HOW FLEXIBLE and Hard Were Medieval (and other) SWORDS? 

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Watching Matt madly step on the brakes to avoid saying "[...] there is a Shitload of evidence" at 16:44 was a highlight of the video lmao

Thank you from the video - I just want to throw some science in it. From a micro structural point of view, you need a uniform tempered martensite structure to obtain extreme flexibility (bending the steel ina U shape withour plastic deformation) and tbh only modern technology brought us this far, since period swords were not uniform to that extent (you will always find places in which the blade is not uniform but softer/harder and that could lead to a failure). And if we look at the literature of sword analyzed in that microscopic way, only a handful present such structure, hence why the statement of Ilya I believe is correct, purely from that sample (which as you can immagine is not larger). Eventually all hardened steel can take some elastic deformation (returning to true) and "spring back" to some extent although much of this has to do with cross section and stiffness of the blade (a katana is just thicker and stout, so you will need much more force to obtain the flex you see in this video - the same amount of force that can cause a longsword to take a set for example). The degree of flex in historical swords is also related to edge hardnes and period. Uniform tempered martensite period tend to have softer edges compared to layered/piled ones that cannot have a tempered martensite core (too little carbon to be hardened). These blades can still take some degree of force and have elastic deformation, skallagrim recently tested some differential hardening blades and you can see the flex during the cut footage. The difference lies in the yielding point in which plastic deformation happens and the amount of force required to create such yield.

Always funny to me when people call modern epees unrealistically floppy car antennae. Even ignoring how much stiffer they are compared to historical foils used for smallsword training, I've had jackets torn by an epee that broke at the tip. People have died from them. People vastly overestimate how stiff a sharp bit of metal needs to be to be dangerous.

A point of metallergy: Excluding mostly modern high alloy steels, the temperature of quench to harden doesn't vary for how hard you want the steel, being based on the same crystalline phase transition. The carbon content has some influence on pre-quench heat. The carbon and alloy content, and speed of quench (oil vs. water, thickness of material) impacts how hard the steel gets. Following the quench a blade is usually tempered, heated to a lesser temperature allowing the metal to relax some, which makes the steel softer but tougher. Temperature, time, and alloy all influence how much the temper softens the steel.

A few additions: It is almost never shown, but Japanese swords are tempered above the fire after quenching (so low temperature tempering). Metals are all crystalline. The phase is different: edge (hamon) is martensite, back is ferrite, in between is a mixture of martensite, bainite, and ferrite.

Thank you for all the information, very useful indeed.

Hi Matt! Thank you for bringing on this topic. I have dedicated a lot of years reading the literature (mainly works of A.Williams and related, but also other Japanese related papers) and while to some extent I agree with you, I think I am not fully aligned here. The problem is that this topic is approached in very black and white terms and it is more nuanced than that. Every swords (or piece of hardened steel, to some extent) will flex and return to true, having an elastic deformation. Be it a katana, a dha, longsword and so on. The crucial issue here is the force applied and how far is the yielding point with such items, and it is not entirely related to the microstructure (the temper), but also to the thickness and cross section of the blade. Skallagrim tested multiple times differentially hardened blades and you can see the cutting footage of those blades flexing and bending while returning to true. There is also a destructive test on a modern made Katana made by Taro Asano and he did perform a bending test with his blade - it got bent over 45° once and returned to a bend angle of around 10-15°, so they do have a significant stress margin considering that the force applied to bend such thick blade to that extent is much higher to what you will apply to a thinner cross section (which as you said, flex under their own weight). So it is much more nuanced than "oh katana bends and stay bend, European swords flex" because both swords do bend and flex, but the forces required to achieve deformation are different and so are the yielding point. Moreover, a flexible structure is not that desirable in a thrusting implement, you want a stiff structure to direct the force - I get what you mean by being desirable, but you want a stiff cross section that allow very little deformation in the first place. Concerning the medieval term here, I do not agree that the majority of blades were spring tempered. They might have been in the late 16th century, but the data from A.Williams point otherwise (point in case, they might be old, but still). I get what you mean by saying available and not rare, but people would assume that every single blade in medieval Europe (regardless of the high or low period) was spring tempered and we know from metallurgical results that such was not the case especially well before the 16th century. As for the edge hardness, again that is not entirely related on how easy is to break or chip a edge. Edge geometry play a much more important role here. A brittle edge defines is mode of failure more than the likelihood of failure. Softer edges are much more likely to roll and deform (on a microscopic level this is what you refer as dulling), than harder eges. A hard edge is much more resilient against wear and tear, but it will crack upon failure. In Japanese traditional bladesmithing, this is mitigated with several techniques like having "ashi" in the hamon. Moreover, many kotō blades tend to have a monosteel structure and different phases of the steel. One of them, known as utsuri, do allow the blade to deform much more as it is an added layer of bainite. And the hamon in itself has advantages over the crack propagation. I can probably go on even further but I will stop here. Just want to re iterate that the majority of the blades were by large not monosteel spring tempered ones, especially for the medievla periods, but that elastic deformation does not happen only with such structure.

