The TRUTH about the KATANA, part 3: Why the steel is folded 

I've learned a lot about the katana from Lindebiege, Scholagladiatora, and Skallagrim, but where they've done broad strokes you're really drilling deep. It's good stuff.

Congratulations, you have made a video more informative than every actual documentary I have seen so far on this subject . May the TRUTH bless you with its favors!

This is perhaps the most detailed analysis on this topic I've found. Excellent work! PS I find the sidetracking rather entertaining.

Muramasa was a swordsmith in history. At the end of the Sengoku period the Tokugawa Shogunate made it shameful for samurai to use swords made by Muramasa. Ieyasu Tokugawa feared the swords when one of his son's was killed by one and he was badly wounded by one. Also they were popular among his enemies and essentially stripping them of their swords was one way to eliminate the threat they posed. So, Muramasa wasn't the name of a sword but rather than a smith from the Sengoku era. There was a story that Muramasa and Masamune both met and made a bet to see who could make the best sword. They each took a year to craft their masterpieces. When they met again, they met at a stream and both placed their swords blade facing up the stream. Muramasa's sword was said to cut everything even so much as to draw leaves towards it just to cut them, while Masamune's sword let leaves pass by peacefully. A traveling monk passing by decided to weigh in as a judge and deemed Masamune the winner because Muramasa's sword cut everything without discrimination. Thus the legend of Muramasa swords being bloodthirsty to the point that once drawn they have to draw blood even if it's blood from the owner. Of course the legend of Muramasa was proven to be false since the Muramasa forge in the Ise province went from the late 1400's to the early 1600's while the Masamune forge only ran for a few generations between 1200 and ending in the early 1300's, so their was no link with Masamune and Muramasa, or Masamune with the Tokugawa Shogunate. However; since Masamune even at that time was considered a national treasure for inventing the Sushu technique (7 part distribution of metal composition) Tokugawa's affiliation with Masamune was made up to enhance his reputation. I have a small collection of antique Japanese swords as well as a pair made for my by a winner of the Masamune award. Many collectors of Japanese swords think the Sushu method is the superior method for sword smithing in the way it distributes hagane, kawagane, and shigane within a sword.

You are surprisingly entertaining. That was all I wanted to say.

Historically speaking, dragon fire is what was used to smelt the steel.

He who smelt it, dealt it.

Hey there, Japanese speaker here, just wanted to reassure you that your pronunciation is very good! :) Love your videos

I was impressed that you dissected a scholarly paper to support your presentation, something I've rarely seen on the internet or especially on TV. That is exactly what is needed in debates like this, countering mysticism with hard science. This is a well done series overall. I studied some metallurgy at university and this is at least on par or probably better than many of the lectures I sat through. Thank you for the effort, it must have taken a lot of work!

I really like his excitement about finding an actual research paper :D Great video

15:29 Never heard of Hydrogen Dioxide... But there's plenty of Dihydrogen Monoxide flowing about.

Muramasa was a swordsmith who made many Muramasa blades... many of which (according to legends) were said to contain his hatred, and were said to make the wielders go mad and either kill others, or themselves.

Whoa, you clearly put a lot of time, effort and most likely money towards your channel and it fkn shows. Rarely does one see a new channel just show up out of nowhere with such high quality videos. On a technical level the video and audio quality are superb; the lighting you set up and the set you film in are quite well done and the illustrations to your right fit in really well and are generally of high quality. All that aside you must've put hours over hours into the research for this series of videos alone - quite impressive. If you keep this up, your viewership will increase quite rapidly, I'm sure. As far as I'm concerned this will be the new reference when it comes to katana.

*It is possible to make a sword with "Pig" Iron ( if you don't work out the excess carbon ) .* *The end result is a "Glass sword" .* *Which is really hard and easy to make it ultra sharp .* *But it will shatter if you hit something that is really hard as well .* *~~~~~~~~~~~~~~~~~~~~* *Also Please do a sword ( & other weapons ) techniques ( skills / moves ) series .*

Using and showing a proper published and peered reviewed scientific paper to prouve a point. This is way way too rare on the internet. I would click a thousand times on the thumbs up button if I could. Well done. Sir.

Good video, but you might want to know that the oxides you mentioned were not all stated correctly. They were, in order, silicon dioxide (a.k.a. "silica"), iron/ferrous oxide (a.k.a. common rust), titanium dioxide (a.k.a. "titania"), and aluminum oxide (a.k.a. "alumina"). Aluminum oxide has no "trioxide" nomenclature because the valence electrons only allow for one specific configuration of aluminum and oxygen atoms to form.

"The name of things that are of high quality generally don't have the word 'pig' in them." Except for bacon.

