Can a forge be built from rammed earth?

[kiltedpiper]

Got a question for the collective. I did a mild soil study in my back yard and it has a high density in clay. To say the least it is much akin to concrete. So with the addition of some concrete mix and some silica, would it be possible to make a forge out of rammed earth? I have seen its structural capabilities as the same as a concrete pillar...or a little less depending on soil quiality. Or has anybody tried?

[Steve Sells]

Didnt you notice the section above called JABOD - Just A Box Of Dirt?   but leave out the concrete you dont want that in there

[George N. M.]

You could also mix in some straw and make adobe bricks.  Either rammed earth or adobe would work fine as a forge base.  I'd go with adobe to avoid the ramming step.

"By hammer and hand all arts do stand."

[Frosty]

Sure but leave the Portland cement OUT of it. concrete isn't what you meant and is dangerously unsuited for a forge! Seriously CONCRETE spalls, the moisture that turns it to stone turns to steam, expands and blows HOT, SHARP pieces all over the place. NO CONCRETE!  Leave the Portland cement out for the same reason!

George and I differ about clay type forges. Adobe is wet and easy to install but tends to shrink check as it dries in a forge. It doesn't check much in a building but it dries slowly enough it can shrink without cracks. 

My preference is a mix of about 2 parts sand to 1 part clayey soil with JUST enough water it will form a hard clump when squeezed in your hand. Ram it into the forge table till the mallet bounces, scrape and shape to suit. Adding white wood ash to the dry parts will make a binder that is not heat susceptible like Portland cement. 

This  rammed forge table and fire pot won't shrink check as it dries or with the rapid heat changes of a forge fire. 

I suggest you just build a JABOD it's easy and fast enough to make even if you have to buy a little lumber if you can't scrounge some and works a treat. It's THE forge for charcoal fuel.

Frosty The Lucky.

[George N. M.]

Frosty and my difference of opinion about adobe and rammed earth may come from the fact that he lives in a more humid climate where it takes awhile for things to dry out and I live in a semi-arid climate where things dry quickly.  Of course adobe has to be DRY before it is suitable for a forge.  The only question is how long that will take.  Here, I suspect that it might take a week or 10 days drying in the summer sun.  It might take weeks or months in much wetter Alaska.

I was visualizing a forge built entirely of eath in one form or another, similar to a brick forge, not just lining a metal or wood pan.

I suspect that Piper, being in Boise, ID would be in a pretty dry climate.

"By hammer and hand all arts do stand."

[Frosty]

Good points all George but I based my rammed earth forge "recipe" on long ago green sand casting which is fine sand and bentonite. The trick with the moisture content is to ram the mold hard enough to hold shape and detail but be porous enough to allow steam to escape when filled with molten metal. 

I'm betting if you include sand in your adobe recipe it'd dry much faster and be fire ready before it's completely dry. The sand provides porosity and voids that allow the fill to move without cracking. The voids also enlarge as the moisture leaves instead of pulling a straight clay apart. 

Drying pottery clay can be a precise and tricky process, I remember cabinets we let pottery dry in before bisque firing. 

Regardless how you do it the answer is YES you can indeed make your forge table and fire pot or my preference a duck's nest from dirt. Clayey is best.

Frosty The Lucky.

[JHCC]

I think kiltedpiper is asking about making the entire forge from rammed earth (much as one might build one from masonry), not about filling a metal forge pan with it. That is to say, the question is whether or not could one build the whole structure by ramming a slightly dampened mixture of clay, sand, and cement into a removable form such as one would used for poured concrete.

I would say Yes.  I would also say that using Portland cement as part of the mix for the body would be entirely appropriate, as it gives rammed earth its strength and structural integrity. That said, I would recommend finishing the top with a layer of clay without the cement, anywhere that would be in contact with the fire, to avoid the risk of explosive spalling of the cement. 

If you do go down this road, you’ve got the standard design choice to make: side-blast or bottom-blast. A side-blast would be pretty straightforward, and you could just build a form to the outside dimensions of the forge and fill the whole thing up as a solid block. If you go with a bottom-blast (either with an integral firepot or with a manufactured ones  that you’d drop in from above), you’ll need to make the form with removable centering to create the arches underneath, thus:

 

[Frosty]

That could be made to work. I think I'll wait to see what the Kiltedpiper  has to say before I dive into more possibilities.

Frosty The Lucky.

[anvil]

Thats the way I read it too, that he is building a forge. 

