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I've been experimenting with natural clays for heat treating. Satanite works great, but it doesn't have as fine particles as typical red clay or river clay. However, there are many different types of pottery clay available. Each clay has its own shrinkage characteristics, high and low fire temps, some other variables. My guess is that a high to medium fire clay with very low shrinkage is ideal. Some elements may need to be added to help increase stickiness, insulation, reduce shrinkage etc.

I started with 'earthenware' clay, which is red and very fine. It has low shrinkage and can be fired up to ~2000 degrees. I'm heat treating between 1400 and 1500, so anything that can fire above that should be fine.

Applied to a rough filed blade, 23 inches or so in length. A thin wash first, then the thicker part to insulate the spine, then ashi.

The ashi are really really nice with this clay, especially compared to something coarse like Satanite.

This dried overnight, and in the morning the thicker parts either peeled off on their own or fell right off at the slightest touch.

The only thing left sticking are the thin wash along the edge and the ashi.

I tried a few more times with different mixtures and types of clay. I added ash, powdered water stones, charcoal and some other stuff, but neither of the natural clay will stick very well.

I did have success with a W2 tanto sized blade about 10" long using a much thinner layer. The W2 only needed about 1/8" of clay to do the trick.

 

I think the next thing I will try is digging up the red clay from the ground. I assumed the earthenware clay was the 'right stuff', but if it won't stick to the blade, its not going to work.

 

Anyone else have luck with any of the natural pottery clays? How bout digging it out of your back yard or off the river bank?

 

thanks,

-Brian Madigan

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Brian

 

I have been thinking long and hard about that, and I may have a solution. I used to live in Western KY and that area is a very wet low lands, I worked for a Clay Company, they actually mine the clay we use and if I am not mistaken they sell it by the 50 lbs bags or atleast they did back in the day. Now they have several different types and I will have to check around, but I think that may be the solution, powdered clay that is.

 

 

So let me make some calls and see if I can still get a bag or 2 and if I can I will send you a few lbs to play with and maybe we can come up with something.

 

Ok some of the fellows I used to work with still work there so I will place a call to them tomorrow and see if I can get some clay.

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have you tried APG #36 Refractory Cement:

 

This high temperature refractory mortar/cement is the stuff that the late Bob Engnath promotes on his website for clay coating blades as well as the material that Walley Hayes uses in his Katana making videos. We are now offering it in small quantities as an alternative to Satanite for clay coating.

 

- 3200 degree temperature rating

- Wet, High Strength, High Alumina Mortar

 

1 Pint = $6.00

 

 

APG #36 FAQ

 

from darren ellis ????????????????????

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John

 

I have tried it and satanite is actually better in my opinion, but even that has alot of grit to it, I think that we want to see what we can create before we retry APG #36 or satanite.

 

 

so please bare with us on this.

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I started playing with local hardware store furnace cement called Rutlands on advice from people like Patrick Hastings and Rick Barrett. I figured it would be hard to find, seeing as how it was supposed to work so good. Turned out it was right on the shelf in the Ace hardware store in two sizes.

 

This stuff applies like a dream compared to Satanite. It sticks good and stays on, even in the quench. I usually have to chisel the stuff off the blade after quench. I just use a tool I made to scrape the stuff off and clean up on the grinder.

 

It does need to be thinned, it's pretty stiff right out of the can. Just add water and knead up until right.

 

A couple of bad things (relative). It sticks. I forgot to clean up the plate and spatula I use for claying, and the stuff dried to where I couldn't get it off. Clean tools up right after use and all's fine.

 

Also, if you use it right away, after claying, it will puff up on the blade. I was told not to worry about it as it adds insulative value, but it's a little disconcerting. The puffyness will also start cracking and falling off if in the fire too long. I would usually normalize with clay on with Satanite with no problem, but I normalize a bare blade before claying up with the Rutlands. Just more time.

 

Playing with clay formulas might get results but I see it kind of like playing with unknown steel.

 

 

Dan

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Dan

 

Thanks for the info I will go out and look for some to buy. How course is it? I mean is it like Satanite where you can feel the particles as you apply it. What is your mixture ratio? Um never mind I will play with it and then post my results and Brian could you do the sme maybe if we canget a few more people to try it and post results we can figure out a decent formula for general use.

 

And thanks again Dan

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you can wrap a dozen or so turns of mild steel wire around the blade.....this will greatly help hold reluctant to stick clay in place.......

 

 

ps........ we could grind up a batch of satanite or sift it thru a screen :)

Edited by john marcus

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The Rutlands cement (it's sold as a mortor for laying fireplace bricks, I think) is very smooth which is what suprised me about it. After using Satanite primarily and trying some home made concoctions, I was pleased as punch with the Rutlands. I mix it by eye mostly, just to get the consistancy that I like. Go easy with the water as it's easy to get it over done, too runny. I just add bits of water as I go, in a dedicated mixing bowl. I used to just mash it up with my hands but I think there's a good amount of lye or something (part of a traditional mix, btw) in there so gloves would be good. I borrowed the wife's potato masher last time, which worked pretty good. The stuff is black, so carefull with where it goes. Like said, clean up is easy with water while still wet.