Pig Iron (13.53) Pig iron is the intermediate product of smelting iron ore. It is the molten iron from the blast furnace, which is a large and cylinder-shaped furnace charged with iron ore, coke, and limestone. Charcoal and anthracite have also been used as fuel. Pig iron has a very high carbon content, typically 3.5-4.5%,[1] along with silica and other constituents of dross, which makes it very brittle and not useful directly as a material except for limited applications. The traditional shape of the molds used for pig iron ingots was a branching structure formed in sand, with many individual ingots at right angles[2] to a central channel or runner, resembling a litter of piglets being suckled by a sow. When the metal had cooled and hardened, the smaller ingots (the pigs) were simply broken from the runner (the sow), hence the name pig iron.[3] As pig iron is intended for remelting, the uneven size of the ingots and the inclusion of small amounts of sand caused only insignificant problems considering the ease of casting and handling them. (Wiki)

Shadveristy, I am enjoying this! Really interesting and informative. You were wondering where pig iron gets its name. Perhaps its from the form it was cast into: the bars were called pigs. I can't remeber where I heard this from but it may have been from my father who worked in a foundry.

This was interesting as hell. Thanks for the video. If there are 2 sides that disagree with each other as much as we have with the katana, then the truth will undoubtedly fall somewhere in the middle.

so I assume that these same smelting processes were used making armour? If so that pretty much makes every modern day testing of armour inaccurate. very interesting thank you shad for actual researched information.

13:48 "Pig Iron" (modern pig iron at least) tends to far exceeds the upper limit of carbon for the steel classification. Steel doesn't mean Iron with carbon, but iron with a certain lower and upper limit of carbon per mass in it (though that is a bit of an oversimplification since other elements come into play too in certain steels). Most iron products have carbon in it, hench why most iron products rust. The term pig iron, however, isn't used to classify the make up quality and property of the of the iron, but as a classification of how its produced. The iron ore is rifined to relative high purity and then cast into "chocolate bar-like" ingots, that are then broking into little bits called "pigs". Thus the term pig iron. Pig iron is made with the purpose of being refined further into steels and alloys.

Well done video's, but I have to note that when reading out the study, you are messing up some of the chemical names. A dioxide, is something with 2 (di) oxide atoms bonded to it. FeO, as opposed to SiO2, has only a single oxide atom, and therefore is called Iron-mono-oxide, or for simplicity's sake just ironoxide. The Al2O3 would in the same way be pronounced di-aluminium-tri-oxide. But since it is just the oxidized form of aluminium, we don't bother with that long name, as it normally oxidizes in just that way (it is the most - only? - stable molecule that can form from oxidizing aluminium), and we call it alumiumoxide. The reason they keep talking about Carbon-di-oxide, is because there is specifically a caron-mono-oxide that can naturally form in the oxidation of carbon (CO, the poisonous gas that is released from old malfunctioning heating devises). We keep saying carbon di-oxide because we want to clearly differentiate from the mono-oxide form. In other words, don't call FeO irondioxide, as it is NOT iron-di-oxide. Likewise Al2O3 is NOT aluminium-di-oxide. Just a little heads up on chemical terminology (it is actually quite logical).

Looks at thumbnail. "That is not how you do the Santoryu (santooryuu)." Remembers that Shad does things historically accurate. "Ah, ok then." ... "WAIT A MINUTE!?" Super interesting video.

Pretty cool, I didn't know nearly as much about the making of a Katana, as I do now! But there are a few minor things you might want to know: Silicates and other impurities are not bad in general, when I worked in a metallurgy lab for a while I actually came about a few cases where the lower surface hardness of steel grades with less silicates specifically, lead to failures. In general carbides, silicates (to some extent phosphorus) etc increase hardness, but make the steel more brittle, other metals like tungsten, vanadium chrome and the like all have their own properties in steel. Carbon is only that much more important than the others because it allows the formation of perlite (I don't know the actual english term, but it is Perlit in German :P ) There are steels with tons of non carbon inclusions that are way superior to most carbon steels. Eg. X155CrMoV12 is excellent tool steel with a ton of chromium, X10CrNi18-8 is great spring steel (I heard people love spring steel swords) and X5CrNi18-12 a very tough (though soft) non corrosive steel that would make a suit of armour medieval people would kill for. Tungsten is a different beast all by itself, cemented carbides could literally cut medieval swords in half, I know that, because cutting blades made from WC are used to machine the hardest types of carbon steels Now as of the study you showed, yes, apart from the silicone which makes the sword more bendy and more resistive there is nothing really in there that helps the Katana, but I have the feeling that you kinda created a misleading impression, that most non carbon impurities are bad Also: Hydrogen-Dioxide would be HO2 and doesn't really exist, water is H2O which would be Di-Hydrogen-Monoxide

Very much enjoyed this series, Shad. One of the most informative set of vids about katanas around. Would love to hear you talk about other stuff like berserkers, horse archery or whatever else. Keep up the good work!

