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laurelneth For every minute you are angry, you lose 60 seconds of happiness. Ralph Waldo Emerson

Posts I've Made

In Topic: using crushed soft brick to fire large tiles on

Posted 30 Sep 2012

Lucille Oka, on 30 September 2012 - 01:24 AM, said:
I am sorry that my reply is not what you wanted to hear. My questions, with your answers were intended to show you how you might not need to put anything under the ware at all. But I am glad that you got the answer you wanted. Finis

Sorry, I didn't understand your connection to my question. I started the round tiles by forming a 1/2" slab. When firm enough I took it to the wheel and cut it to a 12" diameter. When soft leather hard I turned it over and using a 1/4 loop tool, carved out approx. 1/4" circular grooves spaced not quite 1/2 apart until I got to the center. After adding clay and carving I scooped out of the back areas where the added clay was thick. Then, I added holes throughout the backside with a drill bit! Believe me, I did everything I could think of to keep this thing together!!! Unfortunately, I don't have a picture of the back to attach. (I take the pics but my daughter gets them on the computer for me cuz I don't know how). These tiles will be part of a larger community project and from what I understand, they will be attached to the project with wires bent over the raised rim. Laurel <><
In Topic: using crushed soft brick to fire large tiles on

Posted 29 Sep 2012

bciskepottery, on 29 September 2012 - 09:55 PM, said:
A cushion of ground soft brick or grog would help lift your tiles off the shelf. I'd suggest a layer that lifts the tiles a quarter of an inch. I would think consistency in the size of the particles is more important. I've used coarse grog and it has worked.

Thanks. That was what I was hoping to hear! Laurel <><
In Topic: Slab cracking

Posted 7 Sep 2012

laurelneth, on 07 September 2012 - 06:03 PM, said:
Ben, on 03 February 2012 - 11:51 AM, said:
I like the idea of getting the large flat piece up off the shelf in the firing too. It gives the heat a better access to both sides of the slab at once. Might try circular kiln shelf supports on their sides IF you already have some. This would get the piece even further off the shelf. If you realy want to take this idea to its extreme you could try firing them standing on edge with a wall of shelf supports or soft bricks blocking the direct heat from the elements from the edges of the piece closest to the elements. This would allow for more even heating of the piece (see below).

Question: How large is your kiln? In an electric kiln heat radiates form the elements. The available radiated heat close to the elements is going to be incredibly high compared to that at the middle of the slab. This can lead to an huge difference in temperature within the piece from edge to center. This could lead to cracking. To minimize this you need to make sure any ware that gets close to the elements is not large enough to have its other side vary far from the elements. ie: a coffee mug can comfortably be fired within a couple of inches of the elements but a large slip cast pot that only clears the elements by the same amount may not survive the firing. Had this happen to a friend. He made some wonderful, large slip cast pieces. Made one that had a 30 piece mold. He designed the thing to just clear the elements when green and never could get one to survive the firings. After some research he tried firing one in a much larger gas kiln and it survived just fine. They just couldn't survive the stress created by the temperature differential from edge to center.

You may also want to try a different method for making the Slab. I'm afraid that hand rolling may introduce stresses into the slab that other methods may not.
Who, on this forum, makes large slabs and how do you do it?
If it were me, I'd follow the Harry Davis method that he used to make kiln shelves as described in his book "A Potters Alternative". Do you have access to a copy?
In Topic: Slab cracking

Posted 7 Sep 2012

Ben, on 03 February 2012 - 11:51 AM, said:
I like the idea of getting the large flat piece up off the shelf in the firing too. It gives the heat a better access to both sides of the slab at once. Might try circular kiln shelf supports on their sides IF you already have some. This would get the piece even further off the shelf. If you realy want to take this idea to its extreme you could try firing them standing on edge with a wall of shelf supports or soft bricks blocking the direct heat from the elements from the edges of the piece closest to the elements. This would allow for more even heating of the piece (see below).

Question: How large is your kiln? In an electric kiln heat radiates form the elements. The available radiated heat close to the elements is going to be incredibly high compared to that at the middle of the slab. This can lead to an huge difference in temperature within the piece from edge to center. This could lead to cracking. To minimize this you need to make sure any ware that gets close to the elements is not large enough to have its other side vary far from the elements. ie: a coffee mug can comfortably be fired within a couple of inches of the elements but a large slip cast pot that only clears the elements by the same amount may not survive the firing. Had this happen to a friend. He made some wonderful, large slip cast pieces. Made one that had a 30 piece mold. He designed the thing to just clear the elements when green and never could get one to survive the firings. After some research he tried firing one in a much larger gas kiln and it survived just fine. They just couldn't survive the stress created by the temperature differential from edge to center.

You may also want to try a different method for making the Slab. I'm afraid that hand rolling may introduce stresses into the slab that other methods may not.
Who, on this forum, makes large slabs and how do you do it?
If it were me, I'd follow the Harry Davis method that he used to make kiln shelves as described in his book "A Potters Alternative". Do you have access to a copy?

My Information

Member Title:: Member
Age:: 65 years old
Birthday:: March 6, 1948
Gender:
Location:: Punta Gorda, Florida
Interests:: All forms of art/craft, animals (I have a cattle dog, two poodles and two cats) gardening (which I don't do), and making things!