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Seasoned Warrior

Wood-Fired Turbo Kiln

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One of the greatest drawbacks for me in the use of a wood-fired kiln is the long time it takes to complete a firing. I basically work by myself and Anagama type kilns I have visited in Japan and elsewhere typically take several days to bring up to ^10 consuming several cords of firewood and take the involvement of a small village to run. I just can't stoke a kiln for several days: for me it's just physically impossible. The other day a friend passed on an article from a kiln building workshop held at Lake Superior Community College in which the instructor built a wood-fired kiln described as a turbo kiln which the instructor learned of from potters in Taiwan. The item that really caught my attention was the statement "...it reached cone 12 in an afternoon, and cooled enough to be opened the next day...", an afternoon??? Now that is a time frame I could live with easily. Does anyone know the basic design of this particular type of kiln? the article in "Ceramic Times" didn't give an adequate description nor show enough photographs for me to be able to come to any conclusions as to the dimensions or the configuration.

 

Regards,

Charles

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Guest JBaymore

Charles,

 

Woodifirng in American seems to have taken on an "if it ain't an anagama, it ain't a wood kiln" tone. There are LOTS of ways to wood fire. Don't let the dominance of the anagama and the long fire crowd put you off to wood firing or convince you it is the only "real" way to woodfire. Long anagama firings are wonderful.... but there are "many ways to skin a cat" (sorry for the phrase, cat lovers wink.gif).

 

Contrary to "popular opinion", designing a wood kiln to fire efficiently and quickly is not a very difficult task at all. It is not rocket science wink.gif . An understanding of basic combustion theory and thermodynamics goes a long way in that regard.

 

A lot of the issue with a wood kiln is what you actually WANT the kiln to do..... when it comes to the core design. WHY are you planning on wood firing? What kinds of effects are you after, if wood is to be more than just a source of renewable heat energy? Are you planning on firing glazed wares or looking more for shizenyu (natural ash deposit glazes)? Are you looking for "crusty stuff" like haikaburi and koge? Do you want it to do multiple things? And so on.

 

One of the wood kilns I built in Japan is at a pottery center where the typical noborigama firings are basically 8 day long affairs. They wanted a smaller kiln (it is not exactly small by most western standards) that would allow them fast turnaround for the same effects they wanted to get in the noboris (using youhen charcoal firing). This one is fired in 3 days.....fast for them wink.gif . They now have it and have fired that kiln well over 200 times since 2006. Here's a picture of it: http://www.kanayamay.../kiln/john.html

 

There are lots of questions to answer when designing any kiln....and those lead to certain design constraints/decisions.

 

We'll discuss a lot of this kind of stuff when I PM you (relative to other thread).

 

best,

 

................john

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Ive been curious of the wood fire kilns. Being that Im starting back up this year after 5 years Im not sure my direction. Ive been pitfiring my bisque ware recently trying to hone in a bit on the technique. I have the freedom to move in any direction and I find in coincidental that I log on tonight to see this thread when the past two days I have been thinking of woodfiring. Understandably so I know its time consuming and looks to be a decent amount of work in a sense. My thoughts mainly when it came to wood firing was the choice of wood. Does it matter? as long as it burns? I can understand chemical saturated wood would not be the best choice. The reason Im curious mainly is because the dump outside of my small town always has a mountains worth of pallet wood. My father and I recycle the wood mainly to make dog houses for extra cash. My brother in-law works for the company that is the main contributor to this pallet pile and at one time we were saving the trip to the dump and saving the company money by just having them drop it off at our house since we were half the distance. We had them stop because we could keep up ahahha and now we are still up to our ears in pallets.

 

Most of it seems to be pine. Almost all of it is raw wood and a small amount looks to be treated. So with my little story told, does the wood matter just as long as its not chemical crap?

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Guest JBaymore

The wood matters in a lot of ways....... but in some ways it does not matter. Once again you get the classic standard answer to any ceamics question ........ "It depends". wink.gif

 

Any wood will burn and release heat energy for you. So from the point of view solely of heat energy........ any wood will give you that. Hard woods have more heat energy value per unit volume (cord) than softwoods. And hardwoods tend to burn a bit more slowly. The flame character produced tends to be softer and longer and more sinuous for most softwoods than that for hardwoods. Most softwoods tend to generate more dense and darker smoke than most hardwoods. Hardwood tends to create more coals in the firebox than softwood does.

