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The Iron Throne and Steel Swords: GoT for Engineers

The Iron Throne

This is the second article in our exploration of the material world of A Song of Ice and Fire, more familiar to us as the Game of Thrones. You can read the first article in this series here.

The direwolf, the kraken, the falcon, the stag, the lion, the rose and the trout – were no match for the three dragons that came from the east. One by one, they knelt before their new king and his sister wives. Those who did not, paid with their lives and honour. The arrogant king of the Ironborn who hid in Harrenhal was baked alive when the walls turned red hot with the breath of the Black Dread. Even today, in a quiet moonlit night, the wail of the king and his sons can be heard, their charred bodies moving against the melted stone.

The dragons were three:

  • Vhagar was the smallest, but her fire could melt armour.
  • Meraxes with silver scales could swallow a whole horse.
  • Then there was Balerion, the Black Dread, whose shadow covered whole villages and cast terror even into the hearts of the knights.

After Aegon the Conqueror became the ruler of all men to the west of the narrow sea, he commanded his general, Orys of House Baratheon, to bring a thousand swords of his enemies to his new capital, the Red Keep. There the breath of Balerion forged them into the seat of ultimate power in Westeros, the Iron Throne.

The throne as conceived by the HBO series hardly has over two hundred swords. According to the series creator, George R R Martin, the version of the throne that best fit with what he had in mind was conceived by the concept artist Marc Simonetti. This towering monstrosity, shown in the image below, captures how one thousand swords could be arranged into something resembling a throne that could be fused by fire.

The Iron Throne as conceived by Marc Simonetti
Fig. 1: The Iron Throne as conceived by Marc Simonetti [1].

The throne as conceived by the HBO series hardly has over two hundred swords. According to the series creator, George R R Martin, the version of the throne that best fit with what he had in mind was conceived by the concept artist Marc Simonetti. This towering monstrosity, shown in the image above, captures how one thousand swords could be arranged into something resembling a throne that could be fused by fire.

While conveying a true sense of authority, this gargantuan beast is clearly too cumbersome and expensive for a film set, which could be why HBO opted for the tamer version seen here:

The iron planet

While a mundane material in today’s world, iron was held in very high esteem throughout much of our history. The only pure iron found on Earth came from meteorites that fell from the sky and somehow managed to stay preserved until discovery. This ‘celestial‘ iron was much valued in antiquity. An iron dagger made from meteoritic steel was found with the mummy of the Egyptian Pharaoh, Tutankhamun, dating to 1300 BC. In fact, only around a hundred or so iron artifacts have been found that predate the beginning of the Iron Age (roughly 1000 BC).

Ironically, Earth is an iron planet. Roughly 32 % of the Earth is iron by mass. The outer core of the Earth is a swirling ocean of liquid iron while the inner core is a solid sphere of crystalline iron.

Iron Ore
Fig 3: Iron ores are rocks and minerals from which metallic iron is extracted. The ores are usually rich in iron oxides and can be dark grey, bright yellow, or deep purple to rusty red.

On the surface, the polyamorous element is found most often in combination with oxygen or silicon. However, iron smelting – the separation of pure iron from these ores – requires very high temperatures exceeding 1500 °C. By comparison, copper melts at 1084 °C and bronze at 950 °C. Without a specialized kiln, the extraction of iron on an industrial scale was a significant technological challenge that was solved only during the eighteenth and nineteenth centuries.

Carbon, iron and their dense chemistry

Iron metallurgy is theoretically simple: remove oxygen from iron oxide to get pure iron. Oxygen is removed through the addition of carbon, which may come from wood, charcoal, coke or whatever material is used to fire the furnace. However, the tiny carbon atoms also easily squeeze themselves into the microstructure of iron – especially at high temperatures, such as those found inside a kiln.

The result is that early metallurgical iron had a high carbon content. Worse, until a few hundred years ago, no one knew enough chemistry to see what was going on, so that the amount of carbon was highly variable depending on the type of ore, type of fuel, nature of the kiln, place of extraction, humidity, etc.

This was a big problem because, much like salt in water, a tiny amount of carbon can drastically change the nature of the resulting iron.

