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Converting Reduction To Oxidation Glaze Formulas


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#1 Pam S

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Posted 09 July 2013 - 09:34 PM

I have the formula for a lovely cone six, reduction glaze called Mint Julip (pale minty green). Is there a way to convert it for oxidation firing? I mixed a small batch and tried it, but it came out off white/beige and crackled. Formula below. Any suggestions?

Gerstley Borate 3%
Magnesium Carbonate 3
Whiting 22
Fero Frit 3124 9
Nepheline Syenite 23
EPK Kaolin 20
Silica 20
Add: RIO 1

As usual, many thanks!

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#2 Biglou13

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Posted 10 July 2013 - 06:10 AM

So you want your cake and eat it too.....

 

Well i  imagine if this was easy there would be a formula by now.

 

in a nut shell (uber simplified) it is the oxygen poor environment in kiln that drives the reduction colors and effects.  a little understanding of what makes redux look so good may help you.

 

So im going to go out on a limb and say no there isint a simple conversion (a+b=c) to  reformulate redux to ox.

there is no formula or process to convert a redux glaze to ox, that i know of.  i have seen acceptable versions of a few reduction glazes "look" in oxidation but it was not a conversion of redux glaze. and only under very specific conditions. again not a direct conversion of redux glaze

 

i have seen conversions of reduction glazes to lower firing temps,  but thats not the question

 

there are  promising series of glazes that are dedsigned to look like reduction glazes..... but they are pretty much new formulas from the ground up, not same redux glaze reformulated. aka stephen hill glazes (there are others)

 

like the saying there no replacment or displacment.......

 

there is no replacment for reduction............ (yet)

 

there are gurus of glaze that may (will) have a better answer. 

 

but i think researching oxidation recipes for the look you want will result in faster results.


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#3 Marcia Selsor

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Posted 10 July 2013 - 07:03 AM

I would substitute copper for the iron and test to get the right shade.
Iron reacts to reduction differently than oxidation. My best description for
iron in oxidation is baby poo brown/yellow. Sorry to be so vulgar, but that is the best description I can think of.
Iron reds need tin and bone ash to make the right crystal formations.

Keep the base glaze recipe and try starting with 1% copper carb. Adjust with more or less to get the shade you're after.

Marcia

#4 OffCenter

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Posted 10 July 2013 - 08:07 AM

A lot of reduction glazes work in oxidation but a glaze with iron in it is one of the exceptions. That small amount of iron usually produces a celadon. To get a celadon (some would use the term "fake celadon") in oxidation substitute copper carb for the iron just as Marcia said.

 

I do want to quibble with with Biglou's "there are  promising series of glazes that are dedsigned to look like reduction glazes..... but they are pretty much new formulas from the ground up, not same redux glaze reformulated. aka stephen hill glazes (there are others)."

This gives the impression that there is some superiority in reduction glazes that potters firing in oxidation are trying to reproduce. That may be the case with some potters but not most. By using carefully researched firing programs and completely rethinking glaze application for spraying I get glazes far superior to anything I ever got in all my years of firing reduction. Steven Hill isn't trying to reproduce reduction firings, he discovered that reduction firings aren't necessary to get fantastic glazing results.

 

Jim


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#5 Pres

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Posted 10 July 2013 - 09:11 AM

Right on Jim. I think that when ^6 first became of interest due to the availability of nice ^10 electric kilns and highter energy costs potters turned to 6 to supplant/replace their fuel burning kilns. Early efforts were to try and replicate the reduction glazes. Now however, potters have found that by using layers of glazes, using underglazes and inglazing that the variety of effect surpass those available with reduction. Tie this with the increased use of stains, newer richer ^6 clay bodies that have narrower range for vitirfication, and better understanding of ^6 in general gives us a rich palette of color, surface and depth. :)


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#6 Wyndham

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Posted 10 July 2013 - 09:27 AM

As  the others have said about Iron in reduction for a Celedon green but, there might be a place for about   0.1% -0.3 chrome oxide as a colorant. The reason I mention this is a past article on cone 6 greens here on CA. I saw a nice mint green I have been thinging about doing, it might work for you.

The crazing might be handled by adding some wolastinite which is aprox 50%calcium 50%silica and backing off some of the whiting.

 

Try some line blends to see what you come up with.

Wyndham



#7 Benzine

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Posted 10 July 2013 - 09:37 AM

Right on Jim. I think that when ^6 first became of interest due to the availability of nice ^10 electric kilns and highter energy costs potters turned to 6 to supplant/replace their fuel burning kilns. Early efforts were to try and replicate the reduction glazes. Now however, potters have found that by using layers of glazes, using underglazes and inglazing that the variety of effect surpass those available with reduction. Tie this with the increased use of stains, newer richer ^6 clay bodies that have narrower range for vitirfication, and better understanding of ^6 in general gives us a rich palette of color, surface and depth. :)

I've noticed, in supply  magazines, they have quite a few glazes now, that mimic a lot of effects (Reduction, Raku, Wood Firing) in an oxidation kiln.


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#8 Pam S

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Posted 10 July 2013 - 01:47 PM

Thanks for the input. For now I'll make note of the suggestions and try again in the future when I have time to play. In the mean time I'll look for a ^6 ox formula with a similar color.

Marcia, great analogy! LOL!

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#9 Marcia Selsor

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Posted 10 July 2013 - 02:03 PM

I think I posted my faux celedon recipe a while ago.
It may be in my gallery.
here is one from my notes.

Celadon University of the Arts
Flint 21
F-4 Feldspar 35
EPK 10
Barium Carb. 8
Gerstley borate 18
Whiting 18
100
Tin Oxide 5
Dark Rutile 2
Copper Carb 1 **** I use .01% Black Stain and no rutile
Another way is to add Mason stain to a good ^6 clear . . .

#10 Mark C.

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Posted 10 July 2013 - 03:11 PM

 Benzine said

(I've noticed, in supply  magazines, they have quite a few glazes now, that mimic a lot of effects (Reduction, Raku, Wood Firing) in an oxidation kiln.)

 
Well that's odd I thought electric oxidation was its own catagory why would anyone try to make the glazes look like something else?
What ever happened to having a raku -wood -reduction and electic kiln.
Soon you will get the same results with a spray can of paint to mimic glaze on playdo. You may have to bake it in your oven to 450.
The key word here is mimic.
Mark

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#11 neilestrick

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Posted 10 July 2013 - 03:37 PM

 

 Benzine said

(I've noticed, in supply  magazines, they have quite a few glazes now, that mimic a lot of effects (Reduction, Raku, Wood Firing) in an oxidation kiln.)

 
Well that's odd I thought electric oxidation was its own catagory why would anyone try to make the glazes look like something else?
What ever happened to having a raku -wood -reduction and electic kiln.
Soon you will get the same results with a spray can of paint to mimic glaze on playdo. You may have to bake it in your oven to 450.
The key word here is mimic.
Mark

 

Exactly. I can't stand all these commercial cone 6 'Shino' glazes. I have yet to see one that can even come close to passing for a real Shino. Green Shino? Really?!?


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#12 Mark C.

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Posted 10 July 2013 - 03:53 PM

How about a watermelon shino Neil. I hear Mateel toys is working on it-will come in a nail polish applicator-its the new line of easy strokes sold in the beauty section of all major drug stores. Also a new hot pink shin out in the fall.

Mark


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