Making steel (2)....the "Aristotle" furnace

I want to try making my own steel so, based on the specifications given by the Japanese swordsmith Sumihira, I built this oroshigane melting hearth furnace.

This simple vertical shaft furnace is used to melt scrap iron and steel, and in doing so, raise (or lower) the carbon content, hopefully to around 1.5% in my case. Make note that this furnace is for remelting scrap, NOT smelting iron from ore (maybe someday I'll give that a try too, but for now…). I'll give the particulars of this build in another post, mistakes and all, so those of you who want to give this a shot have something to go on. Everything I learn was originally shared on the net by someone else, so it's only fitting that I do the same. Successes and failures both.

For starters though……

After building my oroshigane furnace, I had some materials left over, so I quickly put together a smaller version, based on writings by Lee Sauder. A PDF of his original paper can be found on his website, along with some of his other writings. All are worth reading and it's thanks to his work that so many others are trying these archaic methods of steel production. He's the pro.

Lee Sauder smelting research

Aristotle furnace

Aristotle's steel

This “ Aristotle” remelting furnace is intended to be a quick and economical way to try making some steel and should be considered disposable. You might get 3-4 uses if you are careful but to try making it more robust rather defeats the purpose. You can slap one of these together and have it drying within an hour, a great afternoon project, for sure. Uses VERY little charcoal, one bag will last for multiple burns. If you've got clay in your yard, it'll cost nothing to make and it's super fun!

I've made three for these things now, but my success has been, ummm….not so good. Two aspects are important for this design to work. Clay and air. Last year, my friend Jeff and I tried building one of these but, living in Hawaii, we have no native clay here. What I did have was the clumping type of cat litter.

Clay

CAT LITTER WILL NOT WORK WELL AS A HIGH TEMPERATURE REFRACTORY!

Unscented clumping cat litter will reconstitute into a workable clay and is handy for lots of things, just not the extreme temperatures required to melt iron. At high heat, the clay starts to degenerate into a sandy powder. It shrinks a lot too, not what you want. If you have clay where you live, try that first ( it will likely work) but if you need to buy it, look for something with a high firing temperature, as close to a cone 10 as you can get. Lots of stuff will work though…..Just not cat litter, haha.

Air supply

Last year I used an old 12 volt air mattress inflator and it was fine. A hair dryer should be perfect for one of these small shaft furnaces and they are cheap and easy to find (if you can't borrow one ;-). A shop vac, set to blow, will be WAY too strong, but OK if you can throttle it down some.

Once your furnace is dry and up to temp, the steel making process only takes about 20 minutes. In my case, we were listening to the shriek of that inflator for 2 hours….WAY too long! We were melting down some ¼” rebar bundle wrap wire, no problem for this design, but something wasn't right. The iron bloom that formed in the furnace was stuck fast, so after smashing the stack to get the metal out, you could see that the area of the tuyere (air inlet) had slumped, greatly restricting the airflow. We did make a blob of low carbon iron, though not what I was shooting for. No pics, my bad.

This time, still traumatized from last years howling mattress inflator, I grabbed a small 50 cfm bathroom ventilator fan and gave that a shot. I mounted it in a very sophisticated, waterproof and mobile containment (ie: Walmart bucket w/lid).

I added a ball valve to the 2” pvc tubing so that I can adjust the airflow down, handy for slow preheats or for using in the real forge.

50 cfm works for a small charcoal forge, but a 100 cfm fan might be a better choice if you are buying something new. They aren't the perfect choice for a charcoal forge in general, but they work and are very quiet. If you are forging with mineral coal, don't waste your time with these, get a real blower.

For this “Aristotle” furnace, I used a mix of Home Depot fireclay, perlite (for insulation), shredded bark (for strength), and mortar mix to help things set up more quickly.

Despite what you might find on the internet, mortar/cement is a POOR choice for high temperature refractory. It's just not durable and when those hydrogen bonds reverse at high heat, it changes back into powder. It will work, somewhat, but there are better choices. Simple sand and fireclay seems to work better….20/20 hindsight.

I dry and preheat the still wet clay by burning some scrap wood, then start adding the guava charcoal that I made a couple of years back. You might remember my charcoal making ventures from before, and I'm finally getting a chance to use some of it. I really need to start making pine charcoal again, as this Guava burns slow. I'd prefer to have both on hand in the future.