 

I've done the grinding, wire wrap, stand-on-yer head thing and managed to disappoint myself most of the time. I got to the point with Satanite where I could just apply it on a prepped blade and take it right out to the forge and do my thing. I still keep Satanite around to use for claying, just in case this new stuff goes hinky on me, but so far so good.

 

Here's a small one I did while ago, a test one out of W1 steel, quenched in Parks 50, using the Rutland's cement.

 

IMG_1871.JPG

 

 

 

Dan

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Nice knife Dan!

 

Anyone tried mashing up satanite finer with a mortar and pestle? A good tip I find that if you apply the clay, and let it dry overnight you get little to no shrinkage and it doesn't pop off when you heat it. If I try heating the rutland right away it bubbles off, satanite bakes hard.

Edited by Sam Salvati

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I have a coffee grinder I use for grinding charcoal powder or iron oxide, maybe I'll run some satanite through it and see what happens. I would hate to think what the coffee would taste like if I used that grinder to grind beans :lol::lol:

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Thanks for the interest!

John, just for reference, these are the clays I've tried:

http://www.dickblick.com/products/amaco-no-67-indian-red-earthenware-clay/

This one is very fine and extremely nice to work with, but any more than a thin wash will peel off when dried. After drying for a few hours it feels very solid and looks like it will work fine, but dry it out more and it falls right off.

 

and I think the other one is this:

http://www.dickblick.com/products/blick-talc-free-white-clay/

This one has higher sand content, but its still much finer than Satanite. I used a 1/8" layer of this by itself and

 

I was recommended this one by another forum member:

http://www.dickblick.com/products/amaco-no-27-white-sculpture-raku-clay/

 

but it was not in stock. So I have 2 25lb bags of each. So I tried 50/50 mix, and one of each by itself, one of each with powdered stone, charcoal, etc. But none of that stuff really helped it stick.

 

I'm going by Ace today on the way home; maybe they'll have Rutlands. It sounds like getting it off of the blade sucks though. I don't want to get that stuff in the water mill. But I could use some anyway to stick some soft bricks together.

 

As far as grinding Satanite down, I didn't have much luck doing that by hand. I did see a pigment grinder at a yard sale that would probably work. It has a bunch of glass beads/marbles which grind anything softer than glass into a fine powder, depending on how long you run it.

Sifting satanite through fine screens might work too. It has significant dust sized particle content.

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Brian

 

That sounds good as far as the clay goes, me personally I have not really tried any as they seem to weak for what we want to do. As for sifting the particles out of satanite would seem to be counter productive as it is those very particles that make it what it is and if you take from it, it would not do its job.

 

 

I am very interested inthe Rutlands so I will be picking myself up some this weekend.

 

 

Brian keep us up to speed on your results, and I will do the same.

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All I have ever used is natural clays. I discovered very early on ( actually my wife enlightened me ) that I had to include a ceramic binder called GMC gum in my mixture to keep the clay from shrinking excessively and falling off the blade. You should be able to obtain it from any ceramic supply store.

Good luck

 

Louie ( Yasutomo )

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You can use cellulose (paper). :)

You can get it at the home improvement stores as insulation material.

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I agree with Jesus. Cellulose is the way to go. CMC Gum is okay, but I prefer celllulose. The key is to add binders that will both deflocculate the clay--making it more "wet" without adding the great shrinking-agent water, and inhibit shrinkage by adding bulk from non-shrinking agents. Also, red clays (actually ANY sedimentary clay--ball clay, etc.) will have a fairly high shrinkage rate. Usually in the 15%-20% range. To be compatible, you will need to mix a clay body that will have no more than about 7-8% shrinkage or less. This can be done with a binder (cellulose), low-shrinkage clay (fireclay or kaolin), and/or non-shrinkage fillers such as grog (which can be as fine as dust--molochite is ground porcelain and can look like powdered sugar) or silica. For stickiness, you will actually need a fairly plastic clay, which will mean more shrinkage--so you will have to balance that with the other additives. My clay is simple: OM4 Ball Clay (sticky, high shrinkage clay), Bentonite (super sticky, super high-shrinkage clay), 400 mesh grog (pre-fired and ground fire-brick that is ground fine enough to be a fine powder), charcoal ash w/ charcoal leavings (ground in an old coffee grinder until a fine powder), and a pinch of home-made paper pulp. This mix dries w/o cracking, insulates very well, and does not fall off in the quench. Also cleans off very easily w/ water and file post heat-treat, which is very important to me. Hope that helps in your quest for a better clay.

 

Shannon

Edited by J.S. Hill

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Never thought of cellulose. Thanks, this is very informative. It really helps to be informed while experimenting

!

 

Ah, OM4 stands for Old Mine #4.

Edited by toxonix

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Yep--Old Mine #4. If you can't find it, try Foundry Hill Cream. Or Tennessee Ball. You never know which mines have shut down. OM4 is sticky and cheap. The bentonite is the key to stickiness. But more than 3-4% and it will just peel right off because it has such high shrinkage. But don't try Redart w/o major modification/additions--it will peel off as it dries--too much shrinkage in the fine terra cottas.

