How Japanese Masters Turn Sand Into Swords

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Published 2024-03-21
This is a video about how Japanese samurai swords, aka katanas, are made – from the gathering of the iron sand, to the smelting of the steel, to the forging of the blade. Head over to hensonshaving.com/veritasium and enter code 'Veritasium' for 100 free blades with the purchase of a razor. Make sure to add both the razor and the blades to your cart for the code to take effect.

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A massive thank you to John McBride for making this entire project happen. This would not have been possible without John. Please check out his japan walking tours walkjapan.com/
Massive thanks to Craig Mod, Inoue-san, everyone in the Tanabe family, and Takanashi-san. Also a massive thank you to Kevin Cashen – cashenblades.com/

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References:
Tanii, H., Inazumi, T., & Terashima, K. (2014). Mineralogical study of iron sand with different metallurgical characteristic to smelting with use of Japanese classic iron-making furnace “Tatara”. ISIJ international, 54(5), 1044-1050.

Tate, M. (2005). History of Iron and Steel Making Technology in Japan Mainly on the smelting of iron sand by Tatara. Tetsu-to-Hagane, 91(1), 2-10.

Krauss, G. (1999). Martensite in steel: strength and structure. Materials science and engineering: A, 273, 40-57.

Krauss, G., & Marder, A. R. (1971). The morphology of martensite in iron alloys. Metallurgical Transactions, 2, 2343-2357.

Yalçın, Ü. (1999). Early iron metallurgy in Anatolia. Anatolian Studies, 49, 177-187.

Kapp, L., Kapp, H., & Yoshihara, Y. (1987). The craft of the Japanese sword. Kodansha International.

Matsumoto, C., Das, A. K., Ohba, T., Morito, S., Hayashi, T., & Takami, G. (2013). Characteristics of Japanese sword produced from tatara steel. Journal of Alloys and Compounds, 577, S673-S677.

Inoue, T. (2010). Tatara and the Japanese sword: the science and technology. Acta Mechanica, 214(1), 17-30.


Images & Video:

Great video from NHK – ve42.co/NHK



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Special thanks to our Patreon supporters:

Adam Foreman, Anton Ragin, Balkrishna Heroor, Bill Linder, Blake Byers, Burt Humburg, Chris Harper, Dave Kircher, David Johnston, Diffbot, Evgeny Skvortsov, Garrett Mueller, Gnare, I.H., John H. Austin, Jr. ,john kiehl, Josh Hibschman, Juan Benet, KeyWestr, Lee Redden, Marinus Kuivenhoven, Max Paladino, Meekay, meg noah, Michael Krugman, Orlando Bassotto, Paul Peijzel, Richard Sundvall, Sam Lutfi, Stephen Wilcox, Tj Steyn, TTST, Ubiquity Ventures

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Directed by Petr Lebedev
Written by Petr Lebedev and Derek Muller
Edited by Trenton Oliver, Jack Saxon, Peter Nelson
Animated by Fabio Albertelli, Jakub Misiek, David Szakaly
Filmed by Petr Lebedev and Lui Kimishima
Produced by Petr Lebedev, Derek Muller, Han Evans, Giovanna Utichi, Emily Taylor
Additional research by Gregor Čavlović
Thumbnail by Peter Sheppard


