Antikythera Fragment #4 - Ancient Tool Technology - The First Hardened Steel

Clickspring

Hey Steven, yes Its an interesting topic. The earliest (surviving) texts discussing the subject explicitly mention salt hence my use of it, but unfortunately they are silent on how it contributes to the process. I've not tried any other chemical compositions but it would make an excellent post grad study topic, if only to determine the true role of salt in the process - Cheers :)

Steven swenson

Hey Chris .. I came across some info on case hardening; I was wondering at the choice of NaCl in the recipe since chlorides seem to be agents of corrosion. I see that NaCo3 and CaCO3 are both used as energizers in recent history... so perhaps this readily available material ( KCO3 and CaCo3) in the ash of the charcoal fire would be something more likely to be used than salt which was VERY valuable... to the point of being used for pay in lieu of hard currency or other goods in the ancient world. Have you tried ash in a case hardening recipe or a washed ash ( CACO3 alone) ?

Clickspring

It will depend a little on your climate Matt - I live in the tropics so I need to sit them in an oven for a few days on low to really dry them out properly. If you're unsure whether its really going to dry properly, then put a small pinhole in the side when you form the clay tube - it won't affect the carburisation process, but it will reduce the liklihood that it goes pop :)

Matt Lukes

This was absolutely fascinating Chris- I've been interested in ancient metallurgy for a while, and everything I'd read previously seemed to make carburizing a difficult process, so it's wonderful to see it's actually very easy! This answers so many questions about ancient tools I'd had, and makes the relatively rarity of proper steely iron and steel from the bloomery process a lot less of an issue. I have a question though: how long did you let the clay vessels dry before you put them in the furnace? I'd really like to try this myself.

Clickspring

Thanks Connor. I've just completed shooting another vid where I use mild steel, again as a non quench hardenable wrought iron substitute, and it serves the purpose quite well, but I'll keep it in mind - Cheers :)

Hello, Chris. I noticed that you pointed out a lack of access to wrought iron in this video. I happen to have quite a bit of puddled wrought iron which is unfortunately red short and therefore almost useless for hand forging (and so of no use to me). I suspect it'll machine quite nicely, though. If you would like some for future projects, I'd be more than happy to supply some.

Clickspring

Hey Erik, its a good question - all of the old texts explicitly specify animal based charcoal (hoof, horn and leather) as being essential for success, but none specify the underlying reason. It would make a good postgrad study. Cheers :)

Erik Larsen

Excellent video, it'd be interesting to know how many times they must have done this process by accident before someone figured out what the key component was. Out of curiosity, is there a reason to use leather to create charcoal rather than wood? I can't think the chemical compositions would be all that different once the volatiles were burned off, and it seems like it'd have been a waste to use something so pricey just for a raw carbon source.

Clickspring

Hey Paul, the best claim I have found is the apparent case hardening of small tools from the early Roman period. It didn't seem too controversial, so I didn't think to save the link. There is also a bit of info out there on the case hardening of Roman blades, so I think its a relatively well accepted. But of course being iron, very little has survived, so like all archaeological claims, its probably still open for debate. Pottery shards would be a clincher for sure! Cheers mate :)

Paul Grodt

Hey Chris, history-minded blacksmith here. I've seen and done similar techniques for carburizing steel, and it's extremely satisfying. Excellent idea for a video. But I was curious if you had any sources that make the claim that the Greeks or other Western civilizations of the time of the Antikythera Fragment were employing these techniques? I know the idea that Wootz was crucible steel, and that China figured out cast-iron in that era and earlier. But I have only ever found claims that we thought that case hardening wasn't figured out until centuries later; though my sources are frequently old, and I'm not to sharp on investigating things like archeological claims. I wonder if we have any pottery shards that look like the ones you made; that'd be pretty exciting.

Clickspring

Cheers Sam :)

Clickspring

It is possibly something that was discovered by accident, a piece of steel left in the fire next to the charcoal too long, quenched and then found to be brittle - something like that perhaps

Sam Robertson

Maybe this goes without saying, but files are harder than s**t except at the tang. This is so screw-on file handles can bite into the corners of the tang. You probably new this, but just in case... Keep up the good work, Chris!

How did they know that they needed to add carbon to the steel in order to make it hard?