 

But you have to be sure the steel is not too smooth. Draw-filing gives an excellent "keyed" surface for the clay to hold on to. This precludes ANY clay formulations. Regardless of the clay recipe, if the steel is too smooth, it will let go due to the totally different thermal properties of the ceramic vs. steel.

 

Clay and steel have different shrinkage / expansion/ contraction ratios all across the board. The cellulose pulp helps to level out the properties of the ceramic to better match the steel as it is heated / quenched. That is why clay falls off during quench--it has shrunk too much and sintered too hard compared to the steel. If you are having the clay fall off only when it hits the water, then the solution is to raise the maturation point (remove any fluxes--worst one is borax!), and add stuff that won't shrink (grog, etc.). You wanna clay body that is sticky, refractory, does NOT sinter, and is somewhat flexible. The pulp and charcoal help with the flexibility, refractoriness, and lower shrinkage. Do NOT use any fluxes or spars--these make the clay too glassy which equals shattering and falling off. And I use a higher percentage of the charcoal in the clay for ashi--you can vary insulatory properties to suit your steel and the school of hamon you are mimicing. I find I need the main body clay to be more refractory and the ashi clay more fine and a good deal less refractory. This just depends on how sensitive the steel being used is. I believe in making the tools you need to do the job you want. Not just making the work you can w/ the tools at hand.

 

Can you tell I was formerly a production potter for 12 years?

 

Shannon

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Can you tell I was formerly a production potter for 12 years?

 

 

Hmm, well now that you mention it.. you do have quite a bit of knowing.

 

I do leave the surface as rough as possible after draw filing. I use the edge of the file at an angle. It leaves a surface kind of like a double cut file.

I have been sifting ash and charcoal and adding to the finer clay for Ashi.

I noticed in some of the pictures of Yoshihara that his ashi are almost black compared to the body of the clay.

 

The tools I have for applying clay are mostly shaped pieces of wood similar to those use for clay carving/shaping.

For Ashi I find a thin strip of wood that has a nice narrow V shape. The clay has to be mixed until it is exactly the right consistency so that when I card it a bit and dip the edge of the wood in, it draws up a very fine and straight ridge. I think it is the thixotropic properties of some clays that makes them best for this.

Edited by toxonix

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Absolutely. The thixotropic nature is what allows the clay to go on thin, but stay in place where it is intended. Deflocculating the clay will help make it more thixotropic. Very minute amounts of soda ash and or Epsom Salt can help with this.

 

Sounds like you are on the right track w/ your ashi. Just depends on the steel and its senstivity as to whether it will produce effects or not. It is the itsy-bitsy hataraki of the hamon that makes it a hamon and not a temper line--and is also what makes hamon worth the pursuit. IMHO, of course.

 

Shannon

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The finest grog I can find is "Brick Grog Super Fine - 48 mesh" (continental clay)

...

 

Do you grind and sieve the grog to get it that fine? 48 mesh would be ~0.3 mm granules. I could get that ball mill rolling and make a huge mess.

But I'd need a very fine sieve

I save all of the powder from cutting soft fire bricks. It's not very fine, but could be ground further and screened.

 

[edit] axner has 200 mulcoa grog [/edit]

Edited by toxonix

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Has anyone looked up Rutlands Stovo Stove Mortar here is the link this stuff is expensive

 

Click here

 

Wow

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The 200 mesh grog from Axner will be like flour and make the clay very smooth. The 48 is probably the same size grog as what is already in the Satanite, so you wouldn't be doing better as far as making a smoother clay. If you have a soft-firebrick, you CAN grind it up in a mortar/pestle and then screen it to get out the large chunks and use the powder. Same thing as grog. I believe that is what Randal Graham used to use.

 

Don't care for the Rutlands or APG 36. Rutlands is like getting thick, dried paint off w/ all the scraping, and APG 36 puffs up way too much to hold a pattern or make ashi. Just my humble opinions, of course.

 

Shannon

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Has anyone looked up Rutlands Stovo Stove Mortar here is the link this stuff is expensive

 

Click here

 

Wow

 

 

thats the six pack pre mixed.......... pretty sure you can buy it dry.......

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I bought the Rutlands in a single, small tub off the shelf, not a six pack. They had two sizes, a pint and 32oz I think. Wasn't more than $6 or $7 for the larger, I believe.

 

I don't think it was that particular one, the Stovo. It was the "Stove Refractory" I'm pretty sure. I'll have to go back and pick up some more. The web site had three different kinds of motor, didn't notice that in the local ACE store. Just the one I picked up to experiment with.

 

Yep, the getting the stuff off after quenching was one of the downfalls but it does stay put when you want it to. I havn't tried soaking in water afterward, probably should. It's all a tradeoff, or can be. The scraping is minor if it gets results. I know if the clay you use falls off before the quench, it's a worse solution.

 

The Rutlands also puffs up if dried in the forge too fast (like I do). I'm too impatient to let a blade sit and dry for days, but it does dry over that time and may not puff up so bad if left to do so. Another experiment.

 

Dan

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