 

For most firing uses you will want dry wood. While wet wood can be used for creating certain effects once the kiln is at high temperature (assuming you are wishing to go to something like Orton cone 9-14 range), for bringing the kiln to temp, wet wood uses a lot of the heat energy in just driving out the liquid in the wood. In certain types of kilns, (noborigama in particular) extra water vapor in the effluent from wet wood can cause REAL issues in the later (cooler) chambers as it can condense back out of the gases and then "rain" on the relatively cool pieces. Bad rolleyes.gif !

 

Most importantly......... you are correct, you do NOT want to burn any treated or painted or glued/laminated wood. The chemistry of the coating or the glues is basically adding pretty much unknown compounds into the kiln atmosphere as far as the pieces go... and also adding unknown crap into the kiln effluent. Not a desireable thing for the environment, for the potter standing around stoking and breathing the possible fumes, nor for the possibility of adding stuff into the glazes/surfaces that you don't want to be there. For example, pressure treated wood has both arsenic and copper compounds in it; both are reactive in ceramic chemistry, and the arsenic is pretty darn toxic.

 

Then we get into the chemistry of the possible ash deposits. If you are thinking of wood firing for the effects of settling ash causing changes on the unglazed (yakishime) clay body by building up a natural ash glaze deposit (shizenyu), then the chemical content of the ash can be important to you. Every type of wood draws a different mixture of nutrients from the ground and deposits it into the stucture surrounding the cells. So the chemistry of different species of wood's ash is different. Each species tends to produce a particular quality of natural ash deposit. Even geographically WHERE the species grew can affect this slightly.

 

Also the "richest" chemistry of the minerals in wood is deposited in the layer that is just under the bark area. So wood with bark attached (and this outer layer of wood on the trunk) is the most desireable for gertting really good flashing and shizenyu effects. So pallet wood and cut construction scrap lumber will not have as much of this. It certainly still produces some nice effects....... but most folks find better results with wood that is bark laden. But sometimes you burn what you have........ and the balance decision comes from other factors.

 

It is certainly possible to mix the types of wood you burn too. Many people do this. As far as natural ash deposit glazes go, you could think of it as dipping the pice in one glaze and then dipping it in another glaze. You get sort of a "layering" effect, and the interaction of two distince different types of glass, one over the other. Also for holding a kiln back, hardwood releases energy slower.... so that tactic can be used tto your advantage. Overcoming high heat losses at the top end of high temperature firings can often see softwood's fast energy evolution as a good tactic also.

 

Then there is the "free" aspect. Generally........ free is good wink.gif . Woodfiring is already the MOST expensive way to fire ceramics (because of the labor)....... so no sense adding costs if you don't have to. And also that scrap wood headed to the dump is wood that is just going to be burned in a big pile there at the dump....releasing its carbon dioxide for no good reason. Or rotting on the ground and doing the exact same thing. So you might as well make something beautiful with it. I have used a lot of scrap wood from lumber mills and from woodworking shops for almost 30 years in my noborigama.

 

Hope this is of help............ I could write a book on the complexities of wood and wood firing and wood kilns.

 

best,

 

...............john

 

PS: This info should be useful for Charles too.

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MMB,

 

There is a wood-kiln in my area (at Baltimore Clayworks) which is fired entirely with pallet wood. I think they get it for free (or for very cheap) from a local pallet supplier. They take the ones that have lived out their useful lives as pallets.

 

The one thing pallets don't have is bark. I agree with John that bark is the source of many exciting wood-fire outcomes, so Baltimore Clayworks adds mulch from the hardware store.

 

I was once chatting with a customer at an art festival who said he was an expert in "solid fuel appliances" meaning wood stoves and wood-burning furnaces. He said it is wrong to burn pallet wood in these appliances because it burns much faster and hotter than typical cord wood, so hot that it can damage the appliances. He explained that pallet wood has been cut into flat planks, and out in the environment for many years getting very very dry. Compared to cord word which is cut into chunkier pieces and curing for maybe a year. So in other words .... pallet wood + wood-kiln = good idea!

 

Mea

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The wood matters in a lot of ways.......

 

I could write a book on the complexities of wood and wood firing and wood kilns.

 

best,

 

...............john

 

PS: This info should be useful for Charles too.

