Do You Even Need it? Foil vs Coatings for Heat Treating Steel

[@zapcos80]

A great learning experience. This is what public education should be like. Thanks.

[@TyrellKnifeworks]

Great video, Larrin! Backs up what I've already done with the Condursal, so I'm happy you did this.

[@samdahlandsonsforge]

Hey, thank you for making Condursal Popular to our knowledge Denis, btw. Only issue now is its all sold out on Maritime!

[@TyrellKnifeworks]

@@samdahlandsonsforge I’m sure Lawrence is on top of it and it’ll restock soon.

[@samdahlandsonsforge]

@@TyrellKnifeworks great news!

[@ohiovalleyforge5383]

I love your videos Dr Thomas I use your information for every steel that I use

[@NordicEdge]

Very interesting. Loving the trial and test videos you do. Knife makers will learn from your work for decades to come.

[@CatsSwordsAndCNC]

Great video. At work my experience with 309 vs 321 foil is that the 309 we had a little harder time getting it air tight, but prevented from pinholes forming on the folds. Especially when we are doing larger blades at 1950f+.

[@revilolavinruf]

Yay! my favorite Monday morning education!

[@fencingrocks3]

Great video! For what it's worth, the one time I used Condursal at another knifemakers shop, we used it on AEB-L by dipping the blade into the can and then using a brush to wipe off the excess and then let it drip dry. It seemed to work quite well. I can see the appeal of using these coatings due to cost, because a $50 can of Condursal is much cheaper than foil overall, which just seems to be getting more and more expensive. For my small volume though, I plan on continuing to use foil just because it's consistent and less of a mess to deal with.

[@johncannon3593]

I agree that I don't see much reason to use a coating for low-alloy steels, except that I have one use case where I might try them: I get a TON of good steel, high-carbon farriers' rasps. Despite being an unknown steel, I know they are a decent steel and take a high hardness and are not case-hardened (I test every lot by heating past critical, water quenching, putting in a vise and whacking with a hammer - they all snap cleanly). The Farrier I get them from uses the same two series of the same brand all the time. I use them because I am among the horsey community and they like stuff, including knives, made from rasps, horseshoes (not used for knife blades, but I have used them for a few knife handles). So I made a series of camp knives, and found that whatever they are made of, they seem to decarb fairly deeply (as tested by hardness files). I know this is all very un-scientific, but I feel like if they decarb fairly deeply, then a coating might help post-HT. I plan to try the Condursol and see if I get less surface decarb.

[@kylesvenson2416]

Great video as always! I've been trying the ATP with hit and miss results. Using it with thin 1/16" nitro-V or AEB-L I was getting great hardness with plate quench but any lumps in the coating were causing warps in the steel. I've gone back to foil for thin and small blades but still use ATP for 1/8 or thicker stock.

[@highplains7777]

Thanks. This confirms my experience with 52100 not hardening with NoScale 2000.

[@brysonalden5414]

Always learn from your books and videos, of course! Thanks for sharing your knowledge.

[@S.Vallieres]

Thank you very much Larrin for this great experiment, article and video!

[@samdahlandsonsforge]

Oh thank you for do this video Doc!

[@randallmazzu2064]

Been using foil and aeb-l for 4 years. Great results.

[@normandbujold6677]

Very interesting as always. Thanks

[@F0XD1E]

In aerospace we use the Turco on titanium to prevent hydrogen contamination and alpha case during hot forming or stress relief.

[@entertheFinn]

Thank you for this! Learned a lot and always very appreciative.

[@donhalter8377]

Great video! I would have loved to have seen 80CrV2 included in this. I don't use any coatings and I get very thick decarb with this steel.

[@pierremorel210]

Nice vidéo! For condursal the must important is the perfect clean of the blade and the regularity of the repartition of the paint. I clean my blades with soap and water and after dry, I put it into 98 % alcohol, with nitrile gloves and immediately after dry, I merging the blades into the condursal. I have a good result. But for stay sure I integrally sand the blades after all the heating treatment.

[@nickjohnson5291]

Excellent video as always. If you do the spray can coating, please pick up a can of "high-temp" spraypaint from a big box store, I've always wondered if it would have any effect.