At the center of the stack, you can see some of the ¼” mild steel stock that I am melting down.

Trying to melt down, that is.

Ellie melts down some old copper pennies and pokes the steel into the hot zone…..

….while Renee snuggles Nago the pig.

And in the ancient tradition of iron workers everywhere, I give offerings of ale and try to melt some bottlecaps. The stick of wire just sat there, laughing.

No love…..needs more air.

More in a bit…..

Oroshigane steel (3)....."Aristotle" again

The small “Aristotle” remelting furnace that I slapped together was suffering from one major deficiency….lack of air. The 50 cfm bathroom vent fan I used just doesn't have enough “oomph” to get this thing up to iron melting temps, though we gave a mighty effort. Secondly, because I didn't give the furnace time to dry out properly, the poor thing developed some pretty extensive cracks as the clay shrank.

Step 1) Suck it up and pull out the hated air mattress inflator, who's devilish shriek haunts me still. I swear, the damn thing makes my tooth fillings vibrate, but it does move the air.

Step 2) In hopes of getting one more use out of this little disposable design, I wrap the stack with baling wire, then apply more clay mix to the outer surface. A little extra mass will make the furnace both more sturdy and add a bit of additional thermal mass.

Let's fire it up!

You can't see what's happening to the metal inside the furnace of course, but the character of the flame can tell you something.

Here you see that the stack is full of burning charcoal. The flame is thin, red, and of low intensity; it's time to add the metal to be melted.

The idea here is to put the metal on top of the pile of burning charcoal, then keep adding more charcoal to the top as the pile burns down. The metal will slowly descend, hopefully to melt into a viscous pile at the bottom of the stack. The entire process should only take 15-20 minutes. This time, I am remelting old steel and cast iron blooms that I've made in another furnace, just playing and experimenting right now.

What I want to show here is the flame character.

As the iron and steel reaches melting temperature, the color of the flame shows more of an orange cast and there is a substantial increase in flame intensity. The air supply is unchanged from the first picture, but the flame is much “thicker” now.

As the melt progresses, the flame gets more yellow in hue.

Most of my melts have produced diffuse and airy blooms, probably due to my lack of a good, strong air supply. This time, I am running the burn for a longer period, just to see what I get at the end. Occasionally, the sound of the blower will change, indicating that tuyere is becoming clogged with slag (waste), molten metal or whatever. This design allows outside access to the tuyere, REALLY handy when you need to clear blockage. Just rod it out and keep going…..

In any event, after about 30 minutes, the tuyere keeps getting clogged and, because this furnace wasn't built to last, it has developed a fatal fracture. The flame has shifted firmly into the yellow spectrum.

Post mortem analysis showed that intense heat of the flame had eroded the area around the tuyere, so much so that the airway was blocked and the bloom stuck firmly in place. The intense, yellow flame shows that the air is blasting directly onto the metal itself and beginning to burn off carbon. If you are trying to lower the carbon content of cast iron, that's a good thing, but here…..not so much.

And what is the result?

An interesting bloom of mostly gray cast iron with a few tiny spots of steel, and lots of oxidized steel and slag, all mixed together into a big mess.

I quench the bloom in water, then spark test before smashing it into pieces.

Most of the bloom crumbles into garbage, but one small area from the side furthest from the air blast fractures in a way that shows the crystalline structure of steel. Well….at least a tiny bit of steel.

I'm still learning here, but what I think I see is some gray cast iron with a few larger white cast iron crystals. The lightest color, fine grain material sparks like medium carbon steel, but most of this mess appears to be slag, the melted remains of the furnace wall itself. The old furnace has been crushed, sifted, and put into a bucket to soak for a while, waiting to be reused. Clay is expensive here!

Still exploring, more is on the way…...

Building a charcoal kiln #4

Part 4 of,

"More than you ever wanted to know about building a kiln for making bladesmithing charcoal."

I've got a few more things that I'd like to try.

For starters, my burn chamber is just a horizontal tube of tin. Once the draft gets established, the heat and smoke gets drawn into the coaling chamber nicely. It works OK, and you can't get much more simple than that, but when I look at the diagrams of the traditional earth berm kilns, you can see that the burn chamber is much more enclosed within the body of the kiln. 