I like this series so far Shad. Much like a skilled swordsmith goes through such lengths to remove impurities in the steel he's working with, you went through great lengths to remove any falsehoods in the highly controversial subject of "How good was the Katana?"

Around the middle of the video I believe I heard you refer to H2O as hydrogen dioxide. In fact that would be HO2. What you wanted to say was Dihydrogen Monoxide. Not trying to nitpick, but that seemed important to mention.

this was extremely interesting, i love how you showed your source and those graphs, very enlightening btw in the beginning you accidentally referred to water as hydrogen dioxide, its actually dihydrogen monoxide.

Muramasa was a famous sword maker. And it was told that his katanas were cursed.

+I am Shad Aside from the fact that you tend to repeat stuff a little too much, this is really interesting stuff. It's nice to see someone come at the issue from not just one camp or the other and try to explain it objectively. I have probably seen nearly every documentary on katanas and swords in existence, and there's always clashing information. Once you begin to understand how it's done on a molecular level, though, it slowly begins to make sense. Thanks for this in-depth, detailed video series.

Hey, Shad! Just stumbled upon this video and I am pretty satisfied with both the information you offer and the way you offer it (i.e. you're pretty damn funny). Just one minor thing that bugs me: considering the type of grip and sheathe and the placement of the menuki, the two swords on your left are in the wrong positions. That is, the one below is classified as tachi and therefore should be placed with the cutting edge downwards and the one above is a katana and should be placed with the cutting edge upwards. I know, it's just otaku OCD stuff, but sometimes I can't help it. (no, I don't have an OCD, but don't you sometimes get annoyed by minor things as well?) At any rate, excellent job with the videos, I will certainly watch whatever else you have on your channel. Keep up the great job

Shad I know that likelihood you are actually going to read this comment from this video is small but I guess I wanted to say that pig iron is called pig iron because of peoples descriptions of the European Furnaces. In these old furnaces the molten metal was supplied to a number of moulds simultaneously, this reminded some steel workers of a sow feeding a number of piglets which led to the runner (which carried the metal to the moulds) being called "the Sow" and the moulds it pours into being called "the pigs" [this led to the metal harvested from them being called Pig Iron]. While pig iron's name has nothing to do with its quality it was generally considered a low class product and was made predominately as a cheap high purity source of Iron (~90% iron with 3.5-4.5% Carbon and the remaining ~5% other) that could be remelted and further refined/alloyed as the application called for. Which is why it seems annoying to me that some people would claim that pig iron is bad just because it is pig iron.

Shad seems to fall prey to the common misconception that because "steel is iron and carbon", if you take iron and add carbon to it you'll get steel, or vice versa. That's not really the case and the reality is a bit more confusing. Steel is iron with only about .5-2% carbon. Most iron products (pig iron, sponge iron, cast iron) are about 2-5% carbon. So generally 'iron' has more carbon in it than steel, which is exactly why pig iron isn't steel. You have to actually remove carbon (by melting it down and adding scraps to absorb the carbon) and impurities to turn pig iron into steel. That's also why you can't reduce steel back into iron by removing too much carbon, but you might get minor steel (which is chemically similar but structurally different from wrought iron).

Using oxidation to remove impurities is still done today. When iron ore is melted they pump pure oxygen through it which helps oxidase the impurities and the upwards swelling helps bring them to the surface faster.

Great video. not sure if someone mentioned it already but Muramasa Senji was a famous swordsmith that lived during the Muromachi period

I see this is how they made it. thanks I wanted to know for a while now

I think it's worth noting that pig iron = cast iron.Fully liquefied iron rapidly takes on carbon from the environment and almost always turns into "pig iron" in an open system.Great videos!

The smelting process is a bit deeper than this even. Of note, adding carbon to the iron actually decreases the melting point. So while the smelting process of the day did not get up to 1550C, if enough carbon was added to the ore, it would actually melt, but you'd be left with pig iron, more commonly known as cast iron. This name came from the casting process common in Europe where the molten metal was poured down a channel with numerous ingot molds branching off of it, somewhat resembling a bunch of piglets suckling on a sow. The thing is, steel is just iron. On the low carbon content side, you have what's known as "wrought iron". This is iron which is smelted to a bloom in a bloomery, and then is heated and hammered to get the impurities out. It's relatively soft and easily damaged, but malleable. On the high end of the carbon content, you have cast iron, which is extremely hard, but also brittle. It can't be heated and shaped. Once it's cast, it's done unless you melt it down and recast it. In the middle is what's known as steel. It's harder than wrought iron and holds its shape far better, but can still be heated and reshaped at the forge. The problem? It's a pretty narrow sweet spot to hit between steel and cast iron. Until the mid-1800s, it was pretty tough to get it right due to the inexactness of the materials and tools at hand. So there were many ways developed to reach that spot from baking wrought iron bars in charcoal to the much trickier act of creating a hot, oxygen rich environment to decarbuerize cast iron by drawing the carbon back out, or even forge welding to mix the cast iron with lower carbon iron. Until the industrial revolution and the advent of the blast furnace, making steel was a difficult and time-consuming process, more art than science for the most part, which was one of the reasons it was so valuable.

