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Basic Kiln Design


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#1 Round2potter

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Posted 21 December 2012 - 06:32 PM

Hey all,

I am in the midst of getting together my stuff for this weekends firing on the beach. I have been doing some research and i think i have decided to scrap the more traditional pit fire and go with a very very basic up draft or possibly cross draft kiln that is to be partially dug out into the ground (on the beach). I am trying to sketch out some quick, easy designs for a kiln/firebox that i can put up and take down easily and quickly.

Hypothetically, if i was using regular red clay bricks or the normal (2.25x4x8 inches) How might i accomplish the task of building the roof??

I was thinking about stacking rings of brick into an octagon, do a few layers then make a hexagon for a few layers and so and so on until the diameter has closed itself off well enough i can stack a chimney straight up for the draft. This would in a sense be a sort of beehive kiln.

Also, has anybody every tried to carry the chimney out and away from the kiln before going up with it? This would almost definitely it be a down draft type but it can have an huge effect on the draft.

I doubt that an arch top would be feasible do to the time and effort required, I have seen some info on ancient greek and roman Kilns and they typically had a central support and a square roof that sometimes had rounded inside corners.
I have seen a lot of DIY wood fire raku kilns (which are my #1 design inspiration) and they all generally use an old shelf as a roof; i don't have a shelf, so i need to make mine from brick.

Should i get some scrap rebar to reinforce the outside walls/corners?

I think i want to try and limit myself to about 100 brick +/- a few for the sake of travelling to and from the beach with a thousand pounds of dead weight.......

I have never made a kiln before, but really look forward to trying this out with good company and a few (too many) drinks around the bonfire.

Any info would be great!

Thanks,
-Burt
"There is no such thing as cheating in clay; So long as it works"

#2 Marcia Selsor

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Posted 21 December 2012 - 09:00 PM

One thing to consider is to place the fire box facing the prevalent wind direction. Also the horizontal length of a chimney increases the necessary height of the vertical chimney for the draft to work well. There are formulas to figure that out.
A beehive or bottle shaped kiln is usually an updraft. It is aerodynamic as an up draft kiln not a crossdraft kiln which usually works best with an arch .

You could put a section of stove pipe on the top of the tapered shape. You need to lift the floor off the ground for the fire box to work. You should look into some historical anthropology books. A Classic in the field of Ceramics Ecology is "Ceramics and Man" by Fred Matson. You will find lots of information of early pottery. His disciples have published a lot on this topic. I use to belong to the group of Anthropologists who presented "Current Research in Ceramics Ecology" at the Annual American Anthropology Association meetings.

One of the most interesting books I know is Las Rutas de la Alfareria de Espana y Portugal by Emili Sempere. He examines the origins of pottery traditions from various migrating or invading groups on the Iberian Peninsula: Iberian/Greek, Roman, Celtic, Arabic.


It covers just about all early ceramic technology. The kiln scheme below is classified as a Celtic kiln found in NW Spain, made of granite, has built in steps on the outside for stacking, the column inside is stacked rocks of granite, the spokes are high micaceous clay covered with shards for the floor. The top of the kiln is covered with shards and ash is added during the 11 hour firing which helps insulate. The town is Moveros in the Province of Zamora in Spain.
Sorry the image is so bad. I had a hard time converting it. I wrote an article about this village in the Potters Council Newsletter a year or two ago.






Marcia

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#3 Round2potter

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Posted 21 December 2012 - 09:47 PM

Thanks!
I looked and there is a copy of Ceramics and Man at my college library; i am going to pick it up as soon as i get back from the holidays, which is to say after this first kiln building.

I have been utilizing my colleges online databases to research scholarly and peer-reviewed articles so far; but there is not much for diagrams.

There is also a book on kiln making and firing i have been meaning to add to my collection....

I am super excited to try this out!

Ill post some pictures of whatever i get thrown together during my trip.

No matter what happens i am going to have a good time, i bisque fired my pieces today so i wont have ease into the fire like last week.

-Burt
"There is no such thing as cheating in clay; So long as it works"

#4 Marcia Selsor

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Posted 21 December 2012 - 09:50 PM

I just added to jpgs to my initial post. I hope this helps. I spent a year in Spain documenting potters, kilns and the origins of their traditions.

Marcia

#5 Marcia Selsor

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Posted 22 December 2012 - 06:41 AM

Thanks!
I looked and there is a copy of Ceramics and Man at my college library; i am going to pick it up as soon as i get back from the holidays, which is to say after this first kiln building.

I have been utilizing my colleges online databases to research scholarly and peer-reviewed articles so far; but there is not much for diagrams.

There is also a book on kiln making and firing i have been meaning to add to my collection....

I am super excited to try this out!

Ill post some pictures of whatever i get thrown together during my trip.

No matter what happens i am going to have a good time, i bisque fired my pieces today so i wont have ease into the fire like last week.

