Unglazed Cone 6 Porcelain

[clayshapes]

Can unglazed cone 6 porcelain touch in a cone 6 firing? (Not a bisque firing - a glaze firing, but without glaze).

 

I'm making a pile of things that will be "cold glazed" after they are high fired and I want to stack them when I fire them.

 

 

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[Marcia Selsor]

use a wax with some alumina added. The alumina will wash away like dust. The porcelain could fuse together..you just never know. better to be safe.I use wax with alumina on porcelain lids fired in place. no problems there.

 

Marcia

[clayshapes]

Thanks Marcia -that was my concern. Good Solution. Do you think the same is necessary with cone 6 stoneware? I'm also using a cone 6 black stoneware for these pieces.

[Marcia Selsor]

Probably so. I used some black clay in France and I think it may have a tendency to fuse just because of the high metallic content.

Marcia

[clayshapes]

Thanks again.

[angela_w]

Hi, 

 

Earlier this year I was making unglazed ^6 porcelain beads and fired them all together in an unglazed porcelain bowl. I never encountered any problems with fusing together. Once or twice I had to tap them a little bit with my finger to loosen them up, but they always came out fine. I also just fired some flat ^6 stoneware discs for another potter at my studio (flat circular slabs, fired in a stack of 4 or 5 deep) and they came out fine as well. I had to pull some of them apart, but it was easily done with my fingers, I didn't need to use a mallet or chisel or anything like that. 

 

If your work isn't super paper-thin delicate you'll probably be fine... but of course it's always a good idea to test before firing a whole kiln that way.

[clayshapes]

Thanks - I'll do a test with a few pieces and see what happens! 

[neilestrick]

Hi, 

 

Earlier this year I was making unglazed ^6 porcelain beads and fired them all together in an unglazed porcelain bowl. I never encountered any problems with fusing together. Once or twice I had to tap them a little bit with my finger to loosen them up, but they always came out fine. I also just fired some flat ^6 stoneware discs for another potter at my studio (flat circular slabs, fired in a stack of 4 or 5 deep) and they came out fine as well. I had to pull some of them apart, but it was easily done with my fingers, I didn't need to use a mallet or chisel or anything like that. 

 

If your work isn't super paper-thin delicate you'll probably be fine... but of course it's always a good idea to test before firing a whole kiln that way.

 

It will totally depend on the porcelain. Some glass over more than others. 

[Marcia Selsor]

I have used several ^6 porcelains. Frost will tend to fuse. It is also translucent. maybe it has a higher flux content. As Neil says, it depends on the porcelain.

If it is mature at ^6 then it may tend to stick.

 

On Black ^6 stoneware. I used some last year when I was in France.It slumped. I was actually able to undo warping by controlling the slumping with clay strips. They knocked off easily at ^5 but black on black may fuse.It depends on the clay body.

 

Marcia

[clayshapes]

My cone 6 porcelain isn't translucent - just very white (It's from Tuckers - called Bright White) and my cone 6 black clay is very sturdy - never warps, which is why I love it so much. A gorgeous clay to work with (although impossible to get glaze color on unless it's blue or red - everything else goes clear or horrible mustard!). 

In any case, the biggest takeaway from all this advice is...as usual... test!

But I'm glad to have all these comments. It will inform my testing. I'm always trying to get away without testing, but it's no use!

 

Thanks everyone. My work is almost dry - I will reserve one shelf in my glaze fire tomorrow for testing these ideas..