Clickspring

I'm so pleased to hear that Aaron :) Great question. Yes I've picked that idea up from watching quite a few knife and sword makers. There is a convenient payoff that it does make it easier to shoot the scene, but I have noticed that the pro's don't quench thin section workpieces like we generally are taught to quench a typical thick cross section part. And I suspect that this is a deliberate part of their quench technique. So I used this file making process to investigate further (I didn't shoot any of it because I figured it was a bit too far out in the tumbleweeds). My observation is that its the best method to control the inevitable distortion of such a thin work piece. The angle of entry into the quench medium is also important. The best way to show what I mean is to prepare a set of very thin mild steel test blanks with straight line reference edges. Throw a couple into the quench flat & fast, and you'll see clear irregularities in the reference edges. Multiple direction bends were common in my test pieces and they would have been unacceptable if intended as real files or blades. Then quench the others in a slow and more controlled way, noting the angle of entry and the face that is facing down into the quench on entry - it gives a much more predictable result. Not distortion free necessarily, but more predictable and controllable. I'll continue to experiment with future file making, and share what I learn with you :)

Clickspring

In this case, I think it is. Brine is faster than oil, which is faster than air. The key is to get down the S curve fast enough so that the transformation to martensite occurs, rather than the equilibrium phases. Air cooling is definitely too slow for a case hardened part. Oil is probably fine, but brine is optimum providing it doesn't lead to cracking

Clickspring

Thank you Jon :)

Aaron

Brilliant stuff, as usual. This remains the ONLY YouTube channel whose new videos cause me to drop literally anything for a watch. Or three. Quick question of the quenching: you consistently show a somewhat slow, tip-to-tang immersion. Is there particular metallurgical benefit to not dunking the whole thing at once and going in that particular direction, or is it just for the camera?

Is the brine quenching necessary for the process? Would the qualities of the case hardened steel change if it was oil quenched or air cooled?

I remember sitting in many complex and mind-numbing university lectures on this stuff and in 8 minutes you (again) ran laps round the professors! Truly impressive how you manage to distil just the relevant essence of science and technique together into such easy to comprehend pieces.

Clickspring

Cheers mate! This is the clay that I used: <a href="http://shop.walkerceramics.com.au/AA21/Feeneys-White-Stoneware-" rel="nofollow noopener" target="_blank">http://shop.walkerceramics.com.au/AA21/Feeneys-White-Stoneware-~10kg-NEW/pd.php</a>

Clickspring

Thank you Matt, will do :)

Clickspring

Thanks very much Rob, more on the way today :)

Clickspring

Cheers Greg :)

Khanh Khong

Excellent video illustrating case hardening of steel. As a hobby blacksmith, I love this kind of stuff and finally have a great source of information to share once this is public. I can't wait to see the video of the teeth cutting of the files. Have you ever made a flint striker using this method? Less machining than your fire piston, but would be closer to being period? Also, what kind of clay did you use? Cheers!

Matt Waite

Once again the previous commenters have beat me to all the best superlatives. Another example of your outstandingly high production values delivering concise, detailed and fascinating content. Don't change what you do and how you do it!

Robert Liesenfeld

Fascinating! I really enjoy the historical aspect of this build, and you are an excellent educator. Looking forward to more!

Greg Nixon

That's an impressive tutorial. I love the detailed sequence of events. An outstandingly good video.

Clickspring

Thank you mate :)

Clickspring

Ha ha! Thank you Tom!

Clickspring

Thanks very much Rob :)

Outstanding!!! Simply outstanding video, research and thinking. Kudos Chris

Tom Colson

How can you do anything but love a project that encompasses tools and techniques from making charcoal to 3D animated models? And how can you do anything but admire someone who will put up with the stench of burning leather for our great benefit? Another great episode!

Robert Sindorf

Clickspring continues to be one of the most interesting channels on the internet.

Clickspring

Awesome Jess, appreciate your support mate :)

Clickspring

Thanks very much Andrew :)

Clickspring

Cheers Ron!

Jess Neal

What a cool/neat video Chris. I was surprised at how brittle you got the sample rods. Very cool to see the penetration of the case hardening. I ordered a fire piston too. Thanks for the discount code :)

Andrew Smith

I really enjoyed this video in that it showed how you make the basic tools from which greater things are built. Give me a $5 option and I'll increase my pledge.

Very interesting indeed great work learning allot from these videos Thank you ver much!

Clickspring

Thanks Jace, fixed :)

Clickspring

Ha ha! Terrific mate :)

Clickspring

Yes certainly Michael - in fact I harden a file cutting chisel in the next video using the same process. Its definitely inferior to a modern high carbon steel in a number of ways, but if its all you've got (ie 200BC, plenty of wrought iron, limited Wootz crucible steel), you can definitely get an acceptable result if the limitations of the process are managed.

Clickspring

Thanks Dean :)

Clickspring

I wondered the same thing Paul - The texts that I have that reference the subject don't mention the quantities/ratios, so I used trial and error to find out what would work. I guess they must have done the same?

Jace Walton

one of your Notes links is only half hyperlinked my friend. The Phase diagram

Jace Walton

Not sure which is cooler the vigeo or those references!

Micheal Malsed

Chris - question on hardening like that - could you do that with a knife blank? Start with soft steel, wrap it in the carbon mixture and then clay, then case harden it and temper it? Do you know how that might compare to working with carbon-steel to begin with?

Dean Thompson

Some impressive sleuthing on display here Chris. I eagerly await your next installment.