The metal drum Iwasaki kilns that I've repeatedly referenced use a separate partial drum to serve as a burn chamber, and that's great. Mine could be improved though. See, the reason that I like the more enclosed fire chamber is that it looks like a smaller fire could be used, since the heat and smoke are more tightly directed into the coaling chamber. By reducing the size of the fire, we are trading a possibly longer coaling time, with the lessening of heat and the force of the flames.......At least that's my thinking.

The second thing that I've been wanting to test out.

The traditional kiln shows the wood being tightly packed and VERTICAL. I did the best that I could, and the back has a higher proportion of vertical, but.....This was a huge PITA, and I doubt that I'll do it this way again. Maybe with a rectangular coaling chamber it wouldn't be so difficult. We'll see what the charcoal looks like.

So here is my quick and dirty improvement to the burn chamber. That's not parallax error, it really is tilted.

The end that abuts the barrel lid has a mating flange that it sort of hangs from and also seals the join a bit, point being that it forms a tighter fit than before. Towards the center of the burn "tube" is the feed door, a 3-sided cut, bent down at about a 45 degree angle. The end of the tube at the left is still fully open. If it bears repeating, I'll take better photos next time. The description is hard to follow.

What I've made here is closer to being a top loading, horizontal draft "rocket stove", and it works so much better it's surprising. The separate air channel on the left let's you pack the fuel port totally full, without starving the fire of air. The burn chamber creates good air turbulence as well, contributing to better combustion. These simple mods make the fire much easier to start, it burns hotter, and it's easier to load the fuel charge (meaning you can cram it full and then just check back every 30 minutes or so to refuel). The slight incline to the chamber might help induce a properly directed draft too. It seemed that way, despite the visible flames occasionally shooting out the fuel port. 

It's still ugly and cheesy looking, but remember, I need to be able to whip this whole assembly out of the way in seconds, when it's time to shut down the coaling process. I can grab a stick and lift this nasty mess out of the way in two heartbeats. Also, don't forget that the galvanized metal that I am using gives off extremely poisonous fumes as the zinc burns off. Don't sit too close, not before making peace with your gods.

And the third thing.......

Right after my last firing, I was sitting around reading about Sumi-yaki (Google : 炭焼き ), looking for more tips and improvements I can make to the process. I found a couple of good ones. 

This is from a site making bamboo charcoal, slightly different, but essentially the same.

Charcoal making process according to the drum charcoal kettle is as follows.
1. pilot flame to burn and raise the temperature of
2. smoke up to 85-95 degrees and make sure that "it was deliberately fart" (strong smell) (0.5 to 1 hour)
3. fired to stop the pilot flame, to limit the supply of air, keep the temperature of the smoke (4 hours)
4. temperature of the smoke if promoted carbide begin to rise (2 hours)
5. temperature of the smoke misses the thermometer When equal to or greater than 180 degrees (one hour) is
6. smoke Open the internal cover Once colorless, do "Nerashi" (about 10 minutes)
7. Exit to close the air inlet and the chimney outlet (total of 8 hours)

When you get to the "Fart-smelling, yellow smoke phase", stop firing and cut back the air supply......huh.

I don't think that I've ever seen that referenced before, stopping the fire (the fart smell....everyone knows that. The yellow smoke has a large sulfer component, I think). The thought behind this is that once you get the yellow smoke going, the wood inside the drum has established a kind of oxygen deprived combustion, so any additional heat input only would be causing potential damage to the coal.
When you get into making traditional bladesmithing charcoal, you quickly realize that there is something missing in our body of knowledge, some little detail. Nearly everyone out there is making nasty, overcooked char. It's fine for the garden, but not as good in the forge. Everything that I've read has you firing the burn, right up until it's time to shut 'er down. Maybe this simple thing is one of the details?

Cutting back on the air supply will further slow the process of coaling, but it also gives greater control. Once you get to the yellow smoke phase, things start to happen ever more quickly. During my last burn, from YS phase to done only took a little over an hour. This time.....closer to 2 hours, but the rate of change towards the end of the process felt much more relaxed. I'm hoping that the charcoal felt the same too, nice and relaxed. We'll see.

So the yellow smoke for me and this Guava I'm coaling went on for quite a while, but essentially, I stopped fueling the fire and cut back the air a bit.

The yellow smoke phase is around 350*F at the stack. 

The partial brick at the front can be bumped either way to give enough air to keep the stack temperature rising.

 

I didn't really need to do anything though, just sat and watched the smoke.

We are getting close to shut down time. The stack temp reads around 500*F and there is still quite a bit of "white" in the smoke.