[@CaseDraughn]

Thanks for this video. Just a couple weeks ago I was wondering whether you were still working on this subject. I had just finished my container of NoScale 2000 and was trying to decide what to use next. I'm mostly forging blades in 52100 and 26C3 close to final dimensions, and the NoScale seemed to work quite well. I usually forge, and do one or two normalizations in the forge as I straighten, then grind the profiles. I then pickle them in acid to eat away the scale and wire brush them clean. The NoScale works just fine like that when painted on. If there's scale under the clay then it will pop off either when the blade heats up or cools down leaving gaps. For normalizing and annealing in the furnace, I usually give it 2-3 coats, and for hardening just a single thin one. I'm not sure whether the thick coats really make much difference in preventing decarb but it only takes another minute to do. When I ran out, I bought a sack of EPK Clay and made a bucket of paint with it (in ceramics this is called slip). I don't know what clay NoScale is but EPK seems to work fine though not quite as good as it may have a little trouble drying if put on too thick. I tried dunking in the slurry for a thick coating but some areas want to crack as it dries, so lately I've just been painting on a coat and drying with a torch. It seems to work just as well in preventing scale, though I can't be certain how it does against decarb. The thing which always concerned me with clay coatings, as I have studied ceramics in archaeology, is that the clay is not really impenetrable to oxygen. The clay itself does oxidize as it is held at heat. It diffuses from the outside in. This is why this clay turns a bright white after firing (it has extremely little iron content, so it becomes bright white rather than red). Clays with higher iron contents would turn orange-red in oxidation and black in reduction. I am curious to know whether an addition of finely ground charcoal to the clay coating would help to prevent decarb by preventing oxidation of the clay. Some time back I made my own insulating fire bricks all from scratch with my own wild clay using grog and crushed charcoal as tempers. The cross section of the brick has a stark contrasting oxidation line about 1/2" in. The interior is black/gray while the oxidized skin around it is orange. The charcoal in the dark areas is still present after firing for 5-6 hours - I'm guessing due to insufficient oxygen to burn. Anyway, I might give it a try as I have plenty of clay to play with, but I don't really have issue at the moment with decarb so long as I don't forge too thin or for too many heats. I like to leave a little forge texture somewhere on the blade to show that it has been forged, and the little bit of clay helps prevent that area from scaling too bad since I won't grind it clean.

[@krissteel4074]

Pretty good coverage... ok not my best pun I find the coatings (ATP) very handy for large stainless and high alloy knives as foil is extremely expensive there. You do need to be careful when loading them into the furnace though I've found as you can knock bits off and that will result in localised decarb. A bit of scale though is something most of us can live with as its only a wire wheel or dipping it overnight in cleaning vinegar gets rid of most of it. Coating on water quenched blades I've had some success on 26C3 and 125SC in the sense that I found it immediately flakes off in the quench and seems to give it a much cleaner quench that avoids air pockets and just an overall consistency to the hardening. Its also really handy when you're doing very slim form factor knives which might only be 2mm across the spine so you don't have to grind very deep to find hard metal

[@bernardcaille]

Thanks Larrin, Condursal has worked well for me. I just paint it on and hang it to dry, A thin layer is plenty. I must UP my pre heat treat cleaning though and probably grind to at least 120.

[@Tool-Iron]

Awesome video! I'm very curious about the clip at 14:48 where someone is applying Noscale 2000 to the edge of the blade rather than the spine, which is what I most often see when creating a hamon. I'm wondering if the thinking is that he's going to decarburize the back of the blade and thereby create a differential hardness when he goes to quench it, instead of putting the coating on the back of the blade and slowing the quenching process down enough so that that part of the blade doesn't harden.

[@devindodge8648]

Bro, as always, thank you for your research and expertise. You're such a great teacher, I heard CPM is having issues... will we still be able to get Magnacut?

[@dmw_cutlery]

I always use talc for my heat treatments and it works great every time....especially at very high temperatures where the foil welds to the material.

[@brianbaldwin3700]

Awesome! Thanks

[@Sigurd66601]

I like to heat the blade so that the coating dries very quickly. I also thin my ATP down so that I can get a really thin coat. when I first tried it I got streaks on the blade from my brush strokes.