Thanks Matt! Been waiting for u to bless us with original antique flex...thanks again for all the education and hard work

Well done. Wasn't aware that wootz blades were sometimes edge hardened. It's kind of an outlier as well due to its metallurgy, but that's another video. Was glad you mentioned native made Indian swords; I think many people are not aware that the Indo-Persion peoples have a LONG history of steelmaking.

Any idea why this video has more than 50% dislikes? I have been watching this channel for years and never seen such a ratio on your videos. This video is just as good as all your other content

Thank you so much for making this video. It helped me answer some questions I had about some swords in my collection*. Like many people interested in arms and armor, I seem to have answered the siren call of the tulwar. I would love to see a video on how to date a tulwar. Many of them I see are described as "18th century," but, it seems to me this is often just a guess. Truthfully, I've just going with my own sort of guess, so, a video or a good source of information would be appreciated. *Like the commenter below, I didn't know that some wootz blades were edge hardened and this led me to distrust a very nice tulwar.

One thing that fascinates me is the difference in preservation ideas in Japanese vs other swords. It seems so rare to see a Japanese sword that isn’t fully polished whereas most other swords have a patina that is considered wrong to polish off.

Greetings from Croatia !!! Matt Easton I found your channel through Shad (from Shadiversity). I have been following you, supporting & sharing your content since 2015. I'm a small blacksmith from Croatia, many of your videos have helped me improve my blacksmithing skills, I'm very grateful to you for that. I wanted to work with you in the near future, but after your attitude towards Shad, I don't know if you would want that. Because I'm a conservative Christian like Shad is. My question is am I welcomed or not on your channel or should I leave if it's a problem for you, because of my deep convictions. I would appreciate your reply.

The Burmese dharb, is possibly also edge quenched i know that is the way they do/did it in Thailand. They quench only the edge and with the remaining heat it tempers. Anyone knows what book is showing at around 19 minutes, it looks interesting.

Its interesting: you talk about differential hardening in this video, but not about differential tempering. When I was taught about knife making (all theory, I must admit that I don't have a lot of practice at this), I was told to first anneal, or soften, the entire piece, once shaping was finished, just to remove any internal stress or potential breaking points. Next was to harden the entire item: tang, blade, edge, and back; the whole thing together. The third and final step should be (again, I was told) to selectively soften parts of it, especially the tang and the spine of the blade. The edge-hardening methods that you describe seem to start with the same first step: to soften the whole thing after shaping. But then so to a second step of selectively hardening the edge. I can see how this would be faster than a three-step process (being only two steps). But I wonder if there are any other advantages or disadvantages to the two different general modes of finishing a blade. (For those who are wondering: the general rule, with types of steel that can be hardened or not, is that- slow cooling = soft; fast cooling = hard. So, if you want to soften an entire piece, you heat it to a glowing temperature, and then put it in a partially insulated box overnight to cool very slowly. To harden the entire piece, you heat it up, and then plunge it into water to cool very quickly. To selectively soften, you selectively heat part of the piece, and then put it in the same insulated box. The part that was either not heated at all, or heated least, will not change hardness, the part that does get heated will change, to either get harder if quickly cooled, or softer if slowly cooled. So, for knife-making, with selective heating as the third step, you then put it in the same insulated box to cool slowly, and those parts will get soft.) My other thought is whether the reason that certain German weapons were a "messer" rather than a sword is because of using the type of heat-treating used for knives, rather than any of the methods that you described for swords?

