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cone 6 reduction copper red

updated wed 2 jul 03

 

Paul Lewing on mon 30 jun 03


on 6/30/03 11:24 AM, Travis Maxwell at tmmaxwel@BELLSOUTH.NET wrote:

> Does anyone know why copper reds seem to work =
> well in highly expansive glazes?

It's because they have so little alumina. Even cone 10 copper reds have
very little, but they can have more than cone 6 ones.
You'll notice that this glaze has no added clay. Doesn't this thing settle
like a rock? If I were you I'd do a series of tests adding clay (probably
kaolin to avoid muddying the color) and see how much you can get in without
affecting the color.
Good luck.
Paul Lewing, Seattle

Travis Maxwell on mon 30 jun 03


I have been firing the following copper red from Marcia Selsor's list:

Web Red (from Clayart) cone 6 REDUCTION
Neph. Syn 55.33
Gertsley Borate 12.61
Whiting 10.71
Silica 21.35
Add
copper carb .39
tin oxide .99


I fire it in an updraft kiln in about 5 hours to cone 6 on laguna cone 5 =
b-mix. For my taste, the color is perfect. Some white flashing (which I =
like), some random black spots(I like these also), but mostly deep red. =
The problem I have with this glaze is it crazes really bad. I know this =
glaze has the properties of a high expansion glaze, but was wondering if =
anyone could recommend some changes that would reduce the amount of =
crazing while at the same time keep it a good copper red base.

I have tried making copper reds with well balanced formulas that do not =
craze, but I can't get the red color at cone 6. I have also noticed =
that many copper reds by other "famous" potters with a color as good as =
this one are also crazed. Does anyone know why copper reds seem to work =
well in highly expansive glazes?

I would be willing to change my clay body to match this glaze. Does =
anyone know of a good claybody for highly expansive glazes? My guess =
though is this one will be out of the possible limits of a cone 6 clay =
body.

Any help would be great.=20

Travis Maxwell

william schran on tue 1 jul 03


Travis wrote: < The problem I have with this glaze is it crazes
really bad. I know this glaze has the properties of a high expansion
glaze, but was wondering if anyone could recommend some changes that
would reduce the amount of crazing while at the same time keep it a
good copper red base.>
The glaze has no clay and more than half of the recipe is Neph. Sy.
Might try subbing a sodium frit, such as Ferro #3110 for the Neph.
Sy. and a boron frit, such as #3134 for the gerstley borate. Of
course you'd need to recalculate the entire formula.
Most all of the copper reds I've used are in the cone 10 variety and
I encountered the same crazing issue.
Bill

Marcia Selsor on tue 1 jul 03


I use the Archie Bray ^6 "porcelain" after I noticed our glazes fit it
better than the porcelains I had been mixing. I can't tell you how it
differs from the Laguna.
I am glad the color turned out for you. Now to make it fit!
Marcia

Travis Maxwell wrote:
> I have been firing the following copper red from Marcia Selsor's list:
>
> Web Red (from Clayart) cone 6 REDUCTION
> Neph. Syn 55.33
> Gertsley Borate 12.61
> Whiting 10.71
> Silica 21.35
> Add
> copper carb .39
> tin oxide .99
>
>
> I fire it in an updraft kiln in about 5 hours to cone 6 on laguna cone 5 b-mix. For my taste, the color is perfect. Some white flashing (which I like), some random black spots(I like these also), but mostly deep red. The problem I have with this glaze is it crazes really bad. I know this glaze has the properties of a high expansion glaze, but was wondering if anyone could recommend some changes that would reduce the amount of crazing while at the same time keep it a good copper red base.
>
> I have tried making copper reds with well balanced formulas that do not craze, but I can't get the red color at cone 6. I have also noticed that many copper reds by other "famous" potters with a color as good as this one are also crazed. Does anyone know why copper reds seem to work well in highly expansive glazes?
>
> I would be willing to change my clay body to match this glaze. Does anyone know of a good claybody for highly expansive glazes? My guess though is this one will be out of the possible limits of a cone 6 clay body.
>
> Any help would be great.
>
> Travis Maxwell
>
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