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Biglou13

Burkes Strong Celadon

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I'll bet it's crazing because of all the feldspar.  Feldspar's got a pretty high COE due to the potash and soda.  This is why the original celadons craze.  Reformulate so that you get what's supplied by the feldspar from other sources and cut the soda/potash and sub in another flux.  The whiting could use some adjustment, too--that's the highest COE in the recipe.  Insight is your friend here.  Frits too. :)

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Biglou,

I think Ty has something. 

Although Glenn Nelson's base for ^6 has 64% Custer Feldspar, no silica 18 whiting , 9 ball clay 5 talc. That is it.

Here are some  celedons I used in Reduction and one for ^6 Oxidation

They all have much more silica 

Celedon^6     Reduction

Whiting  18.5

Neph. Syn 25.8

EPKaolin 18.8

Silica 31.1

Gerstley Borate               4.6

Red Iron Oxide      1.5           

 

AACC Celedon Cone 6

Color: light to medium green Tested

Surface texture: glossy

Type of firing: Reduction Glaze type: Ca

 

Ingredients: Percent Batch

Flint                       31.00   1550

Nepheline Syenite 30.00   1500

Gerstley Borate 21.00       1050

EPK Kaolin     10.00          500

Whiting            8.00           400

Totals 100.00 % 5000 gm

 

Also add:

Iron Oxide 1.00 50

 

Comments:

May use up to 3% Iron oxide to intensify color

 

Possible Health Hazards:

Flint: free silica-wear a NIOSH approved dust mask when handling dry material

This is one for Oxidation
Selsor Faux Celedon ^6 Oxidation

Whiting 18.5
Neph Syen 25.8
EPK 18.8
Silica            31.1
Gerstley B     4.6
98.8
Copper carb 0.3
Mason #6600 Black 0.02
Tyler Miller likes this

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There is silica in the Nelson celedon, it's coming from the custer. Silica level is a bit low in the Burke celedon but the expansion is so high you would need to add a lot of silica to fix it and the end result would be a glaze doesn't look like the original. It's the sodium and potassium that are the problems, coe's are high because of them.

 

Burke celedon is a gloss isn't it? Do you have a clear that fits your clay without crazing? I would start by working on finding a clear base that pools then add copper and or stains to get the colour you are after.

 

I've got a lot of good clear recipes, let me know what kind of clay you are putting it on if you want a few to try with different coe's. This is a good thing to do with several clear glazes then run the tests through accelerated crazing tests to know the glaze coe that fits your clay for this and future glaze work. There are other factors that come into play but this gets you in the ballpark.

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Min,

 

There is 64% feldspar in Nelson's and 58 % feldspar ( we don't know what feldspar) in Burkes. I know there is Silica in feldspars. but crazing is from several things, not fitting the clay, COE incapatible with clay body or cooling too fast, over firing, or too thick of an application. I agree he needs to add more silica even though there is a lot of flux as supplied by the feldspar, whiting and zinc.
I supplied the recipes as a none technical way to look at the recipes and make a comparison. burke's is short on silica.

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I recently did a test on strong celedon and got crazing as well. I will try Marcia's to see how that goes.

I was wondering if adding some zircopax, about3 % might help and get a cloudy celedon. I've seen zircopax change copper(1%) from a yellow green to a blue(er) green in several different test.

Just another path to explore

Wyndham

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I recently did a test on strong celedon and got crazing as well. I will try Marcia's to see how that goes.

I was wondering if adding some zircopax, about3 % might help and get a cloudy celedon. I've seen zircopax change copper(1%) from a yellow green to a blue(er) green in several different test.

Just another path to explore

Wyndham

 

Have you tried Leah Lietson's chun? It is similar looking to Burkes even though it's not a celedon, has that translucent pooling quality without being overly glossy. It crazed on the clay I was using at the time but with a slight increase in silica it worked. It has some similarities to Burkes. Alumina is a bit low so it might need a bit of tinkering there to bring it up a bit if used on food surfaces. . Base works well with stains  also.(photo is of Leitson's work) of mig1680_sw107f.jpg

 

My version:

Whiting  14

Zinc  12

Minspar  38

OM4  6

Silica  34.5   (original has 30)

Bentonite  2

Copper carb  0 point 3 up to 2 point 0

 

^6 oxidation

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Biglou,

I think Ty has something. 

