Magic Swords: How Real Blacksmiths Inspired the Fictional Blades of Legend

Appears In:

• King Arthur and the Knights of the Round Table: Excalibur
  
• Lord of the Rings: Narsil, Anduril, and Sting
• Game of Thrones: Valaryan Steel Swords
• The Legend of Zelda: The Master Sword
• Harry Potter:  Gryffindor's Sword
  

One thing that movies get wrong about real life swords is that they used to break constantly. Imagine for a moment that you are a knight fighting in your king's militia. By your side you carry your trusty sword--it's the third sword you've had since the campaign began, but it's lasted longer than the ones before it. In the distance you see an enemy knight tearing a path across the battlefield. Every swordsman who dares cross blades with the knight is swiftly left holding a hilt with a shattered stub where his sword once was, if he's lucky enough to be capable of holding anything at all. That knight's sword must be magic! Is it blessed by divine providence? Maybe. Is it made of rare ores from a far off mountain? Probably. Was it forged through arcane methods by a wizard blacksmith? Definitely.

Since the dawn of the Iron Age, around 1200 BCE, steel has been the material of choice for swords and other weapons, but not all steel is created equal. Subtle differences in the process used to forge steel can result in massive differences in how the material behaves, so over time the best steel-making processes became closely guarded secret rituals, and the cultures that produced fine steel became the stuff of legend. For centuries the best steel in the world was produced in Damascus, Persia. Those legendary Damascus Steel blades were the strongest, the sharpest, and they shimmered with a pattern that looked like swirling eddies in a river. However, ultimately the secrecy of the Damascus steel ritual became its downfall when a generation of trade disruptions resulted in a lack of quality iron getting to Damascus, so with no iron to work the knowledge of how to make this legendary steel was lost to time for many years. 

 17th Century Persian Shamshir made of Damascus Steel, courtesy of the Met Museum

The reputation of Damascus Steel lived on, however, because the blades that had already been forged continued to outperform their newer counterparts even after becoming antiques. This story of ancient legendary blades that were forged using forgotten secret methods has been borrowed for use in countless fantasy stories over the years. Valaryan Steel in the Game of Thrones franchise echoes the story of Damascus Steel almost exactly, where the unbreakable relics of an enlightened ancient civilization have mystical properties that can't be replicated using modern methods. Damascus Steel and other fine steel swords also often became heirlooms due to their years of stalwart service, causing them to be thought of as blessed by divinity or by the valor of their original wielder. This trope of blessed heirloom swords is echoed across countless fantasy stories like King Arthur, Lord of the Rings, and Harry Potter. Lord of the Rings in particular demonstrates both tropes, because all of the named swords owe their quality to the elves' secret blacksmithing methods, and Aragorn's sword Anduril has the additional reputation of having been wielded by multiple kings.

Although Damascus was particularly renowned for their steel, high quality steel was produced at least sometimes by practically every iron-working culture in the world, because the process of making steel is so simple that it's possible to make legendary quality steel by accident. Once the iron ore has been melted and separated from other rocks and debris (called slag), all it takes to make steel is to take the melted iron and mix it with a little bit of carbon from charcoal. Since less than a 1% inclusion of carbon is needed to turn iron into steel, and iron was historically heated using charcoal fires, practically every iron product in history has actually been made of steel due to minor carbon "contamination." However, just because the process is simple doesn't mean it's easy. Iron melts around 2800F (1500C), so producing a fire hot enough to melt iron, and a furnace that can withstand that level of heat every day is no easy task. On top of that, the amount of carbon has such a potent effect on steel quality that a difference of as little as 0.1% in the amount of charcoal mixed into the iron can mean the difference between a sword shattering on the battlefield or not. All of this means that a clumsy blacksmith who accidentally dropped his hot iron on the coals might have inadvertently added the perfect amount of carbon to turn an otherwise fragile sword into the next Excalibur, and no one would know until that sword has proven its might on the battlefield. 