Just a bit of extra information about Nabegane(鍋がね) and Hochyotestu(包丁鉄) and decarburisation here. Nabegane is called that because nabe means pots and gane means iron/steel and it was used to make pots. Same with houchoutetsu as houchou is kitchen knives, and tetsu is iron as it was used mainly for kitchen knifes. About decarburisation, good Japanese sword smiths and knife makers (and anyone who forges stuff who knows what they are doing as far as I know) try to do all the forging fast to deal with decarburisation. PS: dioxides are when there is O2 in a molecule. FeO is just Iron(II) Oxide or ferrous oxide, Al2O3 is aluminum oxide or alumina, TiO2 is titanium dioxide, SiO2 is silicon dioxide or silica etc. I don't think there is iron dioxide (or very uncommon and only exists in special conditions). PPS: Sorry for all this nitpicking. Your videos explains these things better than any other video that I have seen in English. (Japanese documentary's like the ones from NHK does go a bit more in depth on some parts and there are some written materials out there.)

Wow, that was in-depth. But I could've settled just for the differences between smelting and forging.

If I remember what I've read correctly, the name pig iron actually derives from one of the methods of making it. In some early steel making processes, the production was done in separate stages. In bloomery smelting, you had high enough temperatures to melt some of the impurities out of the iron ore, resulting in a spongey bloom of iron, which would be hammered down into a pig (why it was called a pig at this stage, I have no idea), thus iron at this stage was called pig iron.

Hey Shad. Concerning the name 'pig iron', it came about before the chemical make up of steel was understood. Wrought iron has very little carbon (or none). It's the most pure form of iron generally available in pre-modern world. Pig iron and cast iron have lots of carbon. Steel is in between, but the properties of steel are so different that it got a different name, while the wrought iron and cast iron and pig iron all got lumped together as iron because they seemed more similar to each other than any of them did to steel. It was only when we began to understand the chemistry that the naming started to seem a bit silly.

My understanding of the 'pig' in 'pig iron' is that it was common to pre-smelt mined ore at lower temperatures close to the mine to remove gross impurities prior to transportation to the high-temperature refineries further away. The ingots of crudely-smelted iron were standardised for easy stacking and trassport to be about the weight of a pig carcass.

Well done my friend. It took me a little longer than I thought to watch all 3 due to life, but I thoroughly enjoyed it. I found it extremely educational, and unique in the aspects it focused on regarding metallurgy. I am highly anticipating the next installment. I don't know where you're planning on taking this show as far as topics but I had a suggestion I think would make a great series. So far your discussions on swords have covered categorizing the different types and the construction of the blade, I was thinking you should start going into the different types of fighting styles/methods and the benefits and disadvantages of each and how that changed and evolved the way the different swords were made. Such as the differences between say a rapier and a broadsword and how they were built for certain purposes and attacks. Also maybe getting into the pros and cons of fighting with a shield, I know you already mentioned how just having the shield is beneficial but I mean like getting into dueling using a buckler or an arming sword with a kite shield ect. Just some thoughts I figured you might find useful. Maybe they're things you were already thinking about maybe not I just thought I'd share. Again great job. I have studied the sword most of my life and while I already knew a lot of the things you've talked about your attention on the scientific side, the chemistry is really interesting and taught me a good deal of new information and I commend you for it.

Thank you! Very interesting and informative video. I think it entirely makes sense. However, imho you have made one small error in you reasoning. You are saying that the forging process would burn out slag and only things that already are oxidized would remain. However, you assume that all the components of the slag either produce gas after oxidizing (like carbon) or are already oxidized and therefore cannot be 'burnt away'. You are forgetting however, that there could (and will) be some elements in there that are not oxidized yet but will not 'burn away' when oxidized. Chemical elements that produce solids when oxidized (silicon, titanium, aluminum, iron itself etc.) can be present not only in oxidized but also in pure (not yet oxidized) form at the beginning. They will burn during forging but they will not evaporate like carbon. They will burn and will remain there in the oxidized form after folding process. What I've found interesting in the graphs was that there was significant amount of iron oxide in there. I think you assumed that it was remnant from the iron ore. It's probably true for some part of it but I would imagine that at least some of that would be the result of the forging itself. When hot iron comes in contact with the air part of the iron molecules will burn and oxidize. When folding, you would not be burning only carbon and slag but iron itself as well. Therefore, I think that not only the decreasing carbon content but also the increasing iron oxide content would put some limit to how long you could continue folding process. At some point you would be making it worse by adding more and more iron oxide through forging.

thanks for all your research; it's neat! I am studying enginering and your videos are useful.

a lot of blacksmiths can answer the issues you are not sure about. But you are correct in saying its kinda a mix of both, sure some impurities get folded back in, but a lot of the slag flakes off with the carbon when you upset/distort the metal. good study at the end. now just need a study to see if any of those inclusions detract or enhance the function of a sword.