Pure iron is a relatively soft material that is malleable and ductile. Knives, swords and agricultural implements made of this material deform easily and are practically useless.

One way to improve the performance of this material is to hammer it repeatedly after extraction. Such worked (or wrought) iron is much tougher and, before the advent of steel, used to be the material of choice to build warships and railway lines.

A high amount of carbon – in excess of 2 % – makes iron very tough. These knives and swords don’t flex at all. However, they are brittle and shatter upon impact much like a white walker on dragon glass. They are useful wherever high-strength impacts are not expected such as in building park benches, garden furniture, etc. This kind of iron is easy to mould or cast and hence is called cast iron.

The properties of iron change drastically depending on the carbon content. Steel has between 0.08 % and 2 % carbon.
Fig. 4: The properties of iron change drastically depending on the carbon content. Steel has between 0.08 % and 2 % carbon.

Steel is iron with a carbon content between both of these extremes. When the carbon content is less than 2 %, carbon atoms find themselves snug in corners within the unit cell of iron, resulting in a uniform microstructure with strength and flexibility. Today, it is the most common construction material in the world produced in excess of one billion tons every year.

The iron that does not rust

Perhaps the most famous property of iron is that it rusts. Chemically, rust is a hydrated oxide of iron formed by the action of oxygen. Most metals form oxides; the trouble with iron oxide is that it occupies more volume than pure iron, causing it to expand like heated popcorn and flake away. Over time, iron can disappear entirely like some blight infested wheat.

The variety of steel called ‘stainless steel’ overcomes this problem by the addition of a generous amount of chromium (around 11 %). When exposed to air, chromium turns into a transparent coating of chromium oxide that sticks to the surface of the iron. This inert layer protects the underlying metal from further corrosion.

Rust-free iron has been known even in antiquity, though often through accidental discoveries that never allowed it to catch on in a major way.

A great example is the Iron Pillar in Delhi, India. 7.2 meters high, 41 centimetres in diameter and weighing over 6,000 kg, this pillar has been standing since at least 400 AD. No one knows the exact time when it was commissioned so the pillar could be even older than this.

The magic ingredient in the Iron Pillar is phosphorus, which causes the formation of a passive layer of hydrogen phosphate hydrate, preventing further corrosion. The Iron Pillar, like the Iron Throne, was made by heating together different pieces of wrought iron and beating them into a single material, a process called forge welding.

The Iron Pillar at the Qutub complex, Delhi.
Fig.6: The Iron Pillar at the Qutub complex, Delhi.

Dragon fire

Iron is a tough metal to work with, especially if it is to be forged or fused; requiring high temperatures and intense labour. The origin of the Iron Throne, therefore, gives us a rather interesting insight into the properties of dragonfire. To melt the iron swords, Balerion’s fire breath must have been over 1300 °C in temperature!

The lore of GoT has it that dragonfire is the result of the coming together of two different chemicals ejected from separate tubes in the dragon’s mouth. The chemicals by themselves are harmless but combined they are an explosive mix resulting in iron-melting fire.

It’s too bad that we don’t have this fire here on Earth, or the dragons that produce them. However, heat and iron have joined together in the past to create equally lethal weapons of destruction. The swords of medieval Europe, the near east, India, China and Japan have together claimed thousands and thousands of lives in battles large and small.

These swords were at the time believed to have been made not just of iron but also of magic. Today, with scientific understanding, we can see that they were indeed made of magic, but the magic of precisely controlled microstructure and human inventiveness.

We shall explore these lethal steels in the next article.

I work in the cutting edge area of applying machine learning and artificial intelligence to one of the earliest endeavours of human civilization - in understanding, exploiting and developing new materials.

*This article is the work of the guest author shown above. The guest author is solely responsible for the accuracy and the legality of their content. The content of the article and the views expressed therein are solely those of this author and do not reflect the views of Matmatch or of any present or past employers, academic institutions, professional societies, or organizations the author is currently or was previously affiliated with.

* These images were taken from Game of Thrones, or from websites created and owned by HBO, the copyright of which is held by HBO. Images are used for educational purposes only. 

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