I would find or buy a good rectangular bottom blast cast firepot like from Centaur Forge and set it in while you are building it. And put fireclay or castable refractory about 6" or so between the rammed earth and the cast firepot. Why bottom blast? I like it better because its easier to remove ash and clinker.    Lol, You either need to break your fire down to clean the ash, or you need a hole and a clinker ball in the bottom to remove it. An ash dump is best in my opinion, so if ya got an ash hole there anyway, might as well bring your air in thru it.    

[Frosty]

Not in a side blast trench you don't, all the crud just scrapes right out.

 Frosty The Lucky.

[anvil]

Yup, and breaks up your fire.

[Frosty]

We must clean a fire differently. I push the heart to one side of the tuyere, rake the crud and move the heart back. Then again I've only used a forge with a clinker breaker a couple times so I probably don't know enough to compare. I know it disrupts the fire cleaning a duck's nest or a firepot that doesn't have a breaker. The duck's nest less so.

Frosty The Lucky.

[anvil]

A clinker breaker is like a night to day upgrade if you haven't used one. At its simplest, Rotate the handle once or twice and the ash is gone. Fire is not disturbed. Thats why I don't use a side draft. Clinker ball or breaker is kinda misnomer. Its more of a way to get rid of ash and fines, which happens a lot during a forging session. So not disturbing the fire is pretty important. 

I've actually never seen a firepot that doesn't have one as part of the design. It's my only gripe with a JBOD. I can't imagine not having one.

I'm pretty sure I know how to use and maintain a side draft forge. I don't know any other way than to raise or move the coke then put a rake in under the coke and drag the ash and fines out twards you. 

 

 

[JHCC]

In a traditional side-blast forge, the ash and fines end up becoming part of the dirt fill, and all you need to do is hook out the clinker. Because that sinks down through the fire and collects underneath the nozzle of the tuyere, all you need to do is kill the blast, give it a second for the clicker to consolidate, and then pull it out from under the fire with a thin poker. Easy, peasy. 

That said, I have used bottom-blast forges both with and without clinker breakers, and with is definitely better. 

[Frosty]

I've never used one long enough to get to know one, I DID like how it acted as a fine control for the blast.

About the original question, I'd still like to know just what Kiltedpiper had in mind. I've made many field expedient forges when I was a driller. One of my best was on a sandbar on the Resurrection River where we were camped for almost 2 weeks. Just below there was a LOT of iron and steel in and around the river, it was an emergency dump site after the 64 Good Friday quake. Anyway it's good hunting for steel and iron salvage. In maybe half an hour I had a couple hundred lbs of good forging stock. Unfortunately the sand bar made a pretty poor ground forge, side blast as I learned later. Soooo, I collected a bunch of rod, lots of rebar, some sheet and boulders from away from the river. I drove the rods into the sand bar till they were reasonably solid, laid boulders in the gaps and filled the center with sand. I built it up to maybe 3' +/-. I'd embedded a length of broken NW casing in the thing the low end facing up river, into the wind. I piled rock over and around the top of the casing and called it a forge. I rapidly discovered burning wood down to coals meant you couldn't get within 10-15 or your clothes smoked. I scrounged a 15gl grease barrel, cot the ends out and made a opening to get to the coals. I tossed wood in the top and ended up finding more sheet to be a heat shield between the barrel and I. 

If I'd had clayey soil or even some to mix with the sand it would've been an easy build and looked more like a traditional masonry forge. (Sorry about that long ramble but I really loved the Resurrection River forge it worked so danged well.) Heck it was that trip I lucked into a machine shop / chandlery that was liquidating and I scored some excellent booty including a 150lb Columbian anvil and passed on the 1,200lb Fisher anvil. I drove my pickup back on my day off to pick up what I couldn't fit in the state truck.

Making a convenient height forge from rammed earth would only take time and patience and it'd let a person get creative. For example the Resurrection forge would've had a wind scoop built into the forge instead of a piece of pipe and sheet metal scoop. A deflector blast control and you could store things in the cavity. 

If I still lived in the SW I'd make enough adobe bricks to make a more traditional masonry forge with side draft hood/chimney. It'd need shelter from rain of course but that's easily within scrounge range. Pallets and old tin / plastic siding is EZ PZ. It wouldn't have to be a full blown shop, just a weather shield for the forge itself. Of course if you have time for it to cool a tarp cover would do. 

There are so  many ways to make a "fire place" forge, I'm in danger of getting carried away here.

Frosty The Lucky.

