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Warping when making large platter using molds


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#1 Sadie Girl Ceramics

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Posted 02 January 2012 - 09:50 AM

How thick does a slab need to be when making a large serving platter? I am using plaster molds and I dry it slowly. I have had a lot of warping and think that I might need to roll out thicker slabs... I also know that I had over fired a bit when soaking the glaze firing. I can get a handle on the firing but need to know some tips on how to work with these large platters.

#2 trina

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Posted 02 January 2012 - 10:05 AM

How thick does a slab need to be when making a large serving platter? I am using plaster molds and I dry it slowly. I have had a lot of warping and think that I might need to roll out thicker slabs... I also know that I had over fired a bit when soaking the glaze firing. I can get a handle on the firing but need to know some tips on how to work with these large platters.



Hi there, How thick are you cutting your slabs at the moment? I normally use a thickness of about 6-8mm. Clay has a memory so the less you handle it before getting it into the mold the better. Roll it out it every direction and then let it go off a bit (firm up) before placing in the mold. Dry slowly and normally you can see a warp starting even before you fire. Hope that helps Trina

#3 Sadie Girl Ceramics

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Posted 02 January 2012 - 10:14 AM


How thick does a slab need to be when making a large serving platter? I am using plaster molds and I dry it slowly. I have had a lot of warping and think that I might need to roll out thicker slabs... I also know that I had over fired a bit when soaking the glaze firing. I can get a handle on the firing but need to know some tips on how to work with these large platters.



Hi there, How thick are you cutting your slabs at the moment? I normally use a thickness of about 6-8mm. Clay has a memory so the less you handle it before getting it into the mold the better. Roll it out it every direction and then let it go off a bit (firm up) before placing in the mold. Dry slowly and normally you can see a warp starting even before you fire. Hope that helps Trina


Thanks Trina,
When rolling out your slab do you use a slab roller or do you do it by hand? I do not use a slab roller. I generally do use clay that is between 6-8 mm to start with and then pound and roll the clay out until it is about 6 cm thick.. I am flipping the clay each time I roll out the clay. I guess I am wondering if I am handling it too much. I let the platter dry on the mold lightly covers with plastic and some light weights on the platter. Good advise to let it set up for a bit before transferring the clay to the mold.

#4 trina

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Posted 02 January 2012 - 10:42 AM



How thick does a slab need to be when making a large serving platter? I am using plaster molds and I dry it slowly. I have had a lot of warping and think that I might need to roll out thicker slabs... I also know that I had over fired a bit when soaking the glaze firing. I can get a handle on the firing but need to know some tips on how to work with these large platters.



Hi there, How thick are you cutting your slabs at the moment? I normally use a thickness of about 6-8mm. Clay has a memory so the less you handle it before getting it into the mold the better. Roll it out it every direction and then let it go off a bit (firm up) before placing in the mold. Dry slowly and normally you can see a warp starting even before you fire. Hope that helps Trina


Thanks Trina,
When rolling out your slab do you use a slab roller or do you do it by hand? I do not use a slab roller. I generally do use clay that is between 6-8 mm to start with and then pound and roll the clay out until it is about 6 cm thick.. I am flipping the clay each time I roll out the clay. I guess I am wondering if I am handling it too much. I let the platter dry on the mold lightly covers with plastic and some light weights on the platter. Good advise to let it set up for a bit before transferring the clay to the mold.



I normally roll that type of object by hand, just onto a piece of cloth with a couple of slats on each side to give me the thickness. Normally on a plaster bat. Don't flip it over each time, keep everything as flat as you can till you put it into the mold. I think that the flip might be your problem way too much bending going on there.... I also don't use weights, they won't stop it from warping if that is what it wants to do, it only will prevent you from seeing the warp before you put it into the kiln. Trina

#5 Sadie Girl Ceramics

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Posted 02 January 2012 - 10:50 AM




How thick does a slab need to be when making a large serving platter? I am using plaster molds and I dry it slowly. I have had a lot of warping and think that I might need to roll out thicker slabs... I also know that I had over fired a bit when soaking the glaze firing. I can get a handle on the firing but need to know some tips on how to work with these large platters.



Hi there, How thick are you cutting your slabs at the moment? I normally use a thickness of about 6-8mm. Clay has a memory so the less you handle it before getting it into the mold the better. Roll it out it every direction and then let it go off a bit (firm up) before placing in the mold. Dry slowly and normally you can see a warp starting even before you fire. Hope that helps Trina


Thanks Trina,
When rolling out your slab do you use a slab roller or do you do it by hand? I do not use a slab roller. I generally do use clay that is between 6-8 mm to start with and then pound and roll the clay out until it is about 6 cm thick.. I am flipping the clay each time I roll out the clay. I guess I am wondering if I am handling it too much. I let the platter dry on the mold lightly covers with plastic and some light weights on the platter. Good advise to let it set up for a bit before transferring the clay to the mold.