I think you get several things wrong here, lets back up and look at the metallurgy and how steel is made in modern world. You start with blast furnace, essentially you have a tall furnace, stacked with ore and coke and you pump air in it. The coke burns, iron oxides are reduced to CO2 and Fe, iron settles in the bottom, slag floats on top of that and more coke and ore are continuously poured on top and iron and slag are removed from the bottom. The iron that comes out is indeed pig iron with very high carbon content, because you just melted it in high carbon environment, but the slag is well separated so that is nice. So next the pig iron must be decarburized to make useful steel, that is done in basic oxygen furnace, or earlier with Bessemer process and puddling furnaces. None of these were an option before 18th century so they couldn't make proper steel out of pig iron, therefore it and the blast furnace is out, because you cant properly decarburize pig iron by forging. Now why cant you decarburize pig iron in a forge? You start with 1 part carbon, 20 parts iron(plus impurities) and you want to get 1 parts carbon, 100 parts iron. While carbon is more reactive than iron, guess what are you going to burn more of if you have alloy of 1 part carbon and between 20 and 100 parts iron? You can burn it all away and you won't get it decarburized, you just end up with lots of rust. Instead in Europe a bloomery was used, its essentially same as blast furnace, except its not heated hot enough to melt iron. It could be heated more, its a question of bellows and elbow grease really, but if it were heated hot enough to melt iron it would not be called a bloomery but a blast furnace. Everything else is same, coke, or charcoal, ore and air pumped in. Instead of pig iron you get a bloom out of a bloomery, metal is fused together, but not melted, its porous and full of slag. Its that spongy metal stuff you see in several parts of your video. Iron in the bloom may be full of slag, but it has proper carbon content, unlike pig iron that has little slag but way too much carbon. Unlike pig iron, you can work the bloom in the forge and beat most of the slag out of it and get reasonable quality steel. That's how it was done in Europe and from the looks of it Japanese used pretty much the same process but with hard to pronounce Japanese terminology. Now the process from India is really good and interesting. Its basically crucible steel, but done millennium or two before Europeans started doing it in 18th century. So that is awesome. They get proper carbon content with the bloomery process and they get the low slag content by sticking the bloom in a sealed crucible and melting it in low carbon and oxygen environment. Awesome, best of both worlds. So if you want to know who had best steel in ancient times - the Indians had it. Unfortunately they don't really have an equivalent to "The Way of the Samurai" or "Knight in Shining Armor" to hype up their history.

This answered my Smelting Questions from the last video! The mention of the Quenching reminded me of SmarterEveryDay's videos about the Prince Rupert's Drops. Super hard at the tear, but break the tails, and the whole things explode!

If I remember correctly, it's referred to as "pig iron" because of how it flows from certain styles of smelters. Each smelter has many channels leading to moulds to which the alloy flows and then cools/sets in, and it bears a resemblance to a sow laying on her side with many piglets suckling, the smelter being the sow and the many moulds being piglets.

You messed up the thumbnail! You're supposed to stick the katana handle into your mount. Otherwise, it's a really poor imitation of Roronoha Zoro's 3-sword-style.

Iron is a term given to iron with carbon equivalent above 2%, of it is below 2% it is called steel. What we call cast iron today typically has carbon equivalent of 2-4% pig iron typically has carbon contents of 6-8%. Iron with high carbon contents tend to have lower melting points so while low carbon steel will have melting points around 2700F degrees (to which you would get it to 3000F degrees so the steel would stay liquid longer). High carbon cast iron has a meeting point of around 2200F degrees(to which you would only get it to 2500-2700F to melt it). Tldr: melt processing is complicated and interesting. Source: I'm an engineer that specializes in metal processing, specifically iron products.

I know you might not have a chemical degree. But I just want you to point out that water is H2O or dihydrogenoxide and not hydrogendioxide (HO2) wich is different from water. The naming of the molecules has a system. After each element comes a number, if the molecule has more then one of the same element in it. Then it becomes in the case of H2O dihydrogenoxide. This channel was very informational to me so far and am grateful of that. Keep up the good work.

The folding video is so satisfying to watch.

Dude, these videos are amazing! Grabbed you off of one of Matt Easton's videos and I've kept an eye out and REALLY enjoyed these ones. Looking forward to the next ones!

