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Suitable clay body for grill


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#1 Daveweldz

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Posted 11 November 2012 - 11:06 PM

Hi
Please bear with me as I am not informed. Both at work and at home my art form is steel. I was asked develop a pellet fired grill (smoker) for a client. Pretty much all the models on the market are sheet metal. After a far bit of research I'm coming to the conclusion the a ceramic type grill would be a superior product. I just dont konw enough about the subject to decide if this is a really viable approuch. I find myself in completely foreign territory. Again please bear with me.

I'm thinking of basically a standard propane BBQ with the body made of some manner of ceramic material. I'm thinking of a slip. My first question is what type of clay, I started looking at high fired and even refractory type clays. Im thinking this is over kill. The operating temp on a grill like this is in the 500F range maybe 800F max. This is well below any cone temperatures I see on clay bodies out there. So is it safe to say pretty much any clay body will suffice from a temperature stand point?


So if that is the case a more important issue will be strength and toughness for shipping and daily use. Any ideas here would be appreciated.

Insulation and light weight would be another attribute, looking at paper clay, is there a practical limit to how much paper material can be added? From what I can see online about 20% by weight is the limit. Is there another material that could be used as a light weight filler?

Any words of wisdom on producing such a peice in a production type setting owuld be greatly appreciated.

#2 Mark C.

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Posted 11 November 2012 - 11:11 PM

This is a question for a ceramic engineer I feel.Thats my best guess after almost 40 years full time with ceramics.
Mark
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www.liscomhillpottery.com

#3 Daveweldz

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Posted 11 November 2012 - 11:23 PM

This is a question for a ceramic engineer I feel.Thats my best guess after almost 40 years full time with ceramics.
Mark


Thanks Mark

The engineer is what I hope to avoid, what do you think?

#4 Mark C.

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Posted 12 November 2012 - 01:02 AM


This is a question for a ceramic engineer I feel.Thats my best guess after almost 40 years full time with ceramics.
Mark


Thanks Mark

The engineer is what I hope to avoid, what do you think?



I think you are asking for a clay body to take flame and uneven heating-The only body I know that will do this is a flame proof body-
There are some formulas around for this-but they are for functional thrown or pressed forms for the oven or stove top. The only ones I have heard about are home made or industrial made for industry.
What you need is extra strong as well for grill top.-hence the C.E.
Thats my best guess.
Mark Cortright
www.liscomhillpottery.com

#5 OffCenter

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Posted 12 November 2012 - 09:05 AM

Here are examples of the clay bodies Mark mentioned: http://www.studiopot...les/art0017.htm The extremely uneven and sudden heating and cooling of a grill top may be too much for even the best of these clay bodies. Only testing will tell. If you follow though on this let us know what happens.

Jim
E pur si muove.

"But it does move," said Galileo under his breath.

#6 Denice

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Posted 12 November 2012 - 09:19 AM

I'm not sure if I have the answer your looking for, but I was recently looking at the Big Green Egg Grill and noticed that it was made out of clay that is used for kiln shelves in electric kilns. I thought the glaze on it might have been a Cone 8-10. You would need a large kiln and expertise with this material to make something like this, it would be a difficult project. Denice

#7 JBaymore

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Posted 12 November 2012 - 10:01 AM

I think a lot of this depends on exactly what the design is and how it will actually be used. More of a description of the process it will be put to would be very helpful for people here to help out.

For example, I make what are called "furo" for the heating of the heavy cast iron kettles ("chagama")used to heat the water for the Japanese Tea Ceremony. Into these ceramic units is placed a layer of carefully sifted and thickly spread wood ash. On top of the bed of ash, in the center of the "mound, a depression holds carefully placed pieces of wood charcoal that are the heat source. There is a cast iron three legged "trivit" that holds the kettle just above the burining charcoal. The clearance between the edges of the burning charcoal and the side walls of the furo is maybe 4" or so. The space between the widest part of the chagama and the top walls of the furo is maybe 2" or so.

So the ceramic gets quite hot during the long time a traditional ceremony takes place. The important factor here is that the heating up is somewhat gradual. At the end of the ceremony the piece gradually cools off also.

Sometimes a small electric heater (hot plate type thing) is used instead of charcoal in locations that burning charcoal will not work well .... due to ventilation issues. Then there is no bed of ash in the furo.

I make furo out of about 3 different clay bodies....... and all stand up to this use just fine. None is a "thermal shock" body or "flameware" body. All are stoneware, fired to maturity.

The big issue with the clay for you is uneven heating and cooling and the potential thermal shock of rapid heating or cooling. If the heating and cooling is slow and gradual and even, then you are correct that the temperatures involved are not an issue.