At 17:51, you say how people wouldn’t spring their swords if they were going to stay bent, there are plenty of cases indicating otherwise. For example, unbending blades, which was likely common due to the consistency of steel and heat treatment. It’s common today with fencing and HEMA swords for sure.

Great vid, not at all what I expected to watch based on the intro. You are absolutely correct in what you've said. Not only were inclusions and steel quality partly responsible for earlier swords not being spring tempered, the economics of sword building was too.....carbon steel cost a lot more than iron, so it was best used purely on edges (like the bits of many axes, iron all over apart from the cutting edge). You get a perfectly usable sword using 90% iron with 10% carbon steel cutting edges.....so for the same amount of carbon steel in one purely carbon steel sword, you'd get 10 swords by using it creatively - and labour from slaves was cheap. Well done Matt, keep up the good work!

Magic Spoon tastes excellent, but man does it ever get stuck in my teeth. Just in a really impressive way. No other food has ever done that to me.

Do you think survivor bias comes into play with the 14th and 15th century swords at all? Just curious!

It should really be mentioned what sword Adam Savage is handling in a clip, since its literally the most powerfully cutting sword design there is, the type XVIIIc from the Alexandra library. The XVIIIc absolutely dominates the cutting competition world.

Okay, I’ve shifted my opinion from ‘higher quality swords were likely to be spring steel, lower quality ones may have been less likely to be, and often did not survive’ to pretty much the viewpoint Matt is expressing here, Adam’s little trip started my thought process, but really this video’s wide range of sources helped convince me - although really it was the commentary on he commonplace existence of crossbows which hit home the ‘no, they probably all were’ point. But also, I honestly was not up to date on the existing body of knowledge regarding European weapon smithing techniques, particularly the shift from pattern welding to the more widespread availability of higher quality steel that seems to take place towards the end of the medieval period. And also, my viewpoint did include Matt’s ‘there are degrees of spring’ point, but honestly I don’t have the exposure to accurately judge that, and I made some foolish assumptions. An excellent video! Thank you very much for the coherent thoughts!

Hello, do you know that the best Spanish rapiers, were supposed to bend in a way that let them touch the guard with the point of the blade? Cheers

Hi Matt, could make some video about the traditional "ginunting sword" from the philippines? I think it is very interesting one, it's kinda gives me vibes like a Katana but reversed.

Great video! I love this kind of content on your channel!

Never thought a cereal company would sponsor the study of martial arts

I remember reading about the Spanish conquest of the Americas and when discussing the weapons used by the Conquistadors, the book mentioned that Toledo swordsmiths (regarded as some of the best in Europe) took special pride in the flexibility of their swords, and that one of the signs of a true Toledo blade was supposed to be that it could be bent double and spring back to its normal shape. I think the book was John Hemming's The Conquest of the Incas, but unfortunately I don't know what the primary source was for the claim. If it's accurate, it certainly suggests that at least in the early 16th century blade flexibility was a highly-valued quality that people would pay extra for in the right circumstances.

Aaahh! A Muromachi era tachi-blade with ōkissaki, mounted in han-dachi koshirae… Yum-yum! 😋😍

I have tempered hammer faces with the pouring water method. It is effective but not as effective as normal tempering methods, at least in my experience.

I can’t believe that in all the years you haven’t posted about medieval hardening in such depth. Especially with the availability for punning. Very good video.

Your Katana is so beautiful. Could you share some information like the origin, dimension, weight or close up picture? I felt in love with it.

Great video. focusing on content like this is the way to go. Cheers!

I have a question for you how much sword basd martial artist are there

Is that an Albion Ringeck? That's my dream sword!