I normally roll that type of object by hand, just onto a piece of cloth with a couple of slats on each side to give me the thickness. Normally on a plaster bat. Don't flip it over each time, keep everything as flat as you can till you put it into the mold. I think that the flip might be your problem way too much bending going on there.... I also don't use weights, they won't stop it from warping if that is what it wants to do, it only will prevent you from seeing the warp before you put it into the kiln. Trina




I often add textures to the surface of the clay before putting it on the mold... I am assuming that you take the clay rolled out on the fabic and turn it over onto the mold. Any suggestion for how to manage the textured side face up on the mold?



#6 Pres

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Posted 02 January 2012 - 12:08 PM





How thick does a slab need to be when making a large serving platter? I am using plaster molds and I dry it slowly. I have had a lot of warping and think that I might need to roll out thicker slabs... I also know that I had over fired a bit when soaking the glaze firing. I can get a handle on the firing but need to know some tips on how to work with these large platters.



Hi there, How thick are you cutting your slabs at the moment? I normally use a thickness of about 6-8mm. Clay has a memory so the less you handle it before getting it into the mold the better. Roll it out it every direction and then let it go off a bit (firm up) before placing in the mold. Dry slowly and normally you can see a warp starting even before you fire. Hope that helps Trina


Thanks Trina,
When rolling out your slab do you use a slab roller or do you do it by hand? I do not use a slab roller. I generally do use clay that is between 6-8 mm to start with and then pound and roll the clay out until it is about 6 cm thick.. I am flipping the clay each time I roll out the clay. I guess I am wondering if I am handling it too much. I let the platter dry on the mold lightly covers with plastic and some light weights on the platter. Good advise to let it set up for a bit before transferring the clay to the mold.



I normally roll that type of object by hand, just onto a piece of cloth with a couple of slats on each side to give me the thickness. Normally on a plaster bat. Don't flip it over each time, keep everything as flat as you can till you put it into the mold. I think that the flip might be your problem way too much bending going on there.... I also don't use weights, they won't stop it from warping if that is what it wants to do, it only will prevent you from seeing the warp before you put it into the kiln. Trina




I often add textures to the surface of the clay before putting it on the mold... I am assuming that you take the clay rolled out on the fabic and turn it over onto the mold. Any suggestion for how to manage the textured side face up on the mold?



If you don't mind me stepping in here. I usually place the mold if a positive onto the slab put a board over top, with a board under neath the cloth, and flip all at once, then smooth the slab to the form. When rolling out larger slabs, I find it easier to throw the clay at an angle a few times to get it flattened out near to the thickness I want to roll to. When throwing toss in different directions. Then roll out in different directions. It seems to me that 6mm is a little too thin, especially with stamped decoration. I use slab sticks from a lumber company of various widths to roll out my slabs. These allow me to adjust thickness depending on the size of the object being made, the type of surface embellishment being used, and if there is any piercing for decoration or handles.

Simply retired teacher, not dead, living the dream. on and on and. . . . on. . . .                                                                                 http://picworkspottery.blogspot.com/


#7 Mark (Marko) Madrazo

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Posted 02 January 2012 - 12:42 PM






How thick does a slab need to be when making a large serving platter? I am using plaster molds and I dry it slowly. I have had a lot of warping and think that I might need to roll out thicker slabs... I also know that I had over fired a bit when soaking the glaze firing. I can get a handle on the firing but need to know some tips on how to work with these large platters.



Hi there, How thick are you cutting your slabs at the moment? I normally use a thickness of about 6-8mm. Clay has a memory so the less you handle it before getting it into the mold the better. Roll it out it every direction and then let it go off a bit (firm up) before placing in the mold. Dry slowly and normally you can see a warp starting even before you fire. Hope that helps Trina


Thanks Trina,
When rolling out your slab do you use a slab roller or do you do it by hand? I do not use a slab roller. I generally do use clay that is between 6-8 mm to start with and then pound and roll the clay out until it is about 6 cm thick.. I am flipping the clay each time I roll out the clay. I guess I am wondering if I am handling it too much. I let the platter dry on the mold lightly covers with plastic and some light weights on the platter. Good advise to let it set up for a bit before transferring the clay to the mold.