 

 

Thank you John:

 

Yes it was an interesting discussion and helpful in many ways. You should write the book, it would be helpful to many who are considering a wood-fired kiln. I have a number of books (I'm a book junkie) but not many are aimed at wood-firing specifically. Authors seem to have favorites and so there is a natural bias to the book. Fred Olsen seems to like gas and Ben Parks seems to have bias towards both used and fuel oils.

 

I find some of the terms used a bit obscure to me. I guess being an engineer I like quantifiable terms but I do realize that everything in life can't be quantified and some of the least quantifieable things are also some of the most desireable. You use terms like soft firing and sinuous in realtion to flames and unfortunately these leave me wondering as to how one might classify flame types. I can actually see how one might consider some fires hard and some soft. I know some fires burh fast and hot and some just kind of burn in a pleasant manner with many colors and different flames. Sinuous, I am having more trouble conceptualizing. I am sure a book on the subject would help greatly.

 

Regards,

Charles

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Well John I do appreciate the time you spent typing that all out. Not sure how soon I would get into woodfiring considering Im reteaching myself the basics all over again. Being that I might be moving in a couple of months will give me some time to think about my direction. Also to Id hate to drop cash on building a kiln then have to leave it :( I know the wood source is always there.

 

Visually wood fire kilns look to be permanent structures. Anyone ever had to relocate one?

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In reference to using pallet wood for firing a kiln, I just watched David Hendley's video series, Extrude It, and was looking at his website. He states that his kiln is fired using pallet wood.....here is an excerpt from his website...... The kiln at Old Farmhouse Pottery is heated entirely by burning wood. It is fired once or twice a month, when enough pottery has been made and dried to fill the kiln. A firing takes about 10 hours to reach 2400°F, and two and a half days to cool enough to remove the finished pottery. The kiln has two fireboxes, which must be stoked once every minute or so to keep the temperature rising. Fuel for the kiln comes in the form of scrap from a local pallet factory. The boards are already cut to size, but must be carefully stacked so they can dry for several months before use. http://www.farmpots.com/studio.htm

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Charles,

 

Woodifirng in American seems to have taken on an "if it ain't an anagama, it ain't a wood kiln" tone. There are LOTS of ways to wood fire. Don't let the dominance of the anagama and the long fire crowd put you off to wood firing or convince you it is the only "real" way to woodfire. Long anagama firings are wonderful.... but there are "many ways to skin a cat" (sorry for the phrase, cat lovers wink.gif).

 

best,

 

................john

 

Rather than start a new thread, I thought I'd dove-tail on this one.

 

Along with a couple other MFA students, I've recently been tasked (willingly) with evaluating the feasibility of building a wood-fired kiln for our program. It's an integrated art-design program... none of the faculty on staff currently have ceramics as a primary focus (although several work in clay as part of their oeuvre).

 

So- we'd like to research and build something within the following constraints...

 

1) Feasible for a group with some entry-level knowledge of kiln materials and construction (we've all participated in re-wiring and replacing components on gas-fired and electric kilns)... but no background in building wood-fired kilns.

 

2) Ideally- something that can be fired in a manner conducive to regular participation by undergrads... so maybe not a multi-day anagama-style design.

 

3) Ideally- something that wouldn't totally break the bank. (Although the program has funds for this, and we're willing to fund-raise externally).

 

Anyhow, I was curious as to whether anyone had built or fired with the Manabigama design that bciskpottery cites above? The extensive, repeated validation of this design, along with complete schematics available for purchase, is pretty appealing... as is the short firing cycle.

 

Do people have alternative suggestions?

 

(We'll be researching this over the next year- probably looking to initiate construction in 2016).

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In grad school I mostly fired a cross draft wood kiln. It took 12-14 hours, burned 3 pickup loads of wood, and every pot came out snotty with ash. Wonderful kiln and easy to fire. I used 2 loads of  scrap lumber and 1 load of bark cuts from a local sawmill. The total cost of each firing was about $35 in wood. The key to that kiln was that the fire box was the same size as the ware stack. It was just a catenary arch with a bag wall in the middle and an ash pit under the firebox side. I've also seen it done with a barrel arch, which give you a little more stacking space. Either way it's an easy kiln to build and fire, and can be scaled to just about any size.

 

A single chamber cross draft wood kiln essentially fires just like a gas kiln. You have fuel, air, and a damper. The three work in conjunction to control the atmosphere and rate of climb. The only difference is that your fuel is not putting out constant energy like gas burners, but rather rising and falling with each stoke. But that's easy enough to deal with. If you understand how to fire a gas kiln, you can fire this type of wood kiln. It will take practice, of course, to get the results you want, but just getting it to temperature is not an issue. You can adjust the atmosphere, the pressure in the kiln, the temperature top to bottom, etc, just like a gas kiln.