In movies, scenes that involve blacksmithing also often focus on the final cooling step, where the red-hot blade is quenched in a bubbling trough, usually emerging from its bath in a tempest of smoke and fire. This cooling step is true to real life and has a huge effect on the quality of the finished sword. Modern blacksmiths usually quench swords into warm oil, because it allows the blade to cool relatively slowly and evenly. When the oil-soaked sword is removed from the bath, the residual heat on the metal often causes the oil to catch fire, just like in the movies. However, in both fiction and in historical blacksmithing, swords have been quenched in everything from water, to oil, to the blood of the enemy. Although oil is generally the most effective choice for a quenching bath, the image of a sword metaphorically "drinking" the liquid it is quenched in can make for some irresistible symbolism about how that sword will go on to be used. For example, the Harry Potter series uses this imagery for a major plot point where Gryffindor's Sword takes on venomous qualities after absorbing the power of a basilisk it was stabbed into.

Swords are a particularly good example of the skill that goes into blacksmithing, because to excel on the battlefield a sword needs to strike a difficult balance between seemingly contradictory properties. Swords must be strong and light, sharp and flexible, durable and easy to mass produce. The lessons humanity has learned while refining steel for weapons continue to be used for everything from armor to tools and construction materials. Everything mentioned here about the steel-making process is just as true for the tools of peace as they are for the weapons of war, because just as a sword can be used for a multiplicity of purposes, so too can the steel it is forged from.

-------If You're Curious-------

After seeing how influential Damascus Steel has been in fiction, it naturally begs the question of "What makes Damascus Steel so special?" Aside from its striking appearance, Damascus Steel also elegantly finds a way around some of steel's natural limitations. We can generally think about steel in two types: steel with lots of carbon in it (often called "carbon steel" or "hardened steel") and steel with just a little bit of carbon in it (often called "cast iron" or "wrought iron"). High carbon steel has the benefits of being extremely hard and holding a sharpened edge well, even after repeated uses. However, this hard steel is also very brittle, so if the steel takes a large impact, it will chip and shatter rather than bending. Low carbon steel has the benefit of being softer, which makes it easier to shape, and the benefit of bending when it is struck, rather than breaking. This softness makes low carbon steel bad for knives and swords, because even if the blade is made razor sharp, the thin edge will squash into dulling itself as soon as the blade is pushed into a surface.

For a sword, ideally one would want the best aspects of both kinds of steel: razor sharp and ability to bend slightly when it parries an attack or clatters against armor, rather than shattering, since a bent sword is still usable and a shattered sword is not. Using steel with a medium amount of carbon in it might be the natural choice, but this would result in medium properties as well--an edge that will hold for only a few cuts, and still being fairly prone to shattering. Damascus Steel solves this compromise using a much more clever approach. During the forging process, slim pieces of steel are stacked up in an alternating pattern of high carbon and low carbon steel. This steel stack is then heated enough to soften the steel and stick the layers together, but not so hot that the layers mix with each other. The soft taffy-like stack is then folded in half, squashed flat with a hammer, then folded again, repeatedly until the pieces of high and low carbon steel become thousands of extremely thin bands. This process is very similar to how layers of bread dough and butter are folded and pounded repeatedly to make puff pastry. Since low carbon steel is darker gray than high carbon steel, the layers in the resulting blade are clearly visible, and artisans took advantage of this by using all sorts of clever folding patterns to produce beautiful designs in their blades. The Damascus Steel blade that results from this process has enough soft low carbon steel in it for the sword to bend rather than breaking, and the alternating layers mean that by shaving off the blade's dulled edge through sharpening, there is always a new layer of hard high carbon steel ready to be made into a razor's edge. 

Japanese katanas are made in a similar way to Damascus Steel and carry many of the same benefits. They also involve folding layers of hard and soft steel, although generally with fewer folds than Damascus Steel, and katanas have the added cleverness of placing most of the hard steel at the cutting edge of the blade and most of the soft steel at the supportive back of the blade. This produces a blade that is much easier and faster to produce than a Damascus Steel blade, while performing just as well.