Additional video/photos supplied by Getty Images
Music from Epidemic Sound

All Comments (21)
  • @shangerdanger
    finally a video that's just about material science so a dumbass mechanical engineer like me can understand it lmao
  • Props to Peter, this must've been intimidating at times and he did a great job being respectful and appreciative of the opportunity.
  • @AAbattery444
    Do you guys remember when shows like planet earth and the discovery channel pumped out interesting documentaries with this level of production quality? I miss those times. Shows just don't feel like this anymore. Thank you for bringing back that feeling veritasium. You guys can't get enough credit.
  • Hi Veritasium and Derek. I'm a descendant of a Katana blacksmith in Japan. The craft in my family has been continued up to the end of Edo era and no one is a blacksmith anymore, but my family had swords inherited from our ancestors. Thank you very much for your appreciation for the art of sword making in Japan. I enjoyed this video more than any other videos of yours since I found you 9-10 years ago. I've watched every single one of them since then.
  • @user-tp5tf5gs3l
    As a Japanese native, I can’t thank you enough for making a video on this subject. The metallurgy associated is just so fascinating and getting the neat graphics and explanations was awesome. Thanks for spreading the Japanese culture!
  • As an amateur American blacksmith, I truly appreciate you making this video. The history and techniques of Japanese sword making is fascinating and should be understood by anyone that wants to learn blacksmithing. Thanks again! Great video!
  • @neophoys
    18:20 slight error here: The combination of Ferrite and Cementite is Pearlite, not Perlite. Perlite is a volcanic glass, mostly made of silicates and used in gardening for its high porosity that helps to aerate the soil and provide microrefugia for microbes.
  • @Darockam
    What amazes me is that we're now perfectly able to explain in details all of the mechanisms involved along a process that emerged solely from trial and error. Science is amazing.
  • We owe it to these Japanese craftsman. No modern science. Just skill practice and repetition. Absolutely beautiful
  • @kajeralocse
    I love how they preserved the rituals involved such as praying. This takes the hardwork and output beyond physical realm, to a spiritual realm. It gives meaning to what they're doing. The level of faith and respect to the elements is astounding. Thank you for showing this to me Veritasium!
  • @shangerdanger
    meanwhile i can craft a steel dagger in skyrim in 4 seconds. we've come so far
  • @nadabutsi7537
    Small correction. By folding the steel you will actually lose a lot of steel due to slag and pieces flying off, the more layers the more material loss will happen. Alec Steele on youtube who specialises in modern damascus talked about this in one of his videos
  • Japanese craftsmanship can be defined by one word: patience.
  • @bass-dc9175
    There are a few things here that require correction or additional information. 1) "They are strong and sharp enough to slice a bullet in half." You can do the same with a $0.5 mass produced, cold stamped butterknife. As Penn and Teller demonstrated. 2) "The method for making these swords has remained virtually unchanged for hundreds of years" Both the gathering and production of the Ore have been enhanced with modern techniques. From more efficient automated bellows to sifting methods for the collected sand using electromagnets to remove most of the impurities which would be present in purely traditional iron sand. And ofcourse the forging of the sword itself with electric hammers which also result in a way better quality sword, because of the consistency of the strikes. And that is not a bad thing. 3) "They are still considered to be among the best in the world." And this is: Inaccurate. Even in terms of Katana: Modern high-forged, mass-produced spring steel ones, will outperform traditional katana. 4) "One sword has been appraised at 105 million dollars, making it the most expensive sword ever produced" Appraisal price has nothing to do with how expensive a sword should be. That is rather missleading, because if someone were to appraise a sharpened butterknife at 106 million, that would not make it the most expensive sword. Because neither the labor cost nor the materials used justify that price. The reason it is valued that high is because of its representation of historical value, less to do with the sword itself and more the culture around it. 5) "Only steel made in this way (Tatara method) is used in the best japanese swords." Incorrect. As previously mentioned: Modern high-forged, mass-produced spring steel ones, will outperform traditional Tatara katana. They are however still amazing pieces of art, but calling it "the best japanese sword" is missleading. 6) "80% Pure Iron sand is an excelent source material for high quality steel" (Context: Compared to Iron Ore) Only if you, do not refine the Iron Ore further. As soon as you refine both the ore and the sand equally, you get much better Iron than what was produced from traditionally collected Iron Sand. 7) "The edge of these swords is much harder than it is in the west" That is: Accurate. And it offers one of the differentiating advantaged and disadvantages that I would have loved to hear here. Harder Steel is more brittle, but keeps it edge better. Making it exceptional agains cloth and layered soft armors or flesh. It cuts exceptionally well. The tradeoff is: Hard armor can shatter the blade more easily. Which is why as armor technology advanced: The blade became less and less relevant. Piercing weapons dominated. And spring steel is still hard enough to keep an edge exceptionally long, while being way more resistant to damage. _____________________________ To finish this off: This is not meant as a "european swords were better" style comment. The skill required to produce these Katana is amazing, the restrictions they had in terms of material led to techniques which compensated for a lot of it and the swords are indeed pieces of art which deserve admiration. I merely want to pushback against the missguided beliefs of the "Katana-Super-Sword" and the "Near-Perfect-Steel-Making" techniques that is widespread, even in this very comment section. QUOTES: "These swords are literally the physical embodiment of trial and error in a form that cannot be perfected further" "Katanas are just the best overall swords in the world." "It is amazing that they made the best steel to this day using only sand." There is value in keeping tradition, but these beliefs are objectively in error. Remember where you came from and embrace the lessons learned with modern tools. THAT is how you make the best product. Not overglorifying what was merely done out of nessecity.
  • @JustusScottJr
    I've seen only a few really good documentaries about katakana in English. This is the best I've seen at explaining the material science. Very well done. Thank you!
  • Hi Peter, it's a great video. I liked the way you explained each process even though I knew few processes i didn't know why they are for. Thanks for the clarification. I appreciate that you are grateful and you had a huge respect for the opportunity you got. All the best. Looking forward for the next video.
  • "whatever you do, you should do it with deep care, attention to detail and love for the craft. Do that enough times, and you might just make something wonderful" - Veritasium