There is however a ton more evidence that the medieval bloomery steel blades would break if subjected to the same stresses as modern spring steel is routinely placed under. This is due to the relatively high amount of slag inclusions, and lack of homogeneity that is indicative of the material. Within a bloomery steel blade can be high carbon, low carbon, iron, cast iron, wrought iron (coming from a metallurgical study made of Medieval European swords). The majority of the truly spring steel blades came from the east in India and surrounding areas where crucible steel was made (that's where the steel for the famous Ulfbert swords came from). I believe the That Works crew (Iliya) was referring to European (not Indian, Japanese, Chinese, African, Turkish,.......) Medieval (not Renaissance, or Industrial Revolution) Monosteel (not pattern welded, or multi part construction). So if there is a sword of the medieval period that is spring steel, my first question will be "Where did the material come from", because crucible steel was not made in Europe until the industrial revolution.

Random question: What would you consider to be some of the hallmarks of a master sword maker? Are there any makers today you would consider to be masters?

Excellent video, I actually didn't realize (though I probably should've figured) that spring-tempered swords were found outside of late-medieval Europe. I always felt this was an incomplete topic in history RU-vid, and I'm happy to have some gaps filled in.

nice review! How much is sigi king's elasticity compared to the actual sword? Is it more elastic?

In Laksdøla Saga, at Kjartan's last fight, we learn that his sword is soft, so that he often has to straighten it under his foot.

Whenever a topic on a springy blade is brought up, I often ask myself how far does it need to go before we consider it a springy blade? If you Flex a blade, and it goes back to true is this sufficient? A lot of blades can flex to some degree, but few can turn into a horseshoe shape and come back true. I think most agree that such a blade would be considered springy, but how little flex-to-true-in-degree-of-bend do we accept for the definition? When traditionally sharpening and polishing a Katana for instance, you will flex the blade a lot, but it won't "set" that bend. Even then the degree of flex isn't very high nor does it need to be during this process.

were old steel crossbow bows modified in to sword or machete blades? since they are flexible

Rapier survival is a testament to not only the craftsmanship but the steels used.

I love your channel. Thank you for the wealth of knowledge

This was really interesting thanks for sharing this.

I saw a video of a Laotian?Cambodian? smith who used a rag soaked with water and he ran it along the edge. Waited a few seconds, then did it again a it further up the blade. Waited a few seconds and then quenched the whole blade.

All of your videos are such awesome resources, keeping up the amazing quality!

Hi, always love this kind of video with technical details. You tell us hardness in Rockwell, but there's 3 scales. A, B or C at least. I think it's HRC for the europeen swords, but is it really the same scale for the japanese one?

100％ agree: we are certainly spoiled by the quality and consistency today, even for the equivalent of just one day's work we can get a very good sword, but that doesn't mean they didn't have good swords historically!

Now that you have this new Japanese sword (and I see that it is in polish, or close to it), are you going to do the "The Bodyguard" test and drop a light silk ladies scarf on it and see it if cuts it in half lol. I'd love to see that done. Also, great information, all clearly presented and makes sense. Well done good Sir.

Really interesting video, although the conservator in me did cringe when you showed the clip from Adam Savage of the curator bending/flexing the sword....

I have a rapier from the 16. century and the blade was forged in Solingen and send to Spain. The blade is strong but flexible.

The Celts were all the time restraightening their swords during battle according to Roman sources, quite like the Japanese perhaps. It is amazing how you can achieve such high level of excellency on ancient weapons and on advertisement in the same time!

The nuance and *deep penetration* of topics on your videos has always been why i love this channel. As a writer, a dungeon master, and a nerd i love these details that dont make it into the mainstream. Sending all the support i have to give to you and the family Matt, you deserve it all and more.

Kinda curious that the Kasara had the same edge hardness. I would think is a place where people fight essentially half naked and with shields alot, durability wouldn't be that big of a deal and they would want non spring harder edged swords.

Is that true that certain middle-eastern sabers were so flexible one could bend them in a circle such way that their tip touched their pommel and then they came back to true?

25 - 45 rockwell is by definition not spring steel hardened. You can not sell currently a HEMA swird line which is softer than 50+ Rockwell.

