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Glaze Warping Pots


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#1 armen

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Posted 11 November 2013 - 03:07 PM

I have glazed a few pots with a glaze made of 50/50 ash and ball clay. The clay is warping round bowls into tacos (both stoneware and porcelain, made by me and by someone else). I guess this is a fit issue, right? Is there something I should consider adding to rectify the issue? I should add that I know very little about glaze chemistry. 



#2 neilestrick

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Posted 11 November 2013 - 05:44 PM

Not necessarily the glazes fault. Are you glazing both inside and outside of the bowls? What cone, what clay, what firing profile, etc? We need a lot more info.


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#3 armen

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Posted 11 November 2013 - 08:30 PM

You're right of course. The extent of what I know is: Glazing inside and out and firing to cone 10 in strong reduction in a gas kiln. Stoneware is a medium grogged ironous body with approx 15% shrknkage, and an English porcelain that shrinks 20ish percent. Ash is from a wood fired pizza place. Not certain of the wood

#4 Mark C.

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Posted 11 November 2013 - 10:05 PM

Are these bowls placed on the outside of the load or inside?-are they flame licked or not?

The glaze fit is just one of many issues that may contribute to your tacos-how thin are they taco shell or thicker?

Mark


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#5 armen

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Posted 11 November 2013 - 11:32 PM

To be honest I'm not sure since this was several months ago. I will mention that the bowls were of reasonable thickness- a thickness that would have faired fine I'm certain using other glazes in our community studio (I.e. Not my own studio, I'm not firing the kiln). Also, our studio manager put some on a just half of a cup, and you could see just that part being squeezed when it came out of the kiln

#6 ayjay

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Posted 12 November 2013 - 05:33 PM

I use a 50/50 Pear wood ash and Ball Clay glaze without any problems, it's always been on basic, cheap, buff firing stoneware, fired to 1260°C in a gas kiln. (I allow 10 -11%  for shrinkage with that clay if I ever need to calculate it for a project).

 

 

 

 

 

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