Paul Busby

Brilliant. Again. Your videos explain things so easily. The bit i always wonder is what where they doing and how did they find the ratio's to use. How did they test if it worked.

Clickspring

Will do Mike - So pleased to hear the fire piston is going down well :)

Mike Davey

Chris, truly amazing. While I have build metal lathe using a charcoal foundry, never once did it occur to me to make files from scratch. My hats off to you sir! This is the best think ever and I hope to see a bit more about how you cut the files. BTW, the fire piston never fails to impress when I demo it. They always say, what's inside, when I tell them air, it starts a good conversation. Keep the great stuff coming.

Clickspring

Ha ha! Wait a second... let me write some of this down.. :)

Love it, such a great vid as usual! But now that I know the "real reason" you are building this, for ToT, I'm a little worried at the consequences! AvE as president, AWESOME, but Avon79, seems a little bit of a waste of talent. What other unforeseen events may take place??? Will oxtool now be a YouTube prank channel, will Codyslab now be all about UFO theory, will grant Thompson be the king of particular? Please be careful. 😜

Clickspring

Awesome to hear that Al :)

Al McKague

I too look forward to every video. As a metallurgist who has been banging around melt shops for 40+ years, I find the historical perspective fascinating. Thanks

Clickspring

Thank you mate :)

Clickspring

Thank you Rob!

I agree with matt. There are plenty of great machining channels I've subscribed to but there's only one I'll hand my cash over too. I really do look forward to every vid you produce mate

Rob C

Chris, it really is fantastic to see how much you are enjoying learning about these ancient techniques. Couple that with your desire to share and you have a winning formula. Great job all round!

Clickspring

Cheers Matt, thank you :)

Clickspring

Thank you mate :)

Matt Syme

There is no other channel I look forward to as much as this one. Love every aspect of your videos mate. Thanks!

Ruben vd Merwe

Hi Chris, like the other comments, very awesome the stuff you show us. Thanks for your time and the homework you do to educate us in a very enjoyable format. Much appreciated Chris!

Clickspring

Terrific to have your support mate, thank you :)

Chris Talbot

Wow mate... when many creators say a they have more content "on its way soon" (per your reply to my comment on the "Supertape!" vid), they mean it's a couple of weeks away, not a couple of days... top work! :) I'm loving the archaeological approach you're taking with the tool making and the "Fragments" videos, it's all fascinating stuff.

Clickspring

Cheers Scott, its on the way :)

Scott Clausen

Fascinating stuff and would love to see the making of the files as another video. Looking forward to more.

Clickspring

Cheers Frank, on its way soon, I'm in the shop now shooting some of the last scenes :)

Clickspring

As I mentioned in the post above Jason, the other video is not yet complete - Cheers :)

Frank Donahue

Wow another great video from one of my favorite creators so worth the long wait too, I don't know why I had never thought of leather as a source of "working" charcoal for case hardening I look forward to seeing just how you made your files too

jason black

That's pretty cool. But wouldn't it make more sense to release the "how to cut a file" video before the "how to case harden" one?

Clickspring

Thank you very much Mike :)

Mike Stone

I am a Patreon to a few people whose work I enjoy, but none are filled with as much passion as yours. I absolutely love your videos, your work and your ethics

Clickspring

Ha ha! Cheers mate :)

Chris Muncy

Fantastic as always Chris. Thanks for not releasing this during working hours here in the states :p

Clickspring

Ha ha! Shhh! Not a word!

Nathan Davey

Does your wife know you were using her custard dish?

Clickspring

Awesome Braden, so pleased you enjoyed it mate :)

Clickspring

Cheers Paul :) Truly having a ball digging into this machine. Its so interesting that the device itself is basically guiding the path of where the videos go at the moment. There are a couple of tools implied in the design that I just can't wait to get started on building.

Legitimately had no idea that's how charcoal was made haha. Very cool. Ans the process of metal hardening is truly fascinating. I loved how you did the sample rods at the different cook times and showed the progression of the carbon into the steel. Fantastic stuff, as per usual.

Clickspring

Cheers Ryan, so pleased you enjoyed it :)

Paul Devey

Thank you for the lesson on metallurgy and ancient metallurgy. You definitly have dived in deep with this project. I sincerely hope that will Patreon you are able to fully enjoy this pursuit. Paul

Ryan Das

You continue to blow my mind Chris. It's great to see the stuff I learned in material science being used out in the wild :) Keep up the great work mate!

Clickspring

Cheers Damien - Yes the next Fragment video is all about making the files. I have most of it in the can, I just need to get a few more shots and narrate it - keep an eye out for it over the next few days :)

Damien Miller

Great video - I really appreciated seeing the cross-sections of your test rods. I'm interested in how you made the files - are you planning a video on how you made them?

Clickspring

Thanks Mark :)

Everfalling

really cool stuff