13:55 The traditional shape of the molds used for pig iron ingots was a branching structure formed in sand, with many individual ingots at right angles to a central channel or runner, resembling a litter of piglets being suckled by a sow. When the metal had cooled and hardened, the smaller ingots (the pigs) were simply broken from the runner (the sow), hence the name pig iron. Should be called piglet steel if anything.

Didn't expect this video to be that good, very clarifying.

15:26 Water isn't "Hydrogen-Dioxide" (HO2), but "Dihydrogen-Monoxide" (H2O). Nitpick over :D

As a physics major, explaining what's actually going on with folding and forging the steel to katana fanboys has been a huge source of frustration. You can't ignore physics, and Shad is right to say that folding the steel doesn't make it stronger, because of the simple fact you have molecules with oxygen bonded to them as a result of harvesting iron ore sand or magnetite. Also, to correct your mispronunciation of the molecules in the study. SiO2 = Silicone dioxide. FeO = Iron oxide. TiO2 = Titanium dioxide. Al2O3 = Aluminium (III) oxide.

For Shad's information, "Muramasa" is a Japanese smith living during the Sengoku period, and his craftsmanship was said to be second to only Masamune. As Muramasa supplied sword to the losing party, when Tokugawa Shogunate ended the warring period, the Shogunate decreed Muramasa's blades to be outlaw, also accused Muramasa's blades of being imbued with witchcraft. However, there are several Muramasa's blades surviving today, as you see in the paper you refer to in this video.

The videos are so long, but I can't stop watching them! At least now I have something long enough to watch during my meals!!!

Excellent videos dude, learned a LOT from them. Waiting impatiently for part 4

There is something missing in his description of smelting. It's not just about "heating iron", because you are heating iron oxide, not iron. The purpose of smelting is a chemical reaction that oxidizes carbon and leaves the actual iron behind.

Hey Shad. just a quick comment about where Pig Iron got it's name. It actually was a simple misinterpretation from ancient Germanic Smiths who would make it accidentally whilst training apprentices and Mistakenly disregard it, assuming they had cooked it too long and caused it to become brittle. The expression "Not even fit for the pigs" was a common saying used to describe something deemed useless. When The Argonians in the Merethic Era discovered references to the material and simply mistranslated it to "Iron For The Pigs." But everything changed when the fire nation attacked.

Muramasa was a legendary sword maker who was known for being violent and mad and for having created beautiful blades which were "blood-thirsty" and cursed and which lead their owner to madness and even death. It is said that a Muramasa blade will refuse to come back into her sheath without having drunk blood. Today, Muramasa blades are still admire and maybe still fear ... This is a very interessting topic, ( and a badass topic ! =D ) a perfect topic for you I think ! =) (sorry for my poor English I'm one of your french viewer ^^)

A small note on the chemical pronunciations, that's not Iron Dioxide. That's Iron Oxide, likewise, it's aluminum oxide. We only use prefixes when we're dealing with molecular formulas.

I really enjoy this series.. would you consider making one of the european forging styles? (i know nothing about it)

In order to produce modern homogeneous steel you have to melt it. Many of the impurities in unrefined iron will burn. The bessemer process and later processes uses this to melt iron, forcing oxygen through semi molten iron to cause the impurities to rapidly burn and heat the iron to melting temperature. This forced smelting was discovered a few times prior to the industrial age, most notably to make wootz(?) steel in India. I think it was even discovered in Japan prior to the Meiji era, but by that time swords were essentially obsolete so there was no motive to apply this to swordmaking.

One important think you forgot to metion - without borax (deoxidizer), you actually increase the content of oxidized iron by repeated folding.

the amount of work for a finished product is greater than just raw materials.

New Zealand also get a lot of it's modern iron from iron sand, and Titanium is a byproduct there too.

I googled Muramasa, he was a swordsmith from the 16th century. Oscar Ratti and Adele Westbrook said that Muramasa "was a most skillful smith but a violent and ill-balanced mind verging on madness, that was supposed to have passed into his blades. They were popularly believed to hunger for blood and to impel their warrior to commit murder or suicide." Cool stuff.

"Oh yeah, my step-dad's really vicious. He keeps trying to bond with everyone."

Wow! Good research there. I realy enjoy looking your video and now got a little understanding of the process. I will watch the other parts later, but cant continue now, cause it would be to much for now.

Great video. Did know alot of this ready. but not all the details and some if the things. always fun to learn something new.

