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So any tips for preventing warping on a cone 4 ( yes I mean 4 not 04 :D ) vitreous slip cast clay? It's a tall tiki form that is a little top heavy so they wants to sag/warp. I'm applying amaco velvet underglaze to the exterior that develops a slight sheen so I don't want to lay them on their side...

Also has anyone tried firing amaco celedons at cone 4? I've been experimenting with some recipes but they are coming out more opaque and milky. Kinda in a crunch!

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7 hours ago, Kiln-iman-smallo said:

So any tips for preventing warping on a cone 4 ( yes I mean 4 not 04 :D ) vitreous slip cast clay? It's a tall tiki form that is a little top heavy so they wants to sag/warp. I'm applying amaco velvet underglaze to the exterior that develops a slight sheen so I don't want to lay them on their side...

Also has anyone tried firing amaco celedons at cone 4? I've been experimenting with some recipes but they are coming out more opaque and milky. Kinda in a crunch!

What's the temp rating of the clay body you're using? You're probably just reaching the max point fo the clay body. Try going a cone lower.

Amaco Celadons are made to fire to cone 5/6, so they're going to be a bit under fired at cone 4. It's worth trying them, though.

Why cone 4? If you want to use commercial products or tried-and-true glaze recipes, you'd be better off using a cone 5 body. Cone 4 just isn't a temp that people usually work it, so you're going to have to adjust any recipes you find.

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I was aiming for a low shrinkage, vitrified clay body, also using a recipe that was limited on materials since the availability of supplies has been limited with COVID closing everything down. It's a true cone 4 at 2086°F. I also did a slow cool, might have been too slow to start. I did a 10 min soak at temp since I only had a few pieces testing and may have been too long? 

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44 minutes ago, Kiln-iman-smallo said:

I did a 10 min soak at temp since I only had a few pieces testing and may have been too long? 

Did you use witness cones to see if a ^5 cone was bending? Firing cooler like Neil mentioned and/or casting the piece a bit thicker could help. 

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5 hours ago, Kiln-iman-smallo said:

I was aiming for a low shrinkage, vitrified clay body, also using a recipe that was limited on materials since the availability of supplies has been limited with COVID closing everything down. It's a true cone 4 at 2086°F. I also did a slow cool, might have been too slow to start. I did a 10 min soak at temp since I only had a few pieces testing and may have been too long? 

A 10 minute soak can get you 1/2 a cone. And if you slow cooled from the peak temp that can get you another 1/2 cone or more.

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5 minutes ago, neilestrick said:

A 10 minute soak can get you 1/2 a cone. And if you slow cooled from the peak temp that can get you another 1/2 cone or more.

Yeah that's what seems to be the issue. I know ware will get soft when it's approaching vitrification and obviously when it's overfired... definitely did not account for the retaining heat factor.

Y'all are confirming what I suspected. Thank you! 

4 hours ago, Min said:

Did you use witness cones to see if a ^5 cone was bending? Firing cooler like Neil mentioned and/or casting the piece a bit thicker could help. 

I did and there was a slight slight change in the ∆5. Just too hot! And I definitely will be making the bases thicker. 

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18 hours ago, Kiln-iman-smallo said:

I did and there was a slight slight change in the ∆5. Just too hot! And I definitely will be making the bases thicker. 

Cones chase each other- a perfect cone 4 will often also have cone 5 starting to move too, so you didn't necessarily over fire.

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