce the examples illustrated here. Refinements to the earlier study continue to provide information about complex metallurgical processes (Strobl and colleagues). A lively debate concerning the possible existence of a "nanotube" microstructure of Damascus steel developed between researchers Peter Paufler and Madeleine Durand-Charre, but nanotubes have been largely discredited.

Recent research (Mortazavi and Agha-Aligol) into Safavid (16th–17th century) openwork steel plaques with flowing calligraphy were also made of wootz steel using the damascene process. A study (Grazzi and colleagues) of four Indian swords (tulwars) from the 17th through 19th-centuries using neutron transmission measurements and metallographic analysis was able to identify wootz steel based on its components.

Sources

• Durand-Charre, M. Les Aciers Damassés: Du Fer Primitif Aux Aciers Modernes. Paris: Presses des Mines, 2007. Print.
• Embury, David, and Olivier Bouaziz. "Steel-Based Composites: Driving Forces and Classifications." Annual Review of Materials Research 40.1 (2010): 213-41. Print.
• Kochmann, Werner, et al. "Nanowires in Ancient Damascus Steel." Journal of Alloys and Compounds 372.1–2 (2004): L15-L19. Print.
• Reibold, Marianne, et al. "Discovery of Nanotubes in Ancient Damascus Steel. "Physics and Engineering of New Materials. Eds. Cat, DoTran, Annemarie Pucci and Klaus Wandelt. Vol. 127. Springer Proceedings in Physics: Springer Berlin Heidelberg, 2009. 305-10. Print.
• Mortazavi, Mohammad, and Davoud Agha-Aligol. "Analytical and Microstructural Approach to the Study of Historical Ultra-High Carbon (Uhc) Steel Plaques Belong to the Malek National Library and Museum Institution, Iran." Materials Characterization 118 (2016): 159-66. Print.
• Strobl, Susanne, Roland Haubner, and Wolfgang Scheiblechner. "New Steel Combinations Produced by the Damascus Technique." Advanced Engineering Forum 27 (2018): 14-21. Print.
• Strobl, Susanne, Roland Haubner, and Wolfgang Scheiblechner. "Damascus Steel Inlay on a Sword Blade—Production and Characterization." Key Engineering Materials 742 (2017): 333-40. Print.
• Verhoeven, John D., and Howard F. Clark. "Carbon Diffusion between the Layers in Modern Pattern-Welded Damascus Blades." Materials Characterization 41.5 (1998): 183-91. Print.
• Verhoeven, J. D., and A. H. Pendray. "Origin of the Damask Pattern in Damascus Steel Blades. "Materials Characterization 47.5 (2001): 423-24. Print.
• Wadsworth, Jeffrey. "Archeometallurgy Related to Swords." Materials Characterization 99 (2015): 1-7. Print.
• Wadsworth, Jeffrey, and Oleg D. Sherby. "Response to Verhoeven Comments on Damascus Steel." Materials Characterization 47.2 (2001): 163-65. Print.