Good Evening Shad, I just wanted to add a few things into this. The way Pig Iron got its name is because it's generally used as a weight, like the in the back part of a forklift, where carbon content doesnt really matter, so its kind of just a mosh pit of impurities and over carbonurization. The reason its called Pig IRON is because of the carbon content. Generally wrought iron is categorized from 0.00% to 0.49% carbon. Soft steel is generally about .5% carbon to 1.3% carbon and high carbon steel like tool steels etc are generally 1.4% to 2.0% carbon. Anything over 2% carbon is called cast iron, and like above when the carbon content doesnt matter with things like weight, itsnjust called pig iron. If anyone wants me go further into some other things about steel and things, leave me a comment and ill be glad to do so as Im currently typing this on my phone. Source: Two years of welding and metallurgy schooling; 5 years as an aerospace and structural steel welder.

shad just a point about japanese steel, they actually do have a tradition of crucible steel, however the crucibles were small because that was all that could be produced mand the carbon content was extremely high like wootz, this steel was used to raise carbon content in the tamahagane stack up when the billet is being forged. however there is also a tradition of imported steels www.naippe.fm.usp.br/hobby/Namban_steel_and_Hizen_swords_latest_fina.pdf heres an article discussing the use of wootz in japanese swords and here www.tokensugita.com/NT.htm is an article discussing antique examples of swords using imported steels in the construction, though this is believed to be dutch cannon steel. further explinationg about japanese crucible steels the japanese crucible steels that were produced, from my understanding only worked due to the high carbon content, from how its been explained to me the higher the carbon content of steel the faster it heats up, and whilst the tatara cant maintain the temperatures needed for very long it can reach them under the right circumstances. basically it needs further research though modern smiths have discussed this with japanese tatara operators and have even tested it.

15:27 Hydrogen Dioxide is HO2, and it's actually called Hydrogen Peroxide. Water is H2O and it's called Di-hydrogen Monoxide. 20:25 Oxygen can bind to things more than once, it's not the number of atoms, it's the number of electrons in the outer shell of the atoms that Oxygen is able to share electrons with to form a covalent bond. Oxygen has 2 electrons in it's outer shell and can fit six more, which is why it can bind to more types of things so easily.

Decarburization is just another word for annealing, this process is countered by work-hardening. Working on either side of that spectrum can do bad things to your steel that is very hard to undo. Sometimes a steel item may have to be repurposed, re-melted, or have to undergo lots of annealing or work hardening. Because of that work sometimes a new tool wad just made and the other was repurposed.

Microscopy is pronounced with four syllables (mi-cro-sco-py), rather than five (mi-cro-os-co-py). Your vids are great to have on and watch while I procrastinate.

iron has a melting point of only 2800 degrees fahrenheit, so perhaps they could first attempt to remove as much impurities as possible and then begin adding carbon, but a lot of these melting points, including your reference of 3000, can easily be inaccurate to the melting point of traditionally harvested iron as the impurities affect the melting point significantly which is why pure iron melts at a lower point than steel.

Mass production of steel was difficult ,getting the correct amount of carbon was a problem so they took it all out and then put it back in later,This was a lot later in the Victorian era thanks to Bessemer converter

When it comes to the smelting process there is one rule that trumps all other arguments: the one who smelt it dealt it.

Thank you Shad! I have various sources concerning the nature and forging of the Katana but this is the most comprehensive by far.

Muramasa is the famed "demonic" sword made by the swordsmith Muramasa. It is almost similar to Dainsleif.

They use charcoal and rice straw to add carbon as part of the sword making process to reduce decarbonisation

You can't remove all of the impurities from iron with any smelting or forging process. The only way to get pure iron is with electrolysis. You can then add whatever carbon you want. Incidentally, iron doesn't rust in its pure form. It requires carbon for that.

Nice video. I know the theory, but having it all put together in a coherent package is quite appreciable. Yet you forgot to mention one process that has been used all around the world (well, maybe not in Japan, can't tell), from the early Iron Age: cementation. And the process is quite simple: once you've folded your steel over and over, and it's as pure and "slag free" as you want it, but also free of carbon, you put your bar/ingot in ashes (as far as I know, it was usually bone or horn ashes, at least in Europe, but don't take my word on it), and just heat it up for hours, or even several days. The lack of oxygen and the presence of surrounding carbon, will allow the carbon to migrate inside the steel, sometimes quite deep. You have to be carefull not too alter the steel by going too hot, but otherwise it's a pretty secure process, and there is not much chance to mess it up. It can be done either on "raw" bars/ingots, or on the semi-finished sword blade. The advantage if you use this method on a semi finished blade surrounded by ashes on all dies is that the acute edge will heat up fast and, as it's thin, take much carbon, the sides and spine of the blade will take a bit less carbon, and carbon won't be able to migrate deep enough to the core. In other words: it will make the edge quite hard, the sides and spine moderatly hard, and leave the core mild. And all this on "superior", "slag free" steel (well the best available from a bloomery). As far as I know, carburizing was massively used in Europe in the late Middle Age and early Modern period, because blast furnaces weren't widespread (as it requires much more material and workforce to make it run, and requires investments - not all social structures had that mindset), but bloomeries were quite common, and there was a real need for high quality steel. Folding pig iron was necessary to get rid of the slag, but they ended up with "high purity" (for the time standards) wrought iron. This process was made easier and more efficient by the use of water powered trip hammers. They forged the wrought iron in long, thin and narrow bars, bundled them together in a" plate" or sheet, pilled in alterning layers with ashes/charcoal (any carbon-rich substance), and let it heat up the adequate duration. The result is blister steel, inheriting the high purity of wrought iron, but now with a high carbon content. It was then forged back together and folded to even the carbon content and lower it a bit, producing shear steel, which was in every way superior to tamahagane. The difference is the use of cementation, and water-powered trip hammers to make the forging job easier. And also a pre-industrial production context for efficiency, which cannot be achieved in traditionnal two or three men shops. This is just bits of extra information. Your video is already excellent!