The amount of finishing time is one of the more important aspects that determine the qualities of the charcoal. Because I am using this for bladesmithing, I don't want to cook everything out. If I was using this for an indoor hibatchi or a charcoal heater, I would try to cook the charcoal until it was as clear as possible.

I guess that it goes to show just how divorced from the mainstream I am but.....it just occurred to me, the number one use for real charcoal is likely to be for grilling a barbecue, haha. Would you believe that I've not tried that yet?!

Wow! Get a life, kid!

Here is where I shut down, nearly 800*F at the stack.

If you compare the smoke to the prior pic, you can see that most of the "white" is gone. The time interval between the two was approximately 15 minutes.

I dragged the firebox out of the way, piled up bricks and dirt to shut down combustion, capped the stack and called it a night. 

So what do we get this time? Trash or treasure?

Hmmmmm......

I'm thinking trash. Where does all of the wood go?! The barrel was packed as tightly as I could get it. Lots of ash......

Overcooked.

Oh well.....it all burns, right?

I grab the shovel and sieve to start cleaning up, but this stuff doesn't shovel. Just past the overcooked stuff are sticks of solid carbon, and they aren't falling apart like the other charcoal that I've made.

Almost the entire burn looked like this......sticks, magically shrunken and transformed. 

It's too bad that the bark is still on the sticks, because that thin outer layer affects the resonant qualities. I've finally made the "hard" charcoal, paradoxically known as "white" charcoal, or electrolytic charcoal. These carbon sticks are now conductive to electricity. The light was pretty flat, but you can see that the charcoal looks silver, not black. Cool, huh?

I don't think that this would be considered true "white" charcoal, but it's getting close. This charcoal kiln is definitely capable of getting up to the 2000*F needed for complete carbonization, and I've been wanting to attempt the making of the "white" charcoal, but to get it right, I would need to open the barrel at the finish, then quickly smother the charcoal. Scary! The burning charcoal gets buried in old wood ashes.....ironically, something that I don't really have much of, haha.

This charcoal is really starting to exhibit the resonant qualities that I find so interesting. The water being completely driven out of the wood, making the carbonized cells ring like bells, each stick like part of a strange looking wind-chime.....I don't know, but it's neat to experience, charcoal that sings.

The resonance is dampened by both the outer bark layer and the amount of wood shrinkage within the stick itself. These didn't ring well.

As you'd expect, a solid bar of carbon rings clean and loud, while one that is covered in tiny plates of carbonized bark – which also resonate, but at different rates/frequencies– sounds flat or muddy.

These sound like tuning forks.

You only get a couple of whacks before some fracture occurs and the stick breaks in two. Some of the smaller stuff must've been fairly dry when they went into the kiln, because they showed no shrinkage splits at all, just solid carbon. When they break, it's with a super high pitched *TINK* that hurts my ears a bit. Some of them shattered forcibly, like a candy cane.

Towards the rear of the kiln, in the area of the vent stack, the wood barely even looks like charcoal. It has a brown hue, but it's not undercooked. There was also an iridescent blue in spots, some strange chemical compound flaring off, I guess.

 

So, at the very bottom of the barrel I laid four sticks full length, and of the entire load, it was only these sticks that didn't fully carbonize. Everything else was fully cooked, through and through. 

The verdict is in. 

I deem the charcoal kiln a success, though my firing procedure could still use some refinement. This kiln design is far and away the easiest and most reliable way to make high quality blacksmithing charcoal, at least compared to what I've done in the past. I'm having a hard time restraining myself from burning all the time, I just love opening the kiln up, seeing what has been created. Maybe it's because good charcoal is such a rarity? I don't know, but I just love it. 

A big question remains......is this charcoal any good? I am following my interests here, doing this just for fun. I mean....I still need to build a fuigo and small forge, I'm not even prepared to test this stuff properly. Right now, I'm learning the art, getting to know the kiln itself. I'm just seeing what *kinds* of charcoal I can make, and I'm not worried about whether or not the stuff burns hot/cool/too slow/fast, whatever. This batch ended up very "hard".... fun, but not what you want for forging, exactly. 