-Burt

google Dean Arnold. He also wrote about Moveros and was in the Ceramics Ecology group. ANother was Prudence Rice. One anthology published was "A Pot for All Reasons" ed. by Kirkpatrick and Kolb.
Marcia




#6 Marcia Selsor

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Posted 22 December 2012 - 08:19 AM

I am just learning a new app, Graphics converter. Here is a larger image of a granite kiln being fired with brush. This is a low temperature firing beginning at 3 in the afternoon with the woman Alista doing the "poco a poco". At 6 Paco , her son, arrived to begin stoking in earnest. The firing went to 11 pm. The fire box is cleaned of ashes throughout the firing. Shards make up the cover of the ware. The ashes are thrown on top of the shards helping to insulate the chamber.
Paco said he fires at night so he can see the color better and judge the temperature that way. This was in Moveros , Spain 1987.


Marcia

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#7 neilestrick

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Posted 22 December 2012 - 11:26 AM

100 bricks isn't going to get you very far at all. A simple small design is a Push-Me-Pull-You. It's two long, narrow chambers stacked on top of each other, the lower chamber is for stoking, the upper for the pots. The back end of the stoke chamber leads up into the upper ware chamber, which leads into the chimney. Think of a zig zag going up. You can build it one brick wide for small pots, or use half bricks for middle supports for a wider kiln. The whole thing could be buried for insulation.
Neil Estrick
Kiln Repair Tech
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Owner, Neil Estrick Gallery, LLC
www.neilestrickgallery.com

neil@neilestrickgallery.com

#8 Round2potter

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Posted 28 December 2012 - 06:12 AM

well it was a total bust.......

i fired for ten hours, although i took it slow throughout the start for the greenware in the mix with the bisque.

It all smoked wonderfully, but the whole time i was thinking to myself that from the look of the heat my "throwtogether kiln" is probably better suited as a fish smoker.

As of now i am firing it all again in the woodstove and its going really well, i am easily reaching 08-06 by the judge of color.

I'll throw together some pictures of my epic failure, or some might say, great learning experience, in time.

It was a cone-U-lar bottle kiln that started with one firebox and later i added another small box to get more heat.

I have grand ideas for the next go around; this time it includes some fire brick and a length of chimney pipe.

THE REAL QUESTION I HAVE IS:

What other fuels can i use with wood to get MORE HEAT like; dogfood, or rich hulls, or hay or softwood vs hardwood
Or maybe some of this "dirty coal" everybody is raving about these days being so cheap.

Cheers!

-Burt
"There is no such thing as cheating in clay; So long as it works"

#9 JBaymore

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Posted 30 December 2012 - 10:20 AM

The core principle for kiln design is not fuel but what is called "air handling capacity". This concept is the fundamental core of what I teach in my colleger kiln design and operation courses and in workshops. It is basic industrial combustion design.

You can have all the fuel in the world..... but if you do not have air mixed with the fuel (hence having oxygen to combust the hydrocarbons), well......... what you have is FUEL. Not released heat energy. You have a whole pile of potential heat energy doing you no good whatsoever. Throw in even more fuel... and all you get is more fuel sitting in the kiln's fireboxes (and possibly exiting the kiln as unburned combustible gases).

You need to think about inducing a flow of AIR into that kiln structure, and also about how to get the air to mix with the fuel well. Air handling capacity and mixing arer the keys to developing good combustion.

I'd recommend you look at a bunch of books on kilns to get general ideas about size relationships of flues (inlet and outlet) and how naturally induced draft functions, and how grates are used for solid fuels.


best,

.......................john
John Baymore
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Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#10 Marcia Selsor

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Posted 30 December 2012 - 11:39 AM

Good explanation John. I guess my explanation of "draft" and raising the ware off the floor could have gone further to explain letting the air lets the fuel burn hotter...sort of fanning the flame.
Marcia

#11 Round2potter

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Posted 24 January 2013 - 02:20 AM

Pictures of my epic fail of home woodfiring!
"There is no such thing as cheating in clay; So long as it works"

#12 Round2potter

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Posted 24 January 2013 - 02:21 AM

Pictures of my epic fail of home woodfiring!

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"There is no such thing as cheating in clay; So long as it works"

#13 Mark C.

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Posted 24 January 2013 - 03:38 AM

A couple of helpful suggestions-
larger fire box for better combustion with a little longer draw tunnel
No holes in chimney (charcoal lighter can w/holes has got to go)
Get rid of the chimney cap as it slowing down exit gases
Give up the red low fire bricks before they explode-go to lumber store and buy some chimney bricks-they are cheap and are tan colored-they will handle temps better-not as good as real fire bricks but a lot cheaper for this type of thing.
Use these bricks in the firebox and chamber-red bricks on stack up a ways where its cooler.They will not handle kiln temps and will melt at worst and crack apart at best.
Mark
Mark Cortright
www.liscomhillpottery.com




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