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Damascus steel's lost secret found
By Jeremy Manier
Tribune staff reporter
August 13, 2001
For hundreds of years, some of the keenest minds in science sought in vain to tap the secret of how blacksmiths in ancient India and the Middle East fashioned a supremely tough metal known as Damascus steel.
Legend had it that the metal, stronger and sharper than some steels produced even in industrial times, may have helped Islamic armies repel European crusaders with inferior weapons during the Middle Ages.
The search for the shimmering alloy may now be at an end, thanks to an unlikely alliance between a materials science professor at Iowa State University and a Florida blacksmith who crafts shoes for racehorses.
Their apparent recovery of the lost technology just might aid modern steelmakers in the hunt for new steels to make lighter automobiles and tougher engine components, experts said.
The work already has revealed much about the original Damascus steel, prized for its distinctive wavy surface that Persian poets likened to ant tracks or rippling water. Islamic artisans used it for centuries to make swords that spurred envy and myths among Europeans--including the legend that a Damascus blade could slice a falling silk scarf in midair.
But finding what some experts call the Holy Grail of metallurgy took the professor and the blacksmith on a quest that spanned decades. Some of the keys to forging the stubborn metal now appear tantalizingly simple, such as a trace impurity that proved crucial after the team ignored it for years.
"If you just keep at something like this, beating your brains out, eventually you can figure it out," said John Verhoeven, the Iowa State professor. "But it took us an embarrassingly long time to do it."
Cracking the puzzle brought the unaccustomed title of scientific pioneer for Al Pendray, the blacksmith who is a former rodeo wrangler.
"A lot of people said it's rare that a so-called country blacksmith could sit down and work with a top metallurgist," Pendray said. "The two of us together got to the answer."
Controversy has tempered their triumph, in the form of a running feud with researchers at Stanford University who believe they re-created the old metal using modern rolling mill techniques.
Yet even their rivals concede Verhoeven and Pendray are the first to recapture both the external beauty and microscopic structure of genuine Damascus blades.
"This technology has been lost for about 200 years," said Ben Bronson, curator of Asian anthropology at the Field Museum of Natural History in Chicago and an expert on Damascus steel. "A real driving force in the development of modern steels was the attempt to replicate ancient Indian and Middle Eastern steels."
Steel not made in Damascus
Early descriptions of the metal date at least to the 1500s, but many scholars believe Muslims from Egypt to India used it for hundreds of years before that. Western traders encountered the steel in the Syrian capital of Damascus, though there is no evidence it was ever made there.
The silk scarf legend comes from the 19th Century English writer Sir Walter Scott, whose fictional tale of the Crusades described the Islamic army's swords as being "of a dull blue color, marked with ten millions of meandering lines." The hallmark pattern became known as damask, or damascene.
Europeans' interest in copying the steel grew around 1800, just as the art of making it was vanishing in the Islamic world.
The original artisans did not leave complete instructions for making their steel, and the few written formulas are less than helpful. Some advise quenching the red-hot blade in the urine of a red-haired boy or of a goat fed nothing but ferns. Another text suggests driving the sword into the belly of a muscular slave.
Chemical tests in the last century began to reveal the swords' composition but only deepened the puzzle of their manufacture. The enigma of Damascus steel boils down to finding a way of making steel that is high in carbon but not so brittle as to be useless.
Verhoeven began testing techniques in the early 1980s, still beguiled by a mystery he had stumbled across as a student decades earlier. But after years of trying to do the job with a modern rolling mill, he decided that a key might be forming the metal by hand, with a hammer.
Before long, Verhoeven had found Pendray--a blacksmith who had also taken an interest in weapons--and the two men were launched on their mission.
While Verhoeven schooled Pendray on experimental methods and had him read advanced metallurgical texts, the blacksmith gave the professor a tutorial in the art of steel forging.
"Sometimes I'd have to tell him, `I don't care if you've got a PhD, you don't understand what the hell's going on here,'" Pendray said.
To make the steel, the men used ingredients resembling a witch's brew--glass chips, iron, oyster shells, green leaves and charcoal for carbon.
The work went slowly. They spent a year just figuring out how to keep carbon in the steel ingots from coalescing into graphite, which always robbed the finished product of its strength and surface markings.
The solution? "You heat it up really hot and beat on it really hard," Verhoeven said.
In time, Pendray hit upon a method involving dozens of heating cycles, which would occasionally yield the right external pattern and the microscopic hallmarks of genuine Damascus. But many batches failed, and the men had no idea why.
"We were stumped," Pendray said. "What did we do right? It would make you want to tear your hair out."
Overlooked in their reckoning was an element called vanadium, which made up just .003 percent of some iron the team used.
Verhoeven now believes the steel's markings arise from patchy layers of vanadium that form as the metal cools and hardens. Further heating cycles fill those bands with hard, carbon-rich steel, surrounded by a softer, springier material.
Hard but not brittle
That combination, experts said, gives Damascus steel its lasting sharp edge and makes the metal hard but not brittle.
Although Verhoeven and Pendray have patented their technique and received some funding from Nucor Steel Inc., they concede the technology in its current, labor-intensive form probably is not a moneymaker.
Their Stanford rivals got closer to finding applications for their version of the metal, including a partnership in the early 1990s with Caterpillar Inc. of Peoria. They still hope that their high-carbon material, which they call "superplastic steel," could allow makers of vehicles such as airplanes to replace riveted sheets with fewer, stronger parts.
The long quest has left Verhoeven and Pendray with a newfound sense of connection to the ancient craftsmen who made the steel for great armies.
Copyright (c) 2001, Chicago Tribune