Flagstone forge

[CEmory]

I am starting my forge build and am having to do things on the cheap, but I have a bunch of flagstone that had been serving duty around the graden beds and figured it would serve as a good foundation on which to build. The location is odd as I want the rear to be protuding off of the poured slab of our former garage to both save space and add a little something to the small building that I plan on in the future. Now, to save a bit of stone (cuz I don't really have alot of large, thick pieces) I chose a spot on the back side of the foundation that had several inches of hill where sediment had built up against the siding, likely from the former's dog digging back there cuz it was a fairly large, if low hill with a big ol hole next to it. This dirt is obviously the same dirt they had hauled in to lay the nice large slab I have here because it gets nice and hard after a good soaking with the water hose and dries xxxx hard. I went ahead and sorta framed out what I wanted on the slab in the stone then filled it up with the same dirt cleaned free of most of the debris and packed it down until everything was level with my original hill that I had leveled beforehand and gave it a good soaking. My frame of stone is currently six to eight inches deep and composed of a single 'wall' of large stones set directly on the slab and ends at the original dirt hill. I plan on simply laying another frame on top of the original hill and building up a short wall to fill with some more dirt. After I get to a height I like, tapering inward a bit as I go, I'm going to burn a bunch of stuff in it to get a bunch of ashes and pack them all in there. I'm having to work with all natural materials, red clay mixed with ash and sand will be the morter for this stage.

So my questions are, how am I doing so far? Should I have made everything level with the slab, or even built up a more proper foundation for the rear 1/3 that will protude off the slab? I'm 6' and want this to end at perhaps hip height to the be built up slightly further with the rest of the forge, is this too high in the end? And either way can I fill this 'base' halfway with dirt or more then pack ashes in the rest? I want it to last as long as possible, so should I mix something with the ashes to make them firmer and thus more durable? Maybe lay down a gravel base before adding the ashes, too?

Could I use the flagstone to build up the forge itself, enclosed save for the front with a short-stacked chimney towards the rear, not too wide, 8 inches, maybe 9 square at the opening and long enough to eventually get a sword into. Should this be bigger? I'm going to put with some sort of refractory on the inside, but again have to do it natural. I have a bunch of broken ceramic tile that I was thinking of turning to powder and mixing with my clay/ash mix, or if I could just use some of the bigger chuncks to line it I will, but if I HAVE to buy some portland I guess I can sneak the boss' wallet out of her purse, lol. NOT! But I'll tell her I'll make her a steel rose soon and maybe I'll get points. :)

What I'm worried about is the stone cracking. I've flintknapped in the past and heard that while this stone is not really favored for it, with a good cooking it can become glassier and thus worked with patience. Should I maybe do a slow bake on the particular stones making up the forge to toughen them up a bit before building? There will be a small ledge to the left side as well to accomidate a Japanese style bellows and maybe a little more. This will be made of the same stone of course, ending at the forge wall and it will be a side blown forge. Could I form the airways out of something I could remove and mold them out of my refractory, whatever that ends up being, leaving the hollows when I removed my mold? And lasty, should I form a 'ditch' for lack of a better word atm, for a firebed or should I just leave the bottom of the forge flat?

If anyone could maybe supply a picture or two of some old (or new, lol) stone forges that would be awesome too. I've done searches, but only found a couple and they were not so great.

And as a side note, working with this stuff is hard! I've had ALOT of trouble with shaping it because it flakes off so easily, being formed in layers, and I don't have access to a diamond blade to cut the stuff with. I'm going to try to score it with a regular saw, but I'm afraid I'll just end up ruining a blade. Good thing I have one on its last ropes!

Thanks in advance for any suggestions.

~C

Edited June 21, 2012 by Glenn

[Bentiron1946]

I would sure slow bake it! Flagstone can hold a lot of moisture and if it has been in use in the garden I'm sure it has a lot of moisture in it. I have not use flagstone but regular fire brick that had a lot of moisture in it and didn't allow for adequate drying time nor did I have just a regular kindling fire to dry it out slowly but started off with a really hot fire. It was a xxxxxxx disaster! I not only had the fire clay popping but I had the fire brick flying apart from the steam generated inside of them. So I guess the answer would be, yes you can build a forge out of flagstone but there will problem, it is not the best of refractory materials to use. A plain clay soil could work better than the flagstone. Moisten it enough to pack in place, light a kindling fire for a slow bake, clean out ashes, repack cracks that develop, relight kindling fire and then start adding coal and start blower. I have used this for a forge liner before and it easy and reliable. And it is also easy to repair, the dirt is in your yard most of the time.

[ThomasPowers]

So part of the system on a foundation and part on no foundation? 1 wet year and you can have trouble!

I think you are trying to spend too much money on this over time rather than electing to do it right the first time...

[CEmory]

not spending money on it lol, wish i could, but yeah, I should just bring it all inside, was just trying to save space in the future shop and this wasn't really meant to be entirely permanent, just hardy. I'll just build the rear extra thick and have it serve as part of the rear wall instead. This was a quick attempt to get the smokestack outside without having to go through the future roof, so if I could still manage that without having to buy anything for a foundation atm it would be nice and we are coming into our dry season in texas so rain likely wont be a problem, though it has been drizzling on and off all of today. This will be replaced with a more proper stone forge at a later date, hopefully by winter if all goes right with the stars and planets and all that stuff that seems to effect my bank account <_< .

I would sure slow bake it! Flagstone can hold a lot of moisture and if it has been in use in the garden I'm sure it has a lot of moisture in it. I have not use flagstone but regular fire brick that had a lot of moisture in it and didn't allow for adequate drying time nor did I have just a regular kindling fire to dry it out slowly but started off with a really hot fire. It was a freaking disaster! I not only had the fire clay popping but I had the fire brick flying apart from the steam generated inside of them. So I guess the answer would be, yes you can build a forge out of flagstone but there will problem, it is not the best of refractory materials to use. A plain clay soil could work better than the flagstone. Moisten it enough to pack in place, light a kindling fire for a slow bake, clean out ashes, repack cracks that develop, relight kindling fire and then start adding coal and start blower. I have used this for a forge liner before and it easy and reliable. And it is also easy to repair, the dirt is in your yard most of the time.

This is quite helpful too. So you dont mix your clay with ash or anything? Always heard you should when going this route, but I'm always open to a new way. If anything I can use this liner until I can get my hands on some firebrick.
Tell the truth this thing's gonna be a big ol' 'HEY OVER HERE SIGN' until I get a building around it so in a vain effort to keep the neigborhood happy I wanted this to be......pretty :ph34r: