linda elfert on sat 21 may 05
I have a cone 9-10 white reduction glaze I love. A sugary matt. Can
anyone who understands glazes better that I tell me if I would get that
same surface in a cone 9 oxidation firing? Linda.
Yanigara White
Custer 38.5
Talc 12.5
Whititng 16.3
Silica 26.9
EPK 2.9
Bentonite 2.9
Daniel Semler on sat 21 may 05
Hi Linda,
This is an interesting glaze. Noticeably low in alumina (almost no clay, w/o
the bentonite bet it settles like a brick) and I would not have picked it for a
matte, though its between the magnesian and silica mattes in John Britt's book.
Cool. In short, I can't see anything that would necessarily favour reduction
over oxidation. Having said that more experienced opinions may differ on this.
Best way to find out, is whack it in the kiln and see. And let us know. One of
the great things about glaze questions on the list is the opportunity for
everyone to benefit from one person's experiment.
Thanx
D
Ron Roy on mon 23 may 05
Hi Linda,
I think it will be the much the same but only if you cool the electric the
same amount of time as it takes for the gas kiln to cool.
RR
>I have a cone 9-10 white reduction glaze I love. A sugary matt. Can
>anyone who understands glazes better that I tell me if I would get that
>same surface in a cone 9 oxidation firing? Linda.
>
>Yanigara White
>
>Custer 38.5
>Talc 12.5
>Whititng 16.3
>Silica 26.9
>EPK 2.9
>Bentonite 2.9
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Peter Cunicelli on mon 23 may 05
Hi All,
I'm still new to glaze chemicals. I just got my copy of John Britt's cone
10 glaze book. Once I stopped drooling over the incredible possibilities,
I realized that the majority of the glaze results was for reduction. At
this time, reduction is not an option for me.
Can someone tell me if there's a way, by looking at a glaze recipe, whether
or not a glaze will do well in one or the other? I would definitely do
extensive testing. It would just be nice to look at a glaze and have an
idea of what my results are going to be. I also know this is a result of a
lot of experience.
Thanks!
Peter (www.petercunicelli.com)
Dave Finkelnburg on mon 23 may 05
Peter,
You seem to have a good perspective on this. Isn't it great that John Britt lists the firing cycle in his great book! As you study that you will see certain patterns develop.
IF you could calculate the glaze, so you knew how much iron was in it, that would be your best indicator of whether the glaze would change in oxidation versus reduction. Iron is a flux in reduction, but is basically an inert colorant in oxidation. It does decompose above cone 9 (see Britt's writings on oilspot glazes!).
Also, iron gets reduced in reduction, making translucent celadons green in low concentrations (<1% Fe2O3), making metallic iron on the surface in high concentrations (>8%), and making yellows, reds and browns in between. Good iron reds, by the way, are oxidation glazes! :-) Shinos, on the other hand, are really reduction glazes, in general. It depends, of course, on the iron.
Since iron is a flux as well as colorant in reduction, it changes glaze appearance, partly because it affects body color (because all stonewares have some to a lot of iron in the clay body).
Copper is the other colorant that really varies with color. Copper blues with barium are typically oxidation glazes. Copper red is the result of reduction.
In general, MOST glazes that work in reduction will fire in oxidation, but they just won't look the same. So rather than make up your mind in advance what will happen, try some testing. Good glazing!
Dave Finkelnburg
Peter Cunicelli wrote:
At this time, reduction is not an option for me.
Can someone tell me if there's a way, by looking at a glaze recipe, whether
or not a glaze will do well in one or the other?
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Windancer Studio: Teresa Testa on mon 23 may 05
Peter,
I have tried quite a few glazes meant for reduction in oxidation. In my experience most of the colors were not similar. What I do now is start with a base glaze, (whether it is oxidation or reduction does not matter) and add my coloring and textural ingredients and test, test, test. I also purchased Val Cushings book on glazes. It had many good high fire oxidation recipes. Write me off list for more information about the book.
Teresa Testa
Windancer Studio
www.windancerstudio.com
Ruth Ballou on mon 23 may 05
Peter,
One of the big differences in the look of a glaze in oxidation vs.
reduction will be the effect of reduction on the clay body. High iron
body.... big difference, low iron body/ porcelain, maybe none. Also
consider how opaque the glaze is and how much the underlying body
will show through. Iron and copper give very different colors in
reduction and oxidation and depend on other glaze ingredients for
color response. Cobalt is blue in ox and reduction, but there is
still some variation depending on what else is in the glaze. Chrome
is rarely used in reduction and is green in oxidation. Zinc, barium,
strontium, whiting and magnesium can all have a substantial impact on
color development. So the base of a reduction glaze may look okay in
oxidation, but may need different colorants for a pleasing effect.
Ruth Ballou
Belgium
On May 23, 2005, at 3:29 PM, Peter Cunicelli wrote:
> Hi All,
>
> I'm still new to glaze chemicals. I just got my copy of John
> Britt's cone
> 10 glaze book. Once I stopped drooling over the incredible
> possibilities,
> I realized that the majority of the glaze results was for
> reduction. At
> this time, reduction is not an option for me.
>
> Can someone tell me if there's a way, by looking at a glaze recipe,
> whether
> or not a glaze will do well in one or the other? I would
> definitely do
> extensive testing. It would just be nice to look at a glaze and
> have an
> idea of what my results are going to be. I also know this is a
> result of a
> lot of experience.
>
> Thanks!
>
> Peter (www.petercunicelli.com)
>
> ______________________________________________________________________
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> melpots@pclink.com.
>
>
Peter Cunicelli on tue 24 may 05
Dave, Teresa & Ruth!
Thanks SO much for your help and information. I realize that none of this
is really going to sink in until I've tested it, but this is a good start.
I work pretty much with porcelain. So, I'm not dealing with iron
content. I have worked with a red brick ^6 stoneware that really had
great results in oxidation.
John Britt's book is wonderful! I can't wait to try some of these
glazes... Currently, I'm putting off buying a kiln (just to keep the
money in my pocket for a bit longer). My next event isn't until October.
So, I figure by the end of July, beginning of August I'll have it. Let
the testing begin!
Thanks again.
Peter (www.petercunicelli.com)
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