Primitive Archer
Main Discussion Area => Primitive Skills => Topic started by: Jodocus on November 20, 2013, 05:21:42 am
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I improved on my kiln after two firings remained reductive and did not quite reach the temperature I needed. The first version had the firebox coming into the burning chamber on the bottom, and the chimney exited it on top:
http://www.primitivearcher.com/smf/index.php/topic,42950.0.html
Now I made a bigger firebox, moved it's opening to the burning chamber higher, and the chimney exit from the burning chamber to the bottom, so the flames essentially move downward in there. Like this, it gets heated more evenly. I slowly fired the kiln until the flame exited the chimney a couple of inches, then let it go down slowly. Four hours up, then I muffled it, let the fire burn down, then I closed it and let it cool.
The tall udu drum and the largest of the satyrs and ocarinas come from this firing. The black satyr and ocarina come from a reductive firing, the mixed ones from an experiment with charcoal inside the burning chamber. The white and red udu is from a spare lump of store bought clay I had and was painted with red earth before firing, the colour burned in nicely and firmly. The trick was to thin it enough and paint several coats. When the paint was too thick, it would peel off on other pieces I'd tried.
I started that pottery thing cause I wanted four tiny pots to put in paint from ground stones I want to paint a bow with. Then I kinda got carried away with it. I still need the pots cause the ones I made cracked when I filled in the paint :'( And I got a couple more udus drying. But as it will freeze soon, so will my clay and I'll be back to making bows.
I better get those paint pots made soon.
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Cool! :o 8) 8)
Looks like you have it down. Those are great! Nice job.
Wayne
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Very nice pieces Jodocus, Handmade treasures of art are special IMO, looking forward to seeing more of this from you.
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Very nice !
Good job !
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8) 8) 8)
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man that is some nice stuff. Surpassed my modest pottery skills. You must have some good clay where you are, I can barely get mine to cooperate! great looking stuff!
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Oh wow! That is some fine craftsmanship!
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Thanks guys! It's way easier than it looks, you can actually put material back on, imagine that ;D Frost hit today, so that was it with pottery until spring. I got stuff for one or two more firings. Firing is nice on a dark, cold day.
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Very nice pieces.Was the kiln made out clay or mud.
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swamp yeti: the kiln is made from just earth, it's loess that has some clay-like properties and can also be burnt to coarse pottery.
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great job Jodocus!
making mud kilns is the best way to learn about mud kilns.
I've made many as a full time hand building potter. and each one I learn a whole lot from. looks like you are having some successes
and that sure helps! if you want me to share any mud and/or adobe kiln pics of mine message me or just let me know.
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Jodocus,
heres a pic from 1980 of a cob (mud) kiln made over a couple days that fired great.
notice it has a mud lid on top for placing and removing pots inside.
to build the lid , mound a low circular covex pile of dirt on the ground ,cover with plastic, apply the cob mix.
I also put in some sheep fence wire imbedded.. because it will likely develop cracks.
Its a downdraft which means the flue opening is about ground level opposite the firebox (or firing chamber)
fire chamber made by using a 5 gal. bucket on its side with wood wedges to be able to drop the "form" when the mud set.
small fire for the first hour, right at the opening
eventually the wood is thrown in and the flame hits a mud brick to divert it around the pots.
if you want your burnished pots to turn black, get the temp up to above red heat, throw in a bunch of cowpies
and seal everything the opening, the chimney, and anywhere you see smoke leaking out.
we are still using a black salad bowl i made in that kiln from 1980.
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in wet weather the stove pipe was removed and it was covered with a tarp.
when you do a first firing DO NOT PUT POTTERY IN IT.
it will be making lots of steam and steam will kill your pots.
before the kiln is even warmed by fire it should be sun baked for atleast a week.
alot of people lose pots in primitive firings because of steam from the ground or from pots
that weren't dry enough..its a terrible sound to hear...exploding pots
you can also entirely cover your pots inside with packed DRY wood ash mixed with DRY chunks of wood for some colorful flashing"
the wood ash protects the pots from the flame.
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Thank you richardzane!
That's a much more solid construction. I plan to build something more permanent next spring. I really like the idea of the mud lid, I am definitely giong to try that.
