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Hello everyone. This is my first post on the forum, and had two questions about charcoal forge in genreal. I have completed 80% of my forge build so far and have decided on a clay/ ash mix for insulation. My first question is what minimun thickness of insulation should I apply at the bottom of my firepot? And the second, how deep of a fire pot would you recomend? also any recommendations on width/ size would also be helpful.

Thank you, I love projects and am already having a blast, can't wait to start hammering some metal.

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If your fire pot is steel you shouldnt need to line it. If its cast iron i lined my champion with 100% clay kitty litter. Added some into a bucket and crushed it a little with a 2x4 (be careful not to break the bottom of the bucket) add watter and mix it up. Add water slowly  until you get the consistency you want and start applying the thickness desired. I didnt use any ash just clay and water.

This is my forge. I will get pictures of it with the clay.

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Hey, thanks for the quick replies. Ok did more digging on the forum and Google in general. My soon to be forge is currently the remnants of an old propane grill, probably made of 18g or 20g steel, maybe even aluminum. It's a bottom blast design, I was basing it off of. Most of the threads and information I've gotten into suggest a fire pot being about 6- 10 inches deep, and as far as width I suppose it is really just relative to the work in question, but I'm thinking it would be more difficult to keep the coals hot if i use a very wide fire pot with a central bottom blast as opposed to a system blowing evenly across a wider area, so in my case is it better to keep the fire pot a smaller diameter? Just out of cutiosity do you or have you needed to patch any of the clay at all?

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I have not had to patch the clay. And as for the depth and size of the forge depends on the kind of work you want to do. The bigger and deeper the pot the bigger fire. Then come the blower issue. Big fire pot means bigger blower. But charcoal dosent need as big of a blower ad coal. The bkower on my little forge has just enough ass to run coal but way to much for charcoal and i end up choking it down to about a 1/4 throttle with a piece of paper over the air intake.  I personally havent found the need to have any bigger forge than this one. I kinda think it is ideal for making knives. On the other hand i have a couple other propane foges and all the stuff to build more to suite my needs.

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Ok thanks that's actually really insightful. I got a bunch of bentonite cat sand the other day so tomorrow or Thursday I will probably clay it. What dimensions are your forge btw? Does it heat the whole pan of coal? I'm just looking to avoid as much dead space as I can reasonably. 

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I will get some better pictures and dimensions but it is about 18"x18" and about 3 inches deep and you can control the size of the fire by air control. I can get a roaring fire if i wanted especially with charcoal!!! Maybe i will get a video of it running with charcoal. 

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Keep in mind that charcoal burns up relatively fast, it is relative to the amount of air you feed it, of course. So if you have an unnecessarily large fire, youll be wasting a lot of fuel, and adding more constantly. Keep your fire large enough to do with it what you want, but with charcoal, ive found it more important to keep your fire efficient.

Remember, theres no sense in heating more metal than you can hammer on before it cools down. 

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  • 2 weeks later...

Well I fired up the forge this morning and attempted to make some tongs. Unfortunately I failed in that regard but,  learned from the whole experiance. If I had something to drift my punch through I may have came out with half, but that's for next time. So all of this has left me with some questions, being that there was a lot of slag, this is due to the silicate in the charcoal correct? And not the clay? How can I diminish this if at all? And when I went to remove the slag it pulled out some rather large chunks of my clay lining, what would cause this? Oh and is it accurate to say that the color of the heated metal in sunlight is dulled a few shades as opposed to being viewed in a dark lightning? Sorry for the barrage of questions, as always I appreciate any responses. As soon as I saw that piece of metal glowing orange I had the biggest grin, still stoked for all of this... see what I did there.:D

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The "slag" is probably scale and is caused by too much oxygen in the forge. Probably caused by an oversized blower or having your work piece too deep in the fire. Try having the steel a little higher in the fire. What kind of blower are you using? Here is a picture of my forge.20180310_101836.thumb.jpg.1dde2cc1ee73d1872f1ce290674ca509 (1).jpg20180310_103846.thumb.jpg.977f264f26fddc100e7de983f2d204f6 (1).jpg20180310_103109.thumb.jpg.0fb537024116301c0cdddb1dc681618c (1).jpg

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And yes hot steel looks very different in the sunlight. What may appear to be gray in sunlight may actually be a dull red in the dark.

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There was scale on the metal I was heating, but the slag I'm thinking many people call it clinker, I've heard it called dragon poop, haha and after today I can see why. But that's what I was asking about. For a blower I am just using an old hair dryer, it's possible it could just be blowing too much I was often piling charcoal on there. As far as the lighting I took some heated pieces over to the shed to see if there was a noticeable difference, and it did seem to be much brighter of shades in the shadow as opposed to the open light. I know in the sunlight the brightest the steel got looked like a bright yellow orange, which now reflecting on I'm sure was much hotter than I thought. I'll put some pictures of my set up up here later when I get off work or have time in the morning. And I did end up I guess melting about an inch of the steel off it stayed in a solid piece just came off the larger bar. After that I was trying to keep it little higher to moniter it easier. Thanks Jeremy.

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Hmm good to know, then what ever is  I try to get a picture of it too for verification. Would the ashes melt together? The rebar I was using stayed solid, except for the end that broke off but that was after the thick globules of brown stuff started sticking to everything.

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It could also be small bits of your clay lining that are melting from the high heat, a forge gets hotter than you think, and when pieces of clay get knocked loose they can melt.

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Sounds like there is sand in the clay, and yes, that will melt into a glassy goo.  And also yes, bright sunlight will throw off your color vision of hot steel by several hundred degrees.  That's why blacksmith shops often resemble goblin caves, it's not that we can't take the light, we just need to see the steel colors properly!  :lol:

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3 hours ago, Jeremy Blohm said:

100% clay

Not necessarily.  It is "100% natural clay".  That could mean it is "100% natural" and it is "clay".  I would bet anything listed as "clay" can have a certain amount of "non-clay" (e.g. sand) andnot need to have that specified.  It could even be a fairly large percentage.  

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Right on the back of the bag it says 100% natural ground clay. I havent had a problem with it at all. Not the slightest hint of anything on the blade when im using my forge.

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I would say it is safe to use. If you have anything with some kind of scent or anything else i wouldnt use it.

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