For forging you want the softer "black" charcoal, not this hard "white" charcoal, at least that's my understanding. When I was using my home made charcoal before, I was using the soft, crummy, and overcooked charcoal for lower temperature work like quenching and tempering, and saved the best hard pine charcoal for welding. It was soooo much nicer to work with, but it was also touchy, too. Get my timing off, forget what I was doing for just a moment and I'd start to hear the metal breath....then hiss, the sound of the steel burning. The charcoal that I made from rotten cedar deck boards could also reach welding heat, but it took MUCH more effort. Not beter/worse, just different. It should be a relatively simple matter to make a variety of slightly differing charcoal that will be task specific. 

Hopefully when Mark Grable reads this, he will be able to comment on what the charcoal was REALLY like, the charcoal that Yataiki preferred for forging his saws. I've got so many questions.......

• Red pine for forging, so I've heard, but were there different qualities that were used to differentiate? I can imagine opening a bag o' charcoal, sorting through the sticks and making different piles.....Chopping into ever smaller pieces.
• Is there anything that must be avoided, when choosing? Different species would burn differently, but also might introduce a chemical component that would be good....or bad.
• What am I obviously missing here? I mean....this is what I've come up with after watching a handful of YouTube videos, written anecdotes and allusions that I've found, and my own slight experience. But mostly this is the product of inference, experiment, and some guessing, haha.

And of course, there is the question of tree species. For all I know, guava might be a terrible bladesmithing charcoal.....I guess that I'll find out. This wood is still fairly wet, but surprisingly, it doesn't seem to matter much. Using dry wood must speed the operation some, but that might not be a completely good thing. This wet wood is shrinking dramatically, and shows many cracks and fissures. That keeps it from being used as part of a totally kickass Halloween themed windchime, true, but it also means that it is easier to split. The hard and solid ones are harder to break.....kind of loud too.

That a person can make a simple little charcoal kiln out of an old paint can, make some char, then start burning steel.....needing only a armfull of bricks and an old bathroom fan (and the paint can).....That's freakin' cool.

I've already got the kiln started on the next batch, this time loaded with all of the sticks lying flat, easy as can be. If anything strange happens, I'll let you know. If you know something that I don't......you let me know, OK?

Build a charcoal kiln part 3....The first results.

 

 

So I built this charcoal kiln to make proper bladesmithing charcoal.....If you want to see it from the beginning:

• Part 1
• Part 2

It's ugly, I'll grant you that, haha.

 

 

 

How did yesterday's burn work out?

 

Not the greatest I've made....

 

 

.....but not the worst, either. It looks badly overcooked. The barrel is only half full, but started out being packed.

 

 

Given that this was a newly constructed kiln, surrounded by wet grass/clay insulation (didn't work, BTW), and filled to the brim with wood that was far from dry....my expectations were low. I was anticipating a lot of undercooked stuff though, so go figure. This was probably a worst case scenario, so the results are encouraging.

 

My only real successes in the past have been using a 5 gallon retort style kiln. I've cooked in 55 gallon drums a few times before, but that only resulted in badly overcooked or badly undercooked charcoal. Certainly nothing approaching a consistent result, anyways. What did I get this time?

 

 

The first shovels don't look so hot (no pun intended). This ashy, shrunken and fractured look is overcooked. Too much heat, over too long a time period.

 

 

 

 

I sift out the fines using a nominal 1/2" mesh.

 

When I first opened the barrel, it looked to me as though much of the wood had been reduced to ashes –generally that's due to having an air leak somewhere– but as I am sifting, I'm not really finding as much ash as I had thought.

 

 

I do find a couple of pieces that aren't fully cooked. This chunk is 1/2 charcoal, the other 1/2 still a little bit brown.

 

 

You can still see the holes in the wood, tunnels left by beetle larvae. So cool!

 

 

Here is a perfect example of overcooked charcoal. Spongy looking, soft rounded edges, and a gray cast to it.

 

 

This is charcoal that has had all of the volatile elements burned from it, not really what we want for the forge. It's great for the garden though. I am surprised how little there is of this. Only 4-5% of the total, if that. I got similar results when using my 5 gallon retort.

 

 

Most of the charcoal came out looking like this. A perfect piece is on top, a slightly overcooked piece below.

 

 

The perfect charcoal breaks cleanly with a crisp *snap*. You can see how fine grain this Guava is. That is another variable to this attempt, I've never cooked a hardwood species, much less Guava. I've only used softwoods in the past.

 

 

A before and after comparison.