One part of this springy tempering history i have always found particularly amusing is that tons of people (historically and modernly today) think all crucible steel / wootz / damascus steel swords are springy. The phrase "could be wrapped around his waist like a belt and return to true" comes to mind. But in my experience, the *vast* majority of pattern forming crucible steel swords are not tempered to be springy, with the exception of the fine grained "crystalline" wootz of late india, and some "sham" kilic. Exceptions exist, but still. Most crucible steel ive seen is tempered to take a set

Thank you for the video ⚔️

Antique blades may fail when flexed due to decades or centuries of corrosion in a forging fault. Otherwise flexed not past its elasticity it can flex many times before it takes a set 😮

Well this just makes me wonder how you can tell how hard the edge is on a sword, or how springing it is. Is it just a matter of experience from handling loads of swords?

Also, and I mean seriously correct me if I'm wrong here, but how could medieval people not have had widespread access to springy swords if we start to see the introduction of fencing, bigger and thinner swords, sideswords, etc etc etc? I thought the whole point about those things existing, like zweihanders, or knights in full plate armor, is that medieval people had better access to quality materials and workmanship needed for those things to even exist at all, let alone be practical in actual conflict.

You produce more quality content than I can watch. Not complaining tho, that say a lot about how passionnate you are.

I'll ask this question again in case someone who knows missed my question last time: quick question: Does anyone (including Matt) know anything about Wilkinson Sword, Wilkinson swords? Context: I have a sabre that has "wilkinson sword" on the guard (like no regimental markings or royal crest or whatever) and obviously it's bloody difficult to google it. Is it possibly a promotional piece or something? The guard is similar to the 1845 pattern but it is more "filled out" and the blade has no fuller or anything, it just has some areas of decoration. Any guidance would be very appreciated

I hope I can spring back to straight after 400 years.

A katana is like my old Russian epee blades. If it bends just pull it through under your foot and its good as new. According to my Russian coach the blades were made from the same steel as Soviet spacecraft. Mind you, per coach, "Everything made from same steel".

have to point out that pattern welding started long before the Roman period, the Celts and Germanic peoples were doing it by then and had been for a fair while

All together now: How hard is it? 😆

How did the federschwert (feather sword) get it's name?

I wouldn't have thought flexibility is better for thrusting than hardness

I do look forward to that katana getting its own video!

Excellent video, Matt!

Are the Japanise swords not even with carbonized and hardened cutting edge? You cover most of the blade with clay. Then put it all into a box full of charcoal. Heat it for a while. And then quench it. That would give the wavy line - difference in carbon content.

It is not uncommon to find, upon metallographic analysis, that some Migration and Viking era swords had soft iron edges and hardened cores. No one knows if this was intentional or due to drunken forge welding.

😳😳😳😳😯😯😯😮😮😮 That katana!!! 😯😯😯 I am the last person to say he's a katana guy, but holy sh*t that's a beautiful blade!

But it's fair to compare hema swords to historical ones? were not hema swords supposed to be more springy for safety reasons? The same I was wondering about rapiers, I think the stiffer in those blades the better for the penetration (not to say they don't have to be flexible)

Yeah Matt, the whole argument about practicing with swords just like the original period weapons makes no sense, even if these originals were stiff. Aren't springy practice swords safer to use because of this give? And would you put a sharp tip on practice swords just for the sake of historical accuracy? I don't think many people would fence if the weapons were sharp.

Its intetesting... Somtimes i talk to some people that i dont want this very flexible wobbely dao ssaber thing that moves like paper. They didnt know what i mean but there answer was for sword like you are showed.. They alllways flexible *some wobbely metal noises*😂

I think the younger guys had stiffer swords and the older guys tended to have more flexible swords. Its a rule of thumb. 😀

Japanese edge of 60 R is comparable to modern tool steels. Even stoning the edge would be time consuming, a file won’t touch it

How about the hardening/toughness of axes/hammers/maces? When were steel bits inserted into iron blades? Does that really even affect the issue of hardness/toughness? My favorite D&D dwarf is often described as wielding a "many-notched axe", and that along with the fact that he lived most of his life above an iron mine leads me to believe that his axe is likely made of iron and not steel. It probably doesn't even have a steel insert.

the “springiness” of a sword is interesting to me.

