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swalger

Cone 5 Clay Bodies Fired To Cone 6

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Our studio inventory consists of Cone 6 Clay Bodies and Glazes. We use L&L Electric Kilns primarily. Our local suppliers have not kept a reliable stock of Cone 6 inventory and we have started looking into other options. One is Aardvark. They do not seem to supply much Cone 6 Clay and I was wondering to what extent Cone 5 clay will handle Cone 6 firing. To be clear, we would be looking to fire Aardvark, Cone 5 Clay bodies with Cone 6 glazes in our electric kilns until we can either find a reliable source of Cone 6 Clay or migrate our inventory over to Cone 5 Clay and Glazes.

 

Might anyone have working experience in this situation?

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Guest JBaymore

Most of their clay bodies show a rather high Apparent Porosity rate (2% and up) ........ which says they likely will tolerate cone 6 just fine.   SOme are so high as to be questionable for functional table wares at cone 5.

 

But as always........ test, test, test.

 

best,

 

.....................john

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As John says, test. . . often. I have used cone 5-6 bodies quite a while, and as I have an L&L that is fired by site cones with no setter, I have overfired when tired, or have over napped. I can say that I have fired to cone 8 and had bloating, fired to cone 7 and no problem, but don't recommend it. I do have a tendency to fire to a hard cone 6, where cone 6 is touching the shelf, and 7 is nearly 40 degrees. I have found that for my colors, thickness of glaze, and clay bodies that this is my best target.

 

I use Standard Ceramics and over the years have used 112,211, 225, 553, and now 630. All have been great to work with, as have been the folks at SC in PIttsburgh. I don't notice a location for you on your profile, that may help folks when you ask questions like your present one.

 

 

 

best,

Pres

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The only problem I can think of is that the top of the kiln could get to C7  and the work might slump.  I had that happen when I was holding a temp and down firing,  Other than that I think you would be alright and you pots will be truly vitrified.  Denice

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I often down fire, but not as much since I got the thicker lid. I like to hold a bit around ^6.5, then drop 30% for 1/2 hr. Kiln pretty even as I do not turn top all the way up, and witness will be very slightly more than target at mid peep.

 

 

best,

Pres

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I'm having issues with an Aardvark cone 5 clay body right now! Particularly, SBF, a clay body I love to throw but when fired to cone 6... bloat!! I even used Steve's custom bisque firing problem to try to rid the issue (iron - gases) and alas, my glaze fire to cone 6 with a 10 minute soak came out bloated. At cone 5 it fired fine, and they assured me that with little difference between 5 and 6 it would be ok, and I trust them, so I'm over here scratching my head.  At 5 I wasn't in love with my glaze maturation so I'm curious how long I can soak at 5 before bloating occurs...

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11 hours ago, BornonSunsetCeramics said:

I'm having issues with an Aardvark cone 5 clay body right now! Particularly, SBF, a clay body I love to throw but when fired to cone 6... bloat!! I even used Steve's custom bisque firing problem to try to rid the issue (iron - gases) and alas, my glaze fire to cone 6 with a 10 minute soak came out bloated. At cone 5 it fired fine, and they assured me that with little difference between 5 and 6 it would be ok, and I trust them, so I'm over here scratching my head.  At 5 I wasn't in love with my glaze maturation so I'm curious how long I can soak at 5 before bloating occurs...

I would first try getting rid of the soak at cone 6. You're just adding heat work there, getting to 6+.

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Hi Neil! 

I've tried just going to 6 with this clay and it bloated as well. The last firing was a batch that I ran  custom bisque firing on before the glaze fire (as opposed to just running the Skutt "slow" program that comes on the kiln. I've fired it to cone 5 with no issue, I just wasn't thrilled with my glaze. Can you recommend a soak time at cone 5?

 

Thanks!

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If it bloats at 6, I would get a different clay. Many glazes need to go up to 6 to work well, so it will be limiting to be stuck at 5. But if you really want to make it work, I would start with a 10 minute hold and increase by 10 minute increments each firing. It'll take a few firings to figure it out. Put some cones in every time to see where you're actually getting. It could be that it works at 5 3/4, but bloats at 6.

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Guest JBaymore
19 hours ago, BornonSunsetCeramics said:

I'm having issues with an Aardvark cone 5 clay body right now! Particularly, SBF, a clay body I love to throw but when fired to cone 6... bloat!! I even used Steve's custom bisque firing problem to try to rid the issue (iron - gases) and alas, my glaze fire to cone 6 with a 10 minute soak came out bloated. At cone 5 it fired fine, and they assured me that with little difference between 5 and 6 it would be ok, and I trust them, so I'm over here scratching my head.  At 5 I wasn't in love with my glaze maturation so I'm curious how long I can soak at 5 before bloating occurs...

Just as an added thought..... are you using witness cones on the shelves, or trusting the computer program to say you are going to cone 6 with a soak?

If you are trusting the computer........ you may be going with more heatwork than a cone 6 level... and that might be the source of the bloating.

best,

................john

 

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3 minutes ago, JBaymore said:

Just as an added thought..... are you using witness cones on the shelves, or trusting the computer program to say you are going to cone 6 with a soak?

If you are trusting the computer........ you may be going with more heatwork than a cone 6 level... and that might be the source of the bloating.

best,

................john

 

ha ha, I think I was typing at the same time you were, on the other thread about this clay.

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