 

[JHCC]

Getting back to rammed earth, here's a documentary film from 1990 showing construction of a rammed earth building in Spain:

 

[anvil]

My interest in rammed earth came from "The Mother Earth News" mag shortly after getting out of the service. It really grabbed me and led to a strong interest in adobe. Three other styles I got grabbed by were swedish cope log, timber framing and rock. I built a log home, did a stone, iron and log shop and got involved with timber framing via my smithing. My daughter had me come to New Mexico to build an adobe, log and iron home for them but she and hubby couldn't get past the design stage. Dang, close for adobe, but hey,, 

So doing a rammed earth forge is very doable and would look good. 

My experience with a side blast leads me to believe that it works as you say and works well if you are forging a few hours a day and when you return, you clean out your forge and start new which is a good practice. But when you have to break your fire down multiple times a day to maintain a clean fire, there lies the problem. Coke still is on the bottom of the firepot and below the nozzle. This coke burns and it gets mixed with the ash and gets carried up onto your work. If your coke makes a good coke ring, you can lift it up with your poker and get your rake under the coke and rake out the fines. However, with coal that has a high % of ash and doesn't make a good solid coke ring, you are just plane sol.  

My other critique is the quality of the actual fire ball. A bottom blast with a good triangular shaped ball will channel the air outwards twards the fire pot walls and not straight up.This means the oxygen is not directly on your iron but burns from the outside in making a real nice consistent heat ball envelope surrounding your work and the ox is consumed long before it contacts your work. The air from a side blast on the other hand, comes horizontally out the nozzle and directly comes  into contact with your coke. So instead of the sloped walls, the irregular shape of and spaces inbetween the coke determine the relatively helter skelter flow of air which makes a far less consistent fire ball. These are certainly small details, but like they say,, the devil is in the details and these differences really become evident with use. Personally I think that the interest in side blast is because this type of forge is rare so its fun to play with. However, I suspect that there is a huge predominance in bottom blast type forges for a good reason.   

[Frosty]

Side blast forges are rare? Hardly Anvil, side blast has been in use since humans have been forging hot metal and it's still in use through the majority of the world today. Bottom blast forges are relatively recent and much less common. Most people in the world who rely on "traditional" blacksmithing do it the way their mentor's mentor's mentor . . . did it. Often with a pipe poking into a ring of rocks with a fire burning into it and village kids supplying the blast with a goat stomach bellows or maybe a bunch of grass on a stick pumping in a bamboo tube. Really old school blast is supplied with fans on a paddle, say a large leaf. 

Side blast doesn't mean a trench forge like a JABOD, you can buy a brand new side blast forge with a water cooled tuyere in the UK. Do a search for "Greystone Forge" (dot com) they have a wide selection and will custom build to suit. The blast is parallel with the forge table directed slightly downwards maybe I don't recall. The blast enters the forge through the "fire back" which is the table face of a water tank, against which you build and manage your fire. Choosing which zone to place your iron is really easy, you can see the entire heart. Move it too close to the tuyere nozzle is oxidizing, in the heart is neutral goodness and farther it's carburizing. 

A trench forge works pretty much the same way, the blast spreads against the far side of the trench and you determine where you want your steel the same way you do in a fire pot. Too close it burns, just right and it's neutral goodness, farther out or higher and it's carburizing. The fire disperses sideways in the trench more than it goes up so you can distance your work by placing it higher or farther horizontally. The big difference between side blast forges and bottom blast forges with a fire pot is your work placement isn't limited by the depth and width of a firepot.

Both types have advantages and disadvantages, but both will heat your work effectively and quickly. The main difference is the experience of the operator. (blacksmith)

You can lift the clinker ring and pull it out of a bottom blast. Yes? What makes you think you can't hook and pull the clinker from a trench or old school side blast? It takes no more learning to manage either. 

Brother you're falling into the same trap everybody does now and then, You're imagining problems that don't exist because you aren't familiar with using one.

Been there, had similar thoughts until I learned different about a new craft.

Frosty The Lucky.

 

[Irondragon Forge ClayWorks]

5 minutes ago, Frosty said:

you can buy a brand new side blast forge with a water cooled tuyere in the UK.

Or build a very nice one like JHCC did a while back.   New side blast with water tuyere & bosh (pic heavy) - Solid Fuel Forges - I Forge Iron

I can't control the wind, all I can do is adjust my sail’s.
Semper Paratus

 

[George N. M.]