I normally roll that type of object by hand, just onto a piece of cloth with a couple of slats on each side to give me the thickness. Normally on a plaster bat. Don't flip it over each time, keep everything as flat as you can till you put it into the mold. I think that the flip might be your problem way too much bending going on there.... I also don't use weights, they won't stop it from warping if that is what it wants to do, it only will prevent you from seeing the warp before you put it into the kiln. Trina




I often add textures to the surface of the clay before putting it on the mold... I am assuming that you take the clay rolled out on the fabic and turn it over onto the mold. Any suggestion for how to manage the textured side face up on the mold?



If you don't mind me stepping in here. I usually place the mold if a positive onto the slab put a board over top, with a board under neath the cloth, and flip all at once, then smooth the slab to the form. When rolling out larger slabs, I find it easier to throw the clay at an angle a few times to get it flattened out near to the thickness I want to roll to. When throwing toss in different directions. Then roll out in different directions. It seems to me that 6mm is a little too thin, especially with stamped decoration. I use slab sticks from a lumber company of various widths to roll out my slabs. These allow me to adjust thickness depending on the size of the object being made, the type of surface embellishment being used, and if there is any piercing for decoration or handles.



Hi everyone, I have not tried making any platterns wet, so all this info is very helpful. But after reading I have a question for (Pres). You said: "I use slab sticks from a lumber company of various widths to roll out my slabs. These allow me to adjust thickness depending on the size of the object being made, the type of surface embellishment being used, and if there is any piercing for decoration or handles." Is there a thickness I should roll relative to the size of the platter? Posted Image

#8 Pres

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Posted 05 January 2012 - 02:05 PM







How thick does a slab need to be when making a large serving platter? I am using plaster molds and I dry it slowly. I have had a lot of warping and think that I might need to roll out thicker slabs... I also know that I had over fired a bit when soaking the glaze firing. I can get a handle on the firing but need to know some tips on how to work with these large platters.



Hi there, How thick are you cutting your slabs at the moment? I normally use a thickness of about 6-8mm. Clay has a memory so the less you handle it before getting it into the mold the better. Roll it out it every direction and then let it go off a bit (firm up) before placing in the mold. Dry slowly and normally you can see a warp starting even before you fire. Hope that helps Trina


Thanks Trina,
When rolling out your slab do you use a slab roller or do you do it by hand? I do not use a slab roller. I generally do use clay that is between 6-8 mm to start with and then pound and roll the clay out until it is about 6 cm thick.. I am flipping the clay each time I roll out the clay. I guess I am wondering if I am handling it too much. I let the platter dry on the mold lightly covers with plastic and some light weights on the platter. Good advise to let it set up for a bit before transferring the clay to the mold.



I normally roll that type of object by hand, just onto a piece of cloth with a couple of slats on each side to give me the thickness. Normally on a plaster bat. Don't flip it over each time, keep everything as flat as you can till you put it into the mold. I think that the flip might be your problem way too much bending going on there.... I also don't use weights, they won't stop it from warping if that is what it wants to do, it only will prevent you from seeing the warp before you put it into the kiln. Trina




I often add textures to the surface of the clay before putting it on the mold... I am assuming that you take the clay rolled out on the fabic and turn it over onto the mold. Any suggestion for how to manage the textured side face up on the mold?



If you don't mind me stepping in here. I usually place the mold if a positive onto the slab put a board over top, with a board under neath the cloth, and flip all at once, then smooth the slab to the form. When rolling out larger slabs, I find it easier to throw the clay at an angle a few times to get it flattened out near to the thickness I want to roll to. When throwing toss in different directions. Then roll out in different directions. It seems to me that 6mm is a little too thin, especially with stamped decoration. I use slab sticks from a lumber company of various widths to roll out my slabs. These allow me to adjust thickness depending on the size of the object being made, the type of surface embellishment being used, and if there is any piercing for decoration or handles.



Hi everyone, I have not tried making any platterns wet, so all this info is very helpful. But after reading I have a question for (Pres). You said: "I use slab sticks from a lumber company of various widths to roll out my slabs. These allow me to adjust thickness depending on the size of the object being made, the type of surface embellishment being used, and if there is any piercing for decoration or handles." Is there a thickness I should roll relative to the size of the platter? Posted Image


When rolling out larger platter-24" diameter I usually use 1/2 of an inch, where as less than that I use 3/8 inch. Most of the time my decoration process on platters involves slip and stamping-some stamping that embosses the clay, and some that just breaks the slip/engobe.

Simply retired teacher, not dead, living the dream. on and on and. . . . on. . . .                                                                                 http://picworkspottery.blogspot.com/





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