That red katana on the wall is absolutely gorgeous. I'd love to have one just like it and I'm not even a big fan of katanas.

Recently watched this, so stopping back on by to leave a like a comment.

17:44 I am not a chemist, but I'm pretty sure that silicates (which are basically rock) don't burn. And even if they did, the end result would likely be silicon dioxide, AKA quartz, which would still be an impurity. Also, as others have already hinted at, pig iron is not a type of steel; there is an upper limit of how much carbon can be in steel for it to still be steel, and pig iron contains significantly more carbon than that.

I believe the reason they call pig "steel" pig iron is because steel was originally called Good Iron, I'm not sure when the term steel came about, but some sources I'd read say about the time of the industrial revolution around the time some bright spark figured out how to mass produce (good iron) steel.

The e in japanese hasn't got the "ei" sound you tend to use. It more like the e sound in "meh".

I may be wrong as I don't remember much from my chemistry class but in the process of making the Katana couldn't some of the TiO's oxygen bonds be broken leaving Titanium metal spread evenly throughout the Katana in the end product after quenching, making it stronger?

I'm not really good at chemistry, but I think I'm good enough to comment on inorganic chemistry. Most stuffs occurred naturally are oxidized because oxygen is very aggressive. Very few elements can stay pure, like gold. Even coal is actually a chain of hydrocarbons with tons of impurities like sulfur, phosphorus, and even radioactive elements like uranium, as coal are fossils of dead animals and plants trapped in freshwater underground, similar to oil (which are fossils of dead animals and plants trapped in salt water). Iron ores are the same, and as you said before, they are rust. Rust are not good to make stuffs, and melting iron even at 1,600-2,000 degrees Celsius is not enough to take oxygen atoms away from that oxide (burning iron actually oxidizes iron). However, the thing is, the process of smelting provides the temperature that carbon (mixed in the ores) and carbon monoxide (by-product of burning fuel while lacking oxygen) that will take oxygen away from the iron ores. This process is called reduction and it allows you to get the element iron instead of having a sword made from rust. You can also use this reduction method to get copper and many common metals in history. This is also the reason why aluminum took a long time for human to proceed. The oxide melts at much higher temperature (over 2,000 instead of 660 of regular aluminum), and you cannot reduce aluminum oxide as the element is much more active than your regular metal, so active that it can form a layer of oxide at the surface to protect itself from being oxidized further. Even with modern technology it is more efficient to just recycle aluminum than smelting it from ores. Back to the topic, the forging process (with folding), however, will not be able to take away the solid impurities, like silicate, carbonate compounds or many oxides of active metals, since they cannot be burnt or reduced, have high melting point (Titanium dioxide at over 1,800 and aluminum oxide at over 2,000) thus stay solid, while other elements, if exist, like carbon or sulfur, can be burnt and become wasted gas as their oxides are gaseous. If you have ton of silicates in the ores it is likely that your final products will still have silicates in it. Same to TiO2 or Al2O3. Folding does help in reducing iron oxides into pure iron however as the inferior smelting technique likely does not allow carbon to reduce the oxides.

Although Im no fan of katana (mostly because of the fanboys) but I enjoyed your video very much. Very impressive research and very well done presentation of the facts. Well done and thank you.

The thing with the three kinds of steel only holds true for a very small percentage of swords, though. Making the edge and sides out of Nabegame (which has a higher carbon content than normal, making it both harder and more brittle) is *hard*. Must blades just made do with a soft spine inlaid in a sort-of-v-shaped outer layer of harder steel. The blade is hardened afterwards anyways.

okay,but gotta remember where the ore for the swords are found. Also one study on one blade does not prove that all blades are like that. It's also not stated who the sword was originally made for. Muramasa made swords all over the place from tones of different ores. A blade made for a foot soldier would be infer to that of a true Samurai or shogun's. His techniques are also considered infer to other great swordsmiths. You also have to take in the age of the blade,how many battles it's seen,the amount of times it's been repaired,and how many owners it's been with. This goes for any sword regardless of origin.

15:24 actually water is dihydrogen monoxide, not hydrogen dioxide 🙂