Not strictly on topic but regarding adobe/mud bricks I read an article this morning about scientists being able to extract plant DNA from the vegtable material in a neo-Assyrian mud brick of the 9th century BC.  Here is the link:

https://www.thehistoryblog.com/archives/68106

G

[JHCC]

2 hours ago, Irondragon Forge ClayWorks said:

a very nice one like JHCC did a while back

That was a lovely forge, and although I no longer work with solid fuel, it served me well, and I was happy to send it on to a beginner to accompany her on her smithing journey. 

[anvil]

Well, Frosty, I appreciate your input, but will stick by what I said. I will qualify it and focus on the western world.  They are rare and really not used in the west very much. I'd say at least since the 9th century a bottom blast has been the norm. 

Thanks for the Greystone forge site. I checked it out and it looks just like the one JHCC made and was referred to. Nice to see that they are available. I think there are 5 or 6 folks who make bottom blast here in the USA. Do you happen to have any sources for others manufacturing and selling side draft anywhere? I'd be interested if you do. Yup, they all have the same problems I list above. I don't think I mentioned removing clinker in my posts above, did I? Didn't need to bring up the obvious.  I did mention ash, and removing it is the major problem as I stated. 

Do you really think having a fire that has different temps at different distances and unreachable depths from the inlet is a plus? Sheesh, my man, I'd much rather have a constant temp throughout that is changed easily and quickly by changing the air input instead of moving my irons around the forge for each needed sweet spot.  But hey, to each his own. I can't even imagine building a railing and not having a constant temp when I have 6-8 pickets in the fire doing tenons or whatever. That is my experience speaking, not to mention those I have worked with. I suspect that if a side blast were a better heat source, the great traditional smiths of our time would be using them as well as at ABANA conferences etc,etc. But thats just not the case. I'm sure there is a good reason for that, don't you think?

And yes both have advantages and disadvantages and these have no bearing on operator experience. It boils down to do the advantages of a side blast out weigh the disadvantages so that I ought to have a dedicated setup in my space, or is it better to just rig up a trench on the floor for the rare times I need the advantages and am willing put up with the disadvantages. Again an experience call. And yes, all the disadvantages can be dealt with, it just takes compromise of technique. 

Why shucks, I'd go so far as to say that if you canvassed all the shops in Alaska, dollar to a donut that finding working side blast would be slim pickins if any. 

No trap, Frosty, just experience and common sense. 

Having said that, If it is what you want to use, then go for it. They will do the job and certainly have a strong "cool factor". Also, with out a doubt they are perfect for unique situations, which is where my experience with them comes in. in these few situations they were great. And when the job was done, I filled in the hole on my floor and went back to my bottom blast. My purpose here is very simply to do what these forums are all about and that is to add info that may not have been brought up. So Frosty, if this info is causing you a problem, then hey, it aint the first time is it? Puzzles me as to why, but oh well.   

[JHCC]

1 minute ago, anvil said:

I did mention ash, and removing it is the major problem as I stated. 

That isn't a problem at all. With a side-blast forge, any ash stays in the forge and becomes part of the fill material.

[anvil]

I did mention how to remove ash above. As for not cleaning it out because it becomes part of the fill material,,, well,,, doesn't the fill material grow when you add ash? Its ash, not magic dust!    And it certainly, over a short time, will trash your fill if you don't remove it, or am I missing something?  My ash bucket gets filled every week or so with ash and other forge gradoo.    To my way of thinking, removing the ash is the best solution. Its a major part of having a clean fire, no matter where the air comes from. To me, ash removal and a dirty fire are the main problem with a side blast.

The best setup for removing ash from a sideblast that I've seen and used was a drop down door on the operator side of the forge. Drop down the door, raise the coke with your poker, and pull the ash out twards the operator with a rake. 

Again, my purpose is to show the problems you will encounter, not say don't use it. Your forge was a fine work, and I'm sure brought you much joy, as all hand made tools should. 

[Frosty]

I can't think of a time or forge type where ash was an issue. I should prove your point by polling smiths in Alaska as to what type forge is in most common use? Probably 8or9 in 10 smiths in Alaska, I'm familiar enough with to offer an opinion, use propane . That's growing in the interior too since the local "Tractor" supply stopped carrying smithing coal and the commercial coal mine doesn't produce or sell metallurgical coal for sale in America.

The guys still using solid fuel forges are switching away from bottom blast because of how much charcoal they waste. 

 

Frosty The Lucky.

Edited August 24, 2023 by Mod34
Personal remarks removed