Must the pots be protected from the flame? I was actually trying to get them right into the flame ;D
I enjoyed the photograph, too. It doesn't look like you get too much wet weather.
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that was out on the Navajo Rez. but yeah it would get pretty muddy at times.
flame can be an enemy, ESPECIALLY the period of time RIGHT before RED heat. (chemical water is still leaving the clay)
ONCE the pots are beginning to glow, flame won't bother them at all.
if you have a hole in the center of your lid you can open it after red heat and toss in splinters of wood or dung
and it won't bother the clay (if it has plenty of crushed sherd temper in the clay)
if you REALLY want to get into this and want to build an adobe kiln, i do have some step by steps of this one.
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Your fire box and the heat entry is key to high temps. You do not need a bigger fire box just a more efficient one. A fire can only be so hot without some modification to the structure of the fire/ box. The problem comes from poor combustion and the accumulation of charcoal. the larger the fire the more oxygen needed. So a larger fire box will require more oxygen, your kinda now back to the same problem. One solution is to more fully combust the fuel you and not make charcoal. One solution is to introduce air to the bottom of the fire so you will need the fire to be held up so that air/oxygen can move around your fuel. If you create channels under the fire (mouse runs/holes) your oxygen will run under the fire combine with the fuel and enter as heat. There are many variations in forms for this type of kiln engineering. In this post you can see how small the fire box is. The kiln in this post will hit cone 6 in three hours it you let it!
http://www.primitivearcher.com/smf/index.php/topic,24584.15.html (http://www.primitivearcher.com/smf/index.php/topic,24584.15.html)
the kiln in this post reached 1950 degrees and was not able to climb any higher because of the fire box construction and volume issues. I still plan on rebuilding it with a better fire box like in the post above but primitive.
http://www.primitivearcher.com/smf/index.php/topic,24584.15.html (http://www.primitivearcher.com/smf/index.php/topic,24584.15.html)
As I found out there was a lot of math involved in constructing a good woodfire kiln. The size of the fire box has to work with the volume of the kiln and the chimney need to be the correct size to match the other two. There are really good books on the market that will help you understand the dynamics of the flow in your kiln. interesting point is that at a high temp the unburnt gases then become fuel in your kiln so it is important to make things harmonize. I know it kinda takes the fun out of it but it will also save you many hours of trial and error. My next clay walled kiln will have more design and math for sure. See at around cone 5-6 you can convert ash to a green glaze on the surface of the pot and that is a cool thing. If that is not your goal then having in a kiln that is controlable is helpful so you can oxidize or reduce your pottery. good control of the flow will help with that.
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This a cool effect of ash from the wood as it melts on the pot. I know this is kinda high temp stuff.
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high temp firing is a different topic for sure.
fly ash(flying wood ash dust) does melt on and make some great surfaces on High temp pottery.
sewer pipe was salt glazed too for years before it was outlawed for creating toxic fumes.
In my own experience with earthen kilns the best intake vent for a fire box (lower temp firing - up to 1800 degrees) is ABOVE the coals.
I've experimented with both and find if air is drawn over the TOP of the coals burns wood cleaner
and prevents any backfiring. If you have a good draw, you should be able to actually sit fairly close to the firing port and not get your knees burnt.
but its always good to experiment and find out what works best for you.
I'm sure some math helps ,but for me its always been about simply doing it and adjusting to make it better.
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high temp firing is a different topic for sure.
fly ash(flying wood ash dust) does melt on and make some great surfaces on High temp pottery.
sewer pipe was salt glazed too for years before it was outlawed for creating toxic fumes.
In my own experience with earthen kilns the best intake vent for a fire box (lower temp firing - up to 1800 degrees) is ABOVE the coals.
I've experimented with both and find if air is drawn over the TOP of the coals burns wood cleaner
and prevents any backfiring. If you have a good draw, you should be able to actually sit fairly close to the firing port and not get your knees burnt.
but its always good to experiment and find out what works best for you.
I'm sure some math helps ,but for me its always been about simply doing it and adjusting to make it better.
totally agree if your not going for high temps keep it simple.
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Wow, great stuff coming up here :)
But I will certainly keep it simple.
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8) I like satyrs. dp