Yay, Lucy is back!

I've been longing for the day that you'd respond to this, Matt!😃 There is documentation suggesting that many of the famous Medieval and Renaissance sword makers of Toledo, Spain required a sword to return to straight after being bent in a complete horseshoe 🧲 before leaving the shop. Now, when it comes to modern swords, I HAVE SEEN an Albion flexed into a horseshoe before returning to straightness, and it freaks me out because I always think it's going to snap! As for the guy from that channel you're replying to (Ilya?): he's on a literal crusade to stop the recent movement towards taking a more honest look at katanas. He wants to GO BACK to the days when people thought that katanas could slice through unobtainium with ease! That's all.😁

I live near Shotley Bridge in north Durham, which had a thriving sword-making industry back in the day. There was a story, whose details I forget, but it involved a bet made by a (legendary) sword-maker, who turned up at the pub and produced his sword from his hat, with an appropriate flourish. Presumably it came out straight, otherwise everyone would have laughed him out of the room.

It's just a minor point in this video but something that shows up time and time again when I look up historical stuff is just how common international trade was. I would have never thought it was common for an "uncivilized, outdated" weapon like indian swords to have European manufactured blades.

One thing. When metal is heated in a forge the carbon can migrate through the metal, sorry cant remember the rate off the top of my head. So that means with pattern welded steel the carbon will migrate around and can become fairly uniform through out thr blank. So the inculded low carbon steel could end up as moderate or higher steel and end up being hardedable. But the nickle and other impurities don't migrate so that is were the banding can come from if it is etched.

Another common way to get a differently hardened blade is to forge or grind it so the cutting edge is thin before you heat it. Having a thin edge can allow you to get only the edge to temperature when it is quenched. This will give it a soft back or center to a blade with hardened edges.

“Grain-free cereal?” Otherwise known as “cereal-free grain?”

ther are other steel inhalting weapons, like spear head, and other shafted weapons. Ther would less springy probaly; brcause lengt, similar amount of metal shorter head piece. I am wrong?

I’d have to look up the details, but I remember reading in I M Stead’s book on Celtic art from the British Museum about an early archaeologist who delighted in flexing an iron sword so that the tip touched the pommel, as a demonstration to curious visitors.

Context.

this is why when they compare katanas with longswords in other youtube videos, i'm not particularly convinced, i know for sure that the katana is forged using historical steel, and techneqes, but is the longsword? sure, it looks like an medevel sword, but i bet that they used some modern steel, modern forging techniques, and non historical hardness, an utterly unfair comparison, it's like they think, "europe got crucible steel" and think the steel became an super steel, with super hardness.

I made have made some comments on the current drama but I have looked at some of the content on shads second channel while I dont have a problem with most of what I have seen I could see where someone left of me would have such a problem and it is your perogative to deal with it as you see fit so I apologize for my earlier judgment. Also I appreciate you engaging some of these posts and explaining in detail why you made the decision and for family and friends I can respect that Im 25 and you are a role model to me and I am glad to have learned something from you on this issue and more importantly on the products of your labor through this channel thank you for all you do and keep the context coming.

I've had some Magic Spoon, it was pretty good. They stepped up the salt to make it taste, and I was surprised. A slightly salty breakfast cereal is really nice. This is coming from a sugar freak.

uuuh that katana is absolutely gorgeous! is it possible that people think about viking era swords when they say they are not springy? still middle ages but earlier?

I enjoy these more focused points. I would enjoy a video where you go even more detail.

I remember that episode of Adam Savage and the curator bending that medieval sword and cringing. Not something I would choose to do to a 200 to 300 year museum piece but hey they break it they bought it. 😂

I’ve had radial bent British Victorian blades 😮much harder to rectify than a 90* bend.

Uou can make a more flexible blade with hard edge (like a san mai blade). You forge it like a sandwich, with the harder hi-carbon steel in the middle, sandwiched between softer steel on the outside. So when you sharpen it, that core of hard steel makes the hard edge. I think Matt accidentally described it with the harder steel on the outside.

This was pretty hard to miss..