[@auroraborealisknives4019]

My experience with these coatings is that if there is even a slight amount of oil on the blade (even from touching with your fingers) the coating doesn’t stick well. I much prefer using air hardening steels

[@natsfr]

Hello, Do you think in case we quench full thickness blade we could austenize uncoated (and no foil) stainless steel, on your micrograph it seems the decarb is only 0.2mm. Thanks a lot for all the information.

[@h2tym]

I tried to use atp for magnacut and it didnt affect the hardness too bad. But it is a pain to apply and remove. I personally still have issues with foil wrapping and cant seem to get a good seal. So I may not do much stainless anymore.

[@Wolf_K]

@knifesteelnerds Larrin, what do you know about the Decarburization differences during heating to quench - in water, specifically - using propane gas vs charcoal? No foil is used, just a thin non-commercial clay coating is used. I read that it’s significantly less using a charcoal forge due to the charcoal itself using up most of the oxygen. How much the clay contributes I don’t know. Not necessarily going for a Hamon/differential hardening due to the uniformity of the clay coating. Superficially, at least, this makes sense to me but I have no idea if it’s the actual reality of it as some scale is still present in clay coated charcoal forge blades. I imagine hold times for many steels, as opposed to simply reaching critical temperature and quenching, being much harder to accurately achieve even with a thermocouple installed in a charcoal forge due to the nature of the fuel and thus requiring a lot of experimentation and experience to get it right. (Like traditional Japanese makers, for example) Regards Wolf

[@martindietrich2011]

Thermodur is wirking verry good in my shop. The steel is only litghtly black on the surface from the burned oil. Virtually no decarb or scale.

[@JFirn86Q]

Very interesting. The marketing on these coatings and application techniques I would have thought would work best (like dipping) would have led me down a wrong path.

[@Zonkotron]

Wouldnt it be smarter to have a little carbon in the coat. I remember some old TV show on the filemaking profession, they were brushing on some sort of.....coating. Edit: I found the movie: Salt, Charcoal Dust, Hornmeal and a little flour. The application procedure seems to be coatit with a wet slurry and then dust it with the dry micture to get a thicker, consistent coating. If that is good enough to prevent decarb on file teeth (which are made before hardening) and maybe even caseharden them.....it should do knives just fine ^^

[@Zonkotron]

Its in my native German, but it is a wonderful video: kzbin.info/www/bejne/gYGznGaqbqp0oc0 Including the coal fired hardening furnace ^^

[@Noone-rt6pw]

Would Magnesium hydroxide be useful?

[@BonaganiMbatha_SA]

Grinding a bevel before HT may affect the hardness of the cutting edge?

[@DanielCauble]

Well that's disappointing. I've been using Noscale2000 for a few years, but also use ATP. Of course, only simple carbon steels. Even for water quenching I've used both of these in this mixtures to leave just a paper thin layer. For water quenching I use it with the thought that the thin clay will not maintain a vapor jacket like bare steel would. However, only using ATP and Noscale for both vapor jacket and supposed anti-decarb abilities. I will say that if Noscale was not properly mixed up first and maybe thinned a tad, it would leave streaks when brushed on, but they were not at all noticeable until the blade got hot. For instance I could coat the blade and even dry it over the fire before sticking in the furnace fully. When brought out to say thermal cycle or bring up to austemp, I could then see the streaks. I guess the thinner areas oxidized. I can't say that the blade coating from Noscale has always worked for antidecarb if my name was on that list because I mostly make through the years wide bevel sanmai style knives at full thickness at HT. Which means it's only covering mild steel and the finish it leaves behind was important, which I will also note I stopped using it for because the noscale would almost sinter onto the forged surface and was near impossible to remove without ruining the forged surface that was meant to stay. ATP always washes off. Now I've used both on wootz and still had decarb on blades but was unsure if it was because of the product or me. Thank you for taking the time to do this. It's likely saved me more decarb in the future.

[@ArtemusPrimeK]

Good day. Have a question got you book but didn't found specific information about quinch plates do they have to be only Aluminum or can be other material ? thank you

[@BirdLegacyBlades]

Have you ever tried Industrial Graphite Dry lubricant?

[@revilolavinruf]

I hear a lot of people use barbeque paint. i've also tried using it, but am curious to know if it's viable.