 

 

 

 

One of the aspects that I love the most is how little the wood is affected by a proper coaling process. If done well, the charcoal product will look exactly like the original, just shrunken and black after having all of the liquid components removed. The Japanese have turned this into an art of sorts, converting all sorts of things into charcoal themed displays.

 

 

I recognize a pineapple and a sea urchin, but the other stuff? Is that a lufa sponge?

 

 

My guava charcoal isn't that pretty, but you can see how many of the sticks had fissured, peeling bark when they went into the kiln and still have it upon coming out.

 

 

 

You can see evidence of the larvae tunneling underneath the bark. I just love this stuff.

 

 

It's hard to tell from the photos, but the charcoal itself has a silvery sheen to it, and it rings slightly when tapped. Pouring the charcoal into the bag, it has a musical sound to it.

 

 

And here is the yield. A small 4 lb bag of fines (mostly the small fragments of bark that fell off of the sticks), and a large bag of decent charcoal.

 

 

This Guava charcoal is MUCH heavier than the pine and cedar charcoal that I am used to. I would guess that the bag weighs around 70lbs, more than the bag can withstand in any event, so somewhere around there.

 

The small bag of fines can be crushed further and used for the bed of my forge, added to the clay for yaki-ire, used as a component of the welding flux, or just spread in the garden. Nothing is wasted.

 

 

Here is the barrel after shoveling out the interior. I took no special care here, just scooped out the charcoal, but my point is that there was actually very little ash produced, far less than I was expecting.

 

 

So in retrospect, the yield wasn't as poor as I had initially thought. The cooked charcoal is dramatically reduced in diameter after losing all its water, and also had settled quite a bit. It's hard for me to guess at a yield, but based primarily on the amount of ash I saw.....jeez, 80% maybe? 

Another good thing about proper charcoal.....it's clean. Well, kinda clean.

 

 

Despite having shoveled out a whole drum of char, screening it all and bagging it, my hands are barely dirty. My feet are still clean! It's nice stuff.

 

 

This particular batch of charcoal doesn't have the clear pure *ring* of some charcoal, but had I started with dry sticks to begin with, I suspect it would. The next batch (I'll probably start today....I'm a charcoal junky, haha) I will shut down sooner, earlier in the blue smoke phase, so we'll see how that affects things. The kiln is dry now too, not buried in wet mud. That should help. This charcoal will be fine to use, but I still want to do better.

 

Another improvement will be to construct the fire chamber to be more like a self feeding rocket stove, with a tilted or vertical entry for the fuel sticks. Put gravity to work for you, right? Nothing too fancy though, because you need to be able to seal the coaling chamber quickly.

 

So, a success! If you are into traditional blacksmithing and need some fuel, this works well. We've got tons of downed trees sitting here that I need to clean up, nearly all of it being thin, invasive guava that everyone else hates. I haven't used the guava charcoal in the forge yet (still haven't built my forge even, so I guess that I better hurry up, huh?), but this should work fine. There is a never ending supply of free guava here.

 

This is a great way to use what many people view as waste, and that's a huge positive in my book. Cut the tree, and what isn't suitable for lumber gets turned into charcoal. The smallest twigs and twistiest branches are used to actually make the charcoal, while the leaves go into the garden compost.

 

The only real problem that remains is the noxious smoke thing. Maybe we can devise a scrubber for the vent stack. One of the more common uses for the Iwasaki kiln is to capture the "Wood vinegar" distillate, used for lots of different things but I'm not really familiar with that side of stuff. Essentially, the smoke gets funneled into a long cooling pipe, then condenses back into a liquid which then is collected. Something to think about. It might be worth a shot.

 

 

My charcoal producing kiln is not really an original idea (nothing is, right?), but is loosely based on a traditional Japanese coaling kiln.

 

http://blogs.yahoo.co.jp/okakawa2/62354573.html

 

The fire never actually touches the wood that will be turned into charcoal, and the blue line presumably represents the liquid distillate. The traditional kiln is packed with wood as tightly as possible, but much of the wood is stacked vertically, and there doesn't appear to be an air channel underneath the wood, only a small space that runs just under the ceiling. I might try this next firing.

 

The 55 gallon drum that the design is based around has a limited service life, so perhaps I will make the real version one day. That a fun class that would be!

 

 

So there you have it. Now you can make awesome charcoal too. It's pretty easy and might even be called fun. If the neighbors get fussy, have them come talk to me.

 

 

Now if only I had a forge......

 

Posted with Blogsy