Although Glenn Nelson's base for ^6 has 64% Custer Feldspar, no silica 18 whiting , 9 ball clay 5 talc. That is it.

Here are some  celedons I used in Reduction and one for ^6 Oxidation

They all have much more silica 

Celedon^6     Reduction

Whiting  18.5

Neph. Syn 25.8

EPKaolin 18.8

Silica 31.1

Gerstley Borate               4.6

Red Iron Oxide      1.5           

 

 

AACC Celedon Cone 6

Color: light to medium green Tested

Surface texture: glossy

Type of firing: Reduction Glaze type: Ca

 

Ingredients: Percent Batch

Flint                       31.00   1550

Nepheline Syenite 30.00   1500

Gerstley Borate 21.00       1050

EPK Kaolin     10.00          500

Whiting            8.00           400

Totals 100.00 % 5000 gm

 

Also add:

Iron Oxide 1.00 50

 

Comments:

May use up to 3% Iron oxide to intensify color

 

Possible Health Hazards:

Flint: free silica-wear a NIOSH approved dust mask when handling dry material

This is one for Oxidation

Selsor Faux Celedon ^6 Oxidation[/size]Whiting 18.5[/size]Neph Syen 25.8[/size]EPK 18.8[/size]Silica            31.1[/size]Gerstley B     4.6[/size]98.8[/size]Copper carb 0.3[/size]Mason #6600 Black 0.02[/size]

 

Marcia what would these celadons be like if I were to add crimson mason stain? I'm looking for a red transparent "celadon" glaze. Would these glazes work for this?

 

Jed

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Min Marcia,

 

Have you tried this recipe from digital fire?

 

G1216M

Cone 6 Ultraclear for porcelains

Material Amount Units +/- *Stat

Minspar 200 8.60 kg

Frit 3134 23.20 kg

Wollastonite 15.20 kg

EPK 24.80 kg

Talc 4.30 kg

Silica 23.80 kg

99.90

 

Has anyone else had experience with this?

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Min Marcia,

 

Have you tried this recipe from digital fire?

 

G1216M

Cone 6 Ultraclear for porcelains

Material Amount Units +/- *Stat

Minspar 200 8.60 kg

Frit 3134 23.20 kg

Wollastonite 15.20 kg

EPK 24.80 kg

Talc 4.30 kg

Silica 23.80 kg

99.90

 

Has anyone else had experience with this?

I have used 1214 but found it to be too shiny for my needs. There are many good glazes on there.

 

Marcia

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Min Marcia,

 

Have you tried this recipe from digital fire?

 

G1216M

Cone 6 Ultraclear for porcelains

Material Amount Units +/- *Stat

Minspar 200 8.60 kg

Frit 3134 23.20 kg

Wollastonite 15.20 kg

EPK 24.80 kg

Talc 4.30 kg

Silica 23.80 kg

99.90

 

Has anyone else had experience with this?

 

Yes, I have tried that recipe. It is a very nice clear on most surfaces although there is a problem with it. Tony Hanson and I had a long back and forth email discussion about it. We both found it formed rough microcrystaline patches, (his term), especially where it broke on ridges and rims. Tried firing cooler, glazing thicker, no soak, long soaks etc, couldn't solve it. He went on to come up with the MK3330 clear that uses strontium frit Fusion F 524 to address the problem with G1216M, however when I tried it it crazed horribly. I can no longer find it on his site but if you want the recipe let me know. 

 

The clear I'm currently using is a 50:50 blend of G1216M and G1215U, fits my ^6 "porcelain" without crazing and has none of the microcrystaline patches. No milky boron clouding on the white clay I use or over the underglazes, needs to go on fairly thick.

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