 

A long time ago, the first wood firing I ever did was at John Balistreri's anagama (6' tall x 30' long) in Denver. It was an 8 day firing. He said he could actually get the whole thing to temperature in less than 24 hours, but there wouldn't be enough ash for anything to look good. So most of the firing was spent just burning wood to build up ash, and for the flame to work its magic.

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On 1/20/2011 at 5:32 PM, bciskepottery said:

John Theis and Bill VanGilder build a manabigama wood fire kiln. Fires in one day to cone 12 using half cord of wood. Here is link: http://www.monocacypottery.com/default.htm

 

If you read the description of the kiln, it says that only the front portion of the kiln gives heavy ash effects. The back half is used for glazed ware. This is why most tube kilns fire for a long time- it takes a lot of back stoking to build up ash. Just getting to temperature is easy. It takes time to get ash effects. Even train kilns, which are quite efficient by comparison, require 2-3 day firings for the back half to get ash effects.

Edited by neilestrick

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A friend of mine has a fast fire down draft wood kiln that has 2 fireboxes, one on each side and the kiln itself is 4 inches of fiber. Fires in about 10 hrs and is about 60 cu ft stacking space. He uses scrap wood from several different sources.

The kiln looks like a sprung arch style, all fiber no brick for the shell.

Wyndham

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A friend of mine has a fast fire down draft wood kiln that has 2 fireboxes, one on each side and the kiln itself is 4 inches of fiber. Fires in about 10 hrs and is about 60 cu ft stacking space. He uses scrap wood from several different sources.

The kiln looks like a sprung arch style, all fiber no brick for the shell.

Wyndham

 

I assume he's not getting a lot of ash effects? Fiber does not typically hold up well to wood ash and vapor.

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John Theis and Bill VanGilder build a manabigama wood fire kiln. Fires in one day to cone 12 using half cord of wood. Here is link: http://www.monocacypottery.com/default.htm

 

If you read the description of the kiln, it ways that only the front portion of the kiln gives heavy ash effects. The back half is used for glazed ware. This is why most tube kilns fire for a long time- it takes a lot of back stoking to build up ash. Just getting to temperature is easy. It takes time to get ash effects. Even train kilns, which are quite efficient by comparison, require 2-3 day firings for the back half to get ash effects.

 

 

This might not be a bad thing, in point of fact... some people might be interested in using the kiln for hi-fire reduction alone.

 

The cross draft kiln you describe sounds like on option we should look into, however.

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Guest JBaymore

 

Charles,

 

Woodifirng in American seems to have taken on an "if it ain't an anagama, it ain't a wood kiln" tone. There are LOTS of ways to wood fire. Don't let the dominance of the anagama and the long fire crowd put you off to wood firing or convince you it is the only "real" way to woodfire. Long anagama firings are wonderful.... but there are "many ways to skin a cat" (sorry for the phrase, cat lovers wink.gif).

 

best,

 

................john

 

Rather than start a new thread, I thought I'd dove-tail on this one.

 

Along with a couple other MFA students, I've recently been tasked (willingly) with evaluating the feasibility of building a wood-fired kiln for our program. It's an integrated art-design program... none of the faculty on staff currently have ceramics as a primary focus (although several work in clay as part of their oeuvre).

 

So- we'd like to research and build something within the following constraints...

 

1) Feasible for a group with some entry-level knowledge of kiln materials and construction (we've all participated in re-wiring and replacing components on gas-fired and electric kilns)... but no background in building wood-fired kilns.

 

2) Ideally- something that can be fired in a manner conducive to regular participation by undergrads... so maybe not a multi-day anagama-style design.

 

3) Ideally- something that wouldn't totally break the bank. (Although the program has funds for this, and we're willing to fund-raise externally).

 

Anyhow, I was curious as to whether anyone had built or fired with the Manabigama design that bciskpottery cites above? The extensive, repeated validation of this design, along with complete schematics available for purchase, is pretty appealing... as is the short firing cycle.

 

Do people have alternative suggestions?

 

(We'll be researching this over the next year- probably looking to initiate construction in 2016).

 

 

Personally I am not a big fan of the Manabigama design. It is a "pre-packaged" deal, which leads to its prevelance... but I know potters that have soon modified it.