[@01Sigsauer]

Do you have some data on hardness of AEB-L in foil vs coatings? I've heard there might be some differences.

[@KnifeSteelNerds]

After decarb is removed, hardness is the same

[@01Sigsauer]

@@KnifeSteelNerds Thank you for the answer!

[@turbosport3954]

rust-oleum high heat spray paint ceramic coating up to 2000 F

[@HonestDoubter]

I think this test, of all of them, was a bit half hearted. First I would say that Dr. Thomas's contributions to knife steel are immesurable. I own both of his books and have learned a TON. On this one I found that Dr. Thomas doesn't really like coatings to begin with, prefers stainless steels and even super steels among those, and didn't really take the time to learn the product well. His tests on Condursol in particular were not the same as the rest and his finidings were that with simple carbon steels (such as 52100) the product worked well but he doesn't like it personally because he finds it messy. The scientific rigor in this particular test suffered due to biases of steel types how Dr. Thomas feels about the product. If it were a review of the product - that would be fine - but it was supposed to be a scientific comparison by a scientist. I would have liked to see an honest shot at it to see if there is something there - but I think we saw Dr. Thomas's biases showing. Graham Clark of Clark Knives in the UK has heat treated thousands of knives and is also a metalurgist and recommends Condursol in particular for simple carbon steels. With ALL of that said. I am still a massive fan of Dr Thomas, I think he has a point, and was VERY glad to remove a few of these products from my list before ordering Condursol.

[@jamesbarisitz4794]

Would a stream of nitrogen into the foil pack as you fold it work?

[@ExarchGaming]

either that or argon would work. (i think people are more likely to have argon, due to it's use in welding)

[@jamesbarisitz4794]

Agreed. Inert gas seems like a faster, cleaner, and cheaper way to keep oxygen out of the foil envelope than the different goops.

[@hurzelgnurk]

Just a little notice: your Condursal expired 12/31/22.

[@antlerman7644]

Lol, most likely the plastic bottle it came in expired

[@KnifeSteelNerds]

Those are pictures from the internet

[@dylannabity5443]

​@@KnifeSteelNerds so just a question but if I did forge stainless 440c without coating and I don't get too close to final dimensions and I just grind off the decarb with a grinder ill be fine right?

[@loosieclocker]

Would this have helped Suvive?

[@jasonscott7803]

👍✌️⚒️

[@whitegod8755]

I know this is kinda outside your wheelhouse but ive noticed chinese titanium is blowing up these days and there are articles in aerospace that the chinese titanium is fake. I know thats not really what you do and kinda outside your channel but figuring that out would be some impressive content.

[@01Sigsauer]

So Noscale 2000 is actually Bullshit 2000 in a can!?

[@aikonlatigid]

Use clay for free, just add waterglass for cheap sticky hard ceramic

[@dimmacommunication]

FINALLY :) Could you do a video on water quench ? and wich steels are best for it ? I have troubles finding quench oil here and it makes a hell of fumes, in areas with neighbours isn't the best thing. I saw japanese knife makers do water quench

[@KnifeSteelNerds]

Where is it difficult to buy quench oil? Almost anything can be quenched in water it’s just that the risks for cracking and warping are higher.

[@dimmacommunication]

@@KnifeSteelNerds Aside from why I have difficulties finding oil, could you do a test with water/brine?

[@sloanNYC]

Physics is damn complicated.

[@Jake-bt3fc]

This is a video about preventing oxidization.

[@sloanNYC]

​@@Jake-bt3fc I look at chemistry as a field of applied physics, especially in fields like lithography or nano level interactions. But whatever you want to call it. The interaction of particles, atoms, molecules is crazy stuff.

[@britenrhodehouse8692]

​@sloanNYC it's way cool 😎 even if it is complicated

[@sloanNYC]

@@britenrhodehouse8692 Very true. Part of what's fascinating is how properties can change dramatically at a nanoscale or when getting to extremely pure compositions... crazy.

[@mizikacii]

Yeah great work I appreciate it but I think before doing this type of content you should be able to execute the techniques more accurately and then test them… I’m not saying this based on only this video of yours because other contents are lacking of experience and technique. Please be more careful

[@randallmazzu2064]

Been using foil and aeb-l for 4 years. Great results.