D. Michael Coffee (shyrabbit) Ceramics in Pagosa Springs, CO


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cooling reduction

Postby bonjiri » Jul 4th, '09, 17:57

shyrabbit wrote:c,

No ITC or soda, the discoloration of the kiln interiors is from the reduction atmosphere from the firings only.

Ya, it's great to have the small kiln...I use it a lot!

The following images are of chawan fired in a gas kiln, reduction cooled with mesquite charcoal and water which was introduced into the kiln at 2350 F. I wadded and tumble stacked these bowls.

Michael

Image
Image
Image
Image


COOL !


m

have u tried different glazes besides these non iron colorant/shino looking glazes ?

some of the most interesting effects i've seen is w/ tenmoku and iron rich glazes in cooling reduction. crytallization on the surface, an amazing amount of depth.

tumble stacking ! COOL !

hey, if u want seashells, they make nice marks instead of wadding marks. the clean shells even contain a minute amount of salt. i can send some, let me know. the ones i have are very similar to the ones used in japan.

cooling reduction. first saw this technique demonstrated by nakazato takashi from karatsu. since his show 3 years ago in ginza (tokyo), i went to his studio in karatsu where he demonstrated the firing using an electric kiln and a small 'rat tail' burner inserted at the bottom to create a 'cooling reduction' atmosphere thru carbon monoxide. then sensei proceeded to stick out his hand, as if he needed payment for this. so i just gave him 'five'. he didn't look amused. hehe !

did you do a body reduction at 1600 or so ? or did you fire in oxidation until cone 10 ? water reduction/ hydrogen reduction is cool ! the more reading i do about the tang dynasty kilns, the more i am intrigued w/ the process.

moreover, i've had some interesting effects w/ copper glazes too. can't wait to do more on this.

cooling reduction is fun ! can't wait to do more ! the water is magical

aloha
c
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Postby shyrabbit » Jul 4th, '09, 18:17

c,

The reduction cooled bowls above have no glaze on them. The first bowl has a Helmer kaolin slip applied to the bisque. All the finish effects are from the masquite and water reduction. These pieces ring as clear as a bell.

I've achieved good crystal growth with a wide range of different glazes by simply firing down in reduction after cone 10 is reached. I reduce the gas pressure and fire down to 1750 F., takes about 3.5 hours and then close the kiln and let it cool normally. This firing method also works well with shinos, producing rich oranges.

Thanks for looking and for adding you informational tidbits,
Michael
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thanks !

Postby bonjiri » Jul 4th, '09, 19:13

m

wow. interesting. looks like soda ash residue though.

later i will post a photograph of a piece that a friend gave me, i am wondering how they got this shino to look like this. its gold and bubbly.

thanks too for sharing

much appreciated.

c



shyrabbit wrote:c,

The reduction cooled bowls above have no glaze on them. The first bowl has a Helmer kaolin slip applied to the bisque. All the finish effects are from the masquite and water reduction. These pieces ring as clear as a bell.

I've achieved good crystal growth with a wide range of different glazes by simply firing down in reduction after cone 10 is reached. I reduce the gas pressure and fire down to 1750 F., takes about 3.5 hours and then close the kiln and let it cool normally. This firing method also works well with shinos, producing rich oranges.

Thanks for looking and for adding you informational tidbits,
Michael
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Re: Some images of the SHY RABBIT Kilns

Postby chicagopotter » Jul 4th, '09, 19:17

shyrabbit wrote:Image


Are those commercially available kilns or did you build them? They look great! Such a clean studio...
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Postby shyrabbit » Jul 4th, '09, 19:40

chicagopotter,

I built both of the kilns. I was lucky to have a sheet metal guy in the building next door. He was a big help with the hoods. Due to our semi-remote location in southwest Colorado, obtaining all the required materials was my biggest hurdle.

I love these kilns...does that sound too weird?

Thanks for the comment on the condition of the studio, our studio and gallery are open to the public so I work hard to make that first impression...maybe only another potters will notice(?)
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Postby bonjiri » Jul 4th, '09, 23:02

shyrabbit wrote:chicagopotter,

I built both of the kilns. I was lucky to have a sheet metal guy in the building next door. He was a big help with the hoods. Due to our semi-remote location in southwest Colorado, obtaining all the required materials was my biggest hurdle.

I love these kilns...does that sound too weird?