 

Identify what the FIRING OUTCOMES you desire are....... that will lead you in the right direction as to kiln design. But you may also find that the firing outcomes and the other constraints you listed are in conflict. In that case, you have to figure the tradeoffs.

 

best,

 

...............john

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Neil,It's not designed for ash effect but a lower cost production kiln with quick firing cycle.

Next time it's fired, I'll try to post a photo.

Another neat thing is the entire front is the door which is lifted off and the interior is accessible.

Wyndham

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Seasoned Warrior,

 

I have the good fortune to be able to fire a wood burning kiln a few times a year. We make cone 10-12 in the span of a day. Like has been wisely mentioned previously in the thread, just because it's not anagama, it doesn't mean it's not legitimate woodfiring. The design of this kiln is called the Phoenix Kiln, named for the Phoenix Workshops of Dunbarton, NH in the late 70s. There's an old issue of the Studio Potter (Vol 7 No 2) that describes it, and it's also discussed in the book Wood-fired Ceramics: Contemporary Practices. It's a small spring arch cross draft that climbs quickly. The placement of the firebox beneath the ware chamber is key. As the flame travels beneath the ware chamber it heats the floor of this section, gaining ambient heat before the flame comes into direct contact with the ware. Also, unlike in an anagama or norigama, there is no struggling with the cool ground. The pots are up off the ground so the pots and chamber heat very evenly.

 

We use rough ends from the lumber mill that we purchase by the bundle and cut down to the right lengths. We use about a three quarters of a cord to a cord and a quarter per firing depending on how long the wood's been drying, how tight the load is, etc. Admittedly there is not the level of ash buildup you'd see in a more traditional 2 or 3 or 4 day firing, so we also salt at cone 10 to supplement. We get great results.

 

The kiln was built in southern Vermont about 10 or 12 years ago, and after being relocated a number of times via crane and flatbed truck, the kiln's owner had the genius/insane idea to put the kiln on a trailer. So for the last few years it has been on a 20' heavy duty trailer. The kiln and trailer weigh about 10 tons total. With about a week's notice (and a large enough truck to haul it) we can take down the flue, support the arch with a form and drive to somewhere new to set it back up to demo or workshop. It's an ordeal to move, but pretty straightforward. The last time we moved the kiln was to it's current home in Burlington, Vermont's south end where the kiln's owner and I run a weekend workshop a couple times a year.

 

As you look to faster woodfiring methods, check out the Phoenix Kiln. It might be a good fit for what you're looking for.

 

C

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In college, we had a Fast Freddy that we fired with used pallets from the technical college next door. If you want any kind of ash deposits, you definitely have to have some kind of bark to this, otherwise the wares look pretty pasty. And we had to stall it out to get said ash to melt, because that sucker went up like stink! You could easily fire that in a day.

Cal

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Thanks guys. Our group is currently engaged in a pretty intense discussion about what we want here... whether it's simply a platform for hi-fire reduction firing (in which case- maybe we should just invest in a gas kiln) or whether we want to experiment with alternate surfaces.

 

These are really helpful suggestions.

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The above link shows a wood fired kiln that was the "Go to" design for earlier generation Seagrove potters. The NC Pottery Center has one almost the same and is fired by different groups 3-6 times a year.

It would be a great kiln if you could lift the lid like a bar-b-Que smoker and not to have to crawl in to load & unload :)

I've long thought if that arch top were several  4 inch fiber blanket sections, it could be the best of both worlds.

Wyndham

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The above link shows a wood fired kiln that was the "Go to" design for earlier generation Seagrove potters. The NC Pottery Center has one almost the same and is fired by different groups 3-6 times a year.

It would be a great kiln if you could lift the lid like a bar-b-Que smoker and not to have to crawl in to load & unload :)

I've long thought if that arch top were several  4 inch fiber blanket sections, it could be the best of both worlds.

Wyndham

If my memory serves me correctly, I think Akira Satake's wood kiln up near Asheville has a top lid. He was telling us about the kiln in a workshop and mentioned that he was too old to crawling through narrow chamber doors, so he build his kiln so the top lifts up and he can get in/out via stepladder.

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I've thought that it would be great to make one so that the entire top half could be lifted with a pulley system. similar to a huge raku kiln.

I'm pretty sure that was Satake's approach; he said he lifted the lid with pulleys, loaded, then lowered the lid.

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