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Reduction firing at cone 6

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I have been firing to cone 6 in an electric kiln for 30+ years. Through a lot of trial and error (a LOT of error!) I have discovered a palette of glazes that give my pots the rich, visually textured look that I want. The studio where I teach has just installed a 40-cu.ft. Bailey gas kiln, which we will begin testing in the very near future. I have never fired reduction at this temperature, and am wondering if anyone has some experience in this area. I'm wondering if clay bodies used in oxidation will be suitable for reduction. Anyone have a favorite clay body or glaze you wouldn't mind sharing with me? Any other tips that might help us to find success in our first few test firings? I realize this is a topic with a wide scope. Anything would help.

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Posted 16 January 2012 - 06:26 AM

 

Here are the results from the ^6 firing workshop in Corpus Cristi. The finished pieces are the Clay studio members work and a few of mine. We compared test tiles. I brought my glaze tests using gerstley borate and Jim Tabor made his using 3134 grit. Not a noticeable difference. The Bailey kiln fired like a dream. Nice kiln. It was the first time I used Advancers and they were wonderful to load. Many thanks to Jim and Don Miller. Don has kept precise kiln logs. We deviated from them but I got to understand their control system through his notes.Many of these glazes are from John Britt's article and from some I shared previously with Don Miller of their Clay Studio.

https://www.facebook...=3&l=ad95eb4c8e

https://www.facebook...=3&l=0a6e943454I have posted glaze recipes on this forum. I will look for the link. I fired ^6 reduction for 20 years, 1980-2000 while I was teaching at Montana State University in Billings from 1975-2000.. We switched to ^6 after moving to a new building in 1980. I designed and built a 60 cu. ft. car kiln and a 36-40 cu ft. sprung arch kiln with good insulation bricks. Once the firings started for the semester, I fired the kilns 2-4 times/week til the end of the semester. The glazes my students used over that period can be seen in Michael Bailey's book Oriental Glazes. They are the only cone 6 glazes in that book. There is a Copper red, Celedon, Ohata Red, Temmoku. For more glazes look up John Britt's article in CM on "How Low Can you Go?" on ^6 reduction appeared in Oct. 2009 or 2010. Some corrections were made in Nov. issue. Diane Pancioli worked on 6^ reduction as well.

Marcia

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Marcia Selsor Cone 6 Reduction Glazes from Montana State University-Billings

 

These came from books, NCECA Handouts, student contributions, etc. or reconfigured from ^10 glazes.

 

We used them from 1980-2000.

 

Semi Matt Black ^6 Reduction

 

Manganese Dioxide. 125 2.5

 

Whiting 587.5 11.75

 

F-4 feldspar (soda) 2725 54.5

 

E.P. Kaolin 325 6.5

 

Silica 1250 25

 

Iron Oxide 500 10

 

5000 100.25

 

Shino ^6 Reduction

 

Gerstley Borate 4.9

 

Soda Ash 2.9

 

Neph. Syenite 54.5

 

Spodumene 22.8

 

Ball Clay 14.9

 

 

Copper Red ^6 Reduction

 

Neph Syn 2766.5 54

 

Gerstley Borate 630.5 12

 

Whiting 535.5 10

 

Silica 1067.50 20

 

Tin Oxide 75 1.5

 

Copper Carbonate 20 0 .3

 

Red Iron Oxide 20 0 .3

 

5115 97 .1

 

 

CLEAR ^6 Reduction

 

Whiting 18.5

 

Neph. Syn 25.8

 

EPKaolin 18.8

 

Silica 31.1

 

Gerstley Borate 4.6

 

 

Celedon^6 Reduction

 

Whiting 18.5

 

Neph. Syn 25.8

 

EPKaolin 18.8

 

Silica 31.1

 

Gerstley Borate 4.6

 

Red Iron Oxide

 

 

SemiMatt ^6 Reduction

 

Magnesium Carbonate 1.3

 

Whiting 13.1

 

Zinc Oxide 1.2

 

Neph. Syenite 66.4

 

Spodumene 5.7

 

Silica 12.3

 

100.0

 

Marci’s Matt ^6 Reduction

 

EPKaolin 1150 23

 

Dolomite 1000 25

 

Neph Syenite 1900 38

 

Silica 900 18

 

Whiting 200 4

 

Gerstley Borate 500 10

 

Variables:

 

Blue 1% Cobalt Carb

 

LightGreen1.5%Nickel Carb + 1.5%RedIron Oxide

 

Gray 2.5% Rutile +1.5% Nickel Carb

 

Warm Blue 1% 1% Cobalt Carb+ 5% Manganse Di

 

Tan 6% Manganese Di. +2.5 Red Iron Ox +1%

 

Rutile OR try using only 5% Rutile as a colorant

 

 

Nelson’s Base ^6 Reduction

 

Custer Feldspar 64 1200

 

Whiting 18 450

 

Ball Clay 9 225

 

Talc 5 125

 

96

 

Black= Red Iron Oxide 8%

 

Chocolate = Red Iron Ox 4% +Chrome Ox. 2%

 

Teal=Cobalt carb 1% +Chrome 1%

 

 

White Liner ^6 Reduction

 

Ger. Borate 20

 

Neph. Syenite 30

 

Kaolin 13.3

 

Whiting 9.4

 

Talc 17.2

 

Silica 10

 

Zircopax 10

 

 

ADD :Pumpkin 5% Red Iron + 3% Rutile

 

Gold 3% Rutile

 

Lt. Blue 0.5% Cobalt Carb

 

 

Ohata Red ^6 Reduction

 

Bone Ash 420 12.9

 

Dolomite 240 7.4

 

Gerstley Borate 120 3.7

 

Lithium Carbonate 120 3.7

 

Custer Feldspar 1560 48.1

 

Kaolin 180 5.6

 

Silica 360 11.2

 

Red Iron Oxide 240 7.4

 

3240 100

 

 

 

 

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I have been firing to cone 6 in an electric kiln for 30+ years. Through a lot of trial and error (a LOT of error!) I have discovered a palette of glazes that give my pots the rich, visually textured look that I want. The studio where I teach has just installed a 40-cu.ft. Bailey gas kiln, which we will begin testing in the very near future. I have never fired reduction at this temperature, and am wondering if anyone has some experience in this area. I'm wondering if clay bodies used in oxidation will be suitable for reduction. Anyone have a favorite clay body or glaze you wouldn't mind sharing with me? Any other tips that might help us to find success in our first few test firings? I realize this is a topic with a wide scope. Anything would help.

 

 

I used cone packs beginning with a thumbprint catch cup for a 1/2 ^ 09, and ^04. I used a half because a whole cone drips too much. The other cones were 5,6,7.

I did a body reduction beginning at ^09 and ending at ^04. You can a check reduction flame by holding a stick in the peep hole and it won't ignite due to lack of oxygen. Then a neutral flame up to ^5 going down. even out the kiln with soft reduction flame til ^6 is at 3 o'clock or further down.

Clear the kiln with a neutral to oxidized flame for 5-10 minutes. Shut it down and close the damper.

 

Use the damper to get pressure out of the bottom peep hole during the firing, combinations between burner setting and the damper are crucial and vary on kilns depending of the draw, altitude, barometric pressure, etc.

 

Marcia Selsor

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White cone 6 bodies should work fine in reduction since they have little to no iron in them. But it takes a lot more iron to get darker colors in oxidation than in reduction. It'll take some testing, but in general brown clay bodies will be much darker in reduction, and some will have way to much iron to remain stable in reduction.

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