In the modern era, one can buy brand new Damascus Steel knives for high prices. Skilled blacksmiths make the genuine article by folding together two types of steel dozens or hundreds of times, and unfortunately these works of art are often sold right next to fake "Damascus Steel" that is actually just a single type of steel that is painted or etched to look like it has the Damascus pattern. For the typical user, there is no functional benefit to using Damascus Steel knives over regular high carbon hardened steel knives, because people don't generally need their kitchen knives to bend. Most moderate quality kitchen knives are made of hardened steel that can be sharpened to a razor edge if they are cared for properly, and those knives can hold that edge for a very long time. If one were to take a modern kitchen knife into battle and thrust it into an armored combatant, the knife would shatter and become useless, but that is not a functionality that most people need out of their knives, so today Damascus Steel is more about artistry than utility. 

-------The Nitty Gritty-------

So why does carbon strengthen steel? And why does cooling matter so much? On a microscopic level, metals like steel are made of tiny pieces called "grains," named that because they look like thousands of grains of sand all glued together. The metal grains are held together through metallic bonding in a manner very similar to magnets sticking together. Just like with magnets, grains that are stuck to each other can slide across each other relatively easily, but it is hard to pull them apart. This is why metal is malleable, it can be bent relatively easily, but it is not easy to pull it until it snaps like a piece of string. When metal is bent, the grains all slide along each other to settle into a new shape once the bending is over. However, some metals are easier to bend than others.

In the magnet metaphor, imagine that instead of the magnet surfaces being smooth, they are instead very rough or even jagged. Depending on how rough the magnets are, it might still be easier to slide them along each other than it is to pull them apart, but sliding them is much harder than when they were smooth. This is the role of carbon in steel. Carbon adds roughness into the boundaries between iron grains and causes the grains to resist sliding against each other. This means that the more carbon is in the steel, the more it resists bending, since the grains can no longer slide along each other freely. This extra stiffness also means that the steel's hardened edge will cut into softer surfaces, rather than bending out of the way. However, at very high carbon contents, the grain boundaries become so resistant to sliding that when force is applied, the grain boundaries will crack apart rather than sliding into a new position. This is why high carbon steel is hard, but brittle.

Cooling rate also plays an important role in the grain boundary puzzle. Before red-hot steel is placed into a cooling bath, it is molten on a microscopic level and no grains have formed yet. As the steel cools, it solidifies into separate grains, much like individual spots of frost forming on a wet window on a cold day. If the steel is cooled quickly, countless tiny grains form across the material all at once. If the steel is cooled slowly, then a few grains form initially, and those grains grow slowly as they cool. Theoretically if a piece of steel were cooled slowly and evenly enough, then the entire piece could become one giant grain, although this doesn't happen in practical settings. These different cooling treatments can result in steel with vastly different properties. More grains means more grain boundaries to slide around, which results in a very flexible final product, even if a relatively high amount of carbon is used. Paper clips are one common example of fast-cooled steel, and as such they are very flexible, but not particularly strong. Steel that is cooled very slowly and has very few grains has the opposite properties, because with hardly any grain boundaries to slide around, slow-cooled steel is very stiff. Drill bits are often made of this kind of steel, making them hard enough to cut into all sorts of surfaces, but also making them prone to snapping rather than bending if too much pressure is applied to the drill. 

Both carbon content and cooling rate have huge effects on the strength, flexibility, and stiffness of steel, so both must be controlled and balanced very carefully to produce steel with the precise desired properties. Thanks to the efforts of thousands of blacksmiths over thousands of years, humanity has come to understand this delicate balance well enough to reliably produce steel that is so cheap and accessible that we trim our nails with it, and so strong that we trust it to hold up our homes without a second thought. This arcane knowledge that has been passed down and refined over countless generations has become so commonplace that we take it for granted. In many ways we live in a fantasy world already, where modern tradespeople perform daily miracles that would be the stuff of legend, if only our ancestors had the opportunity to witness them.

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