Thanks for the comment on the condition of the studio, our studio and gallery are open to the public so I work hard to make that first impression...maybe only another potters will notice(?)


cool michael

i'll be assisting in rebuilding a couple kilns this summer.

love all the kilns i've had personal contact with. blood, sweat and tears ! hehe

know exactly what u mean !

cheers !

c
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kilns

Postby bonjiri » Jul 6th, '09, 16:07

michael

your big kiln fires even from top to bottom ?

how does your updraft fire ?

what is your firing schedule like ? u using propane or natural gas ?

cheers

c
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Postby shyrabbit » Jul 6th, '09, 17:04

Cory,

The large kiln fires very even from top to Bottom, less than a 1/4 of a cone. Most people would call this dead even.

Many potters shy away from updraft kilns believing they fire uneven. If fired correctly the are quite even. Updraft kilns take a lot less space that a downdraft, no need for a stack out the back. I love the updraft design because of its simplicity and its over all minimal footprint.

If you're firing an updraft kiln that's not firing even enough try the following:

1. After loading the kiln, put a final layer of kiln shelfs at the top of the last shelf of pots. This is know as a "guard shelf". This will help to deflect the heat back down into the kiln and also increases the thermal mass of the stacked pots. Doing this may reduce the usable stacking volume of the kiln a little.

2. Try staggering the kiln shelf on the same layer by about and inch or two. This will allow a good vertical heat flow up through the center of the stacked pot. Also, this will reduce the usable stacking volume.

3. Try slowing down the firing and reduce the gas pressure. Also, one should pay close attention to not over reducing. An over reducing kiln will fire very uneven and even stall.

These 3 things in combination will solve most of the issue leading to and uneven firing kiln.

I fire with natural gas....one other thought, check the gas orifices for spider webs and little bits of kiln brick debris.

I can post my schedule if you wish(?)

Michael
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thanks michael !

Postby bonjiri » Jul 6th, '09, 18:37

michael

thanks

i've fired updrafts and found them great too. the tip of putting shelves on the top works great. i've used this technique before. also prevents the kiln 'mana' from dropping onto pieces. hehe. usually around the damper up top.

one strange factor i've noticed w/ downdrafts. since its connected to a chimney/exit flue. windy days causes a faster acceleration of firing. not good if u want an even kiln.

i'm opening the kiln on wednesday PM. will see what i get.

thanks

c
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Postby shyrabbit » Jul 6th, '09, 18:42

c,

Good luck with the kiln opening...like luck have anything to do with it.

I look forward to images!

Michael
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Postby shyrabbit » Jul 6th, '09, 19:11

Come to think of it I've never believed much in luck, but I'm not taking any chances. The kiln gods are the insurance. I have hundreds of them. They are created for ever glaze firing...so far they've worked. Funny, if I forget to make one and I remember hours into the firing, a sense of panic flushes over me. I rush to make three as penance, can't take the chance.

Image
Image
Image
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Postby Seeker » Jul 6th, '09, 20:18

:)
It's been fun following your conversation w/ Cory.
I'd been wondering what all the figures on top of the kilns were - now I know!
Cool.
I keep wondering what 'reduction' is.
I'll have to go to wiki or google.
You guys create such beautiful stuff.
Wow.
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kiln gods

Postby bonjiri » Jul 6th, '09, 21:35

hehe

michael

i knew those were kiln gods on the kiln. i was curious on the different forms. thanks for the closeup.

hehe... i make some too. usually w/ soda firing. with gas i usually offer an alcoholic 'sip' via small cup and/or a kiln god.

i'm not laughing.

does your kiln cool fast ? when do you unload ?

aloha

c
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Kiln gods and penance

Postby Little pig » Jul 7th, '09, 16:39

Kiln gods and penance are wonderful things--ritual and cathartic. It a reassurance to me to see that there are those among us who bring small slivers of these spirits into physical space.
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Postby Moss » Jul 7th, '09, 16:55

Seeker - reduction is where there is little or no oxygen in the kiln during firing. This causes metalic oxides to react differently than if there is oxygen available. In general it gives darker more interesting looks to clay bodies which tend to have a lot of iron.

Some glazes are specifically designed to capture the carbon from CO and CO2 to make flashes of gray or dots in some cases. Shinos among other glazes rely on reduction to work.

Oribe and oilspot glazes and most bright colors are developed in oxidation.

Oxidation is easier to do and the equipment is cheaper and more portable.

Reduction is an art in and of itself controlling the atmosphere in the kiln.

Cory and ShyRabbit are both masters of the technique.
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