Remember... they make "chimeneas" out of clay... and they are not heated all that evenly or carefully. So it is certainly possible. In Japan it is a common object for potters to make small ceramic bowl forms that get metal grills on them for making stuff like yakitori (grilled chicken on skewers). (I am experimenting with this myself at the moment.)

Unfortunately you are going to have to test, test, test. With the lack of info on the process itself, I'd be thinking of a refractory clay body (heavy fireclay based) that likely contained a good precentage of fine sawdust to burn out during the firing process and provide some insulating value to the wall section, as well as some "open-ness" to deal with expansion contraction issues...... and not fire it to maturity, but well below that.

Is the ceramic component going to have serious aesthetic involvement in this piece, or will it purely be a functional aspect? That too will help to dictate what you do.

best,


................john
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Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#8 Matt Oz

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Posted 12 November 2012 - 10:39 AM

Maybe you’ve seen them already, but as Denice mentioned there are companies that make ceramic grills, like this one.

http://primogrill.com/

The Egg and Primo are Kamado style

#9 mss

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Posted 12 November 2012 - 01:32 PM

This may be of interest--ceramic fireplace stoves. http://www.ceramicstove.com/wp/

#10 Conniefi

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Posted 12 November 2012 - 06:04 PM

I am working on BBQ. I have met with engineers from refractory companies.
First get yourself powered refractory brick clay
make a slip and pour it into a mold.

Then you will need to have a digital controller on your kiln
fire it raising it to 50 degrees each hour for about 9 to ten hours. (this depends on your kiln)
Then glaze it and refire at cone 6 for your glaze.
Without a digital controller you can not get it to proper refractory temp

#11 Conniefi

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Posted 12 November 2012 - 06:06 PM

I am working on BBQ. I have met with engineers from refractory companies.
First get yourself powered refractory brick clay
make a slip and pour it into a mold.

Then you will need to have a digital controller on your kiln
fire it raising it to 50 degrees each hour for about 9 to ten hours. (this depends on your kiln)
Then glaze it and refire at cone 6 for your glaze.
Without a digital controller you can not get it to proper refractory temp


I am also experimenting with raku clay and refractory clay. This I am told should also work.

#12 Mark C.

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Posted 12 November 2012 - 06:31 PM

I have been around two clay BBQs in my life-both cracked badly over time.
I know they still sell them but that does not mean they hold up.
The refractory clay body sounds like a good way to go.
Mark
Mark Cortright
www.liscomhillpottery.com

#13 neilestrick

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Posted 12 November 2012 - 06:49 PM

I'm thinking something like a mullite kiln shelf formula, but further opened up like John mentioned, with the addition of sawdust, pearlite, etc. It would handle the thermal shock fairly well, but also be hard and durable. Here's a mullite kiln shelf recipe I had on file.

Mullite 50%
Calcined Kaolin 20%
Talc 20%
Fine Grog 10%
Fire to cone 11
Absorption 18%
Shrinkage 2%
Neil Estrick
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neil@neilestrickgallery.com

#14 Daveweldz

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Posted 12 November 2012 - 08:37 PM


I am working on BBQ. I have met with engineers from refractory companies.
First get yourself powered refractory brick clay
make a slip and pour it into a mold.

Then you will need to have a digital controller on your kiln
fire it raising it to 50 degrees each hour for about 9 to ten hours. (this depends on your kiln)
Then glaze it and refire at cone 6 for your glaze.
Without a digital controller you can not get it to proper refractory temp


I am also experimenting with raku clay and refractory clay. This I am told should also work.



#15 Daveweldz

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Posted 12 November 2012 - 08:37 PM


I am working on BBQ. I have met with engineers from refractory companies.
First get yourself powered refractory brick clay
make a slip and pour it into a mold.

Then you will need to have a digital controller on your kiln
fire it raising it to 50 degrees each hour for about 9 to ten hours. (this depends on your kiln)
Then glaze it and refire at cone 6 for your glaze.
Without a digital controller you can not get it to proper refractory temp


I am also experimenting with raku clay and refractory clay. This I am told should also work.



#16 Daveweldz

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Posted 12 November 2012 - 08:52 PM

Thank you every one for the input.


I will attempt to explain this a bit better. This would be a wood pellet grill, were small amounts of wood pellets are feed into a burner pot. Something like a table spoon every minute. The burner pot its self is typicaly a separate part about the size of a coffee cup and can be held off the clay surface. So one advantage is that there would be no burning fuel against the body. Also the burner pot requires combustion air from a blower so the heat is circulated fairly evenly thru out the enclosure.


Yes the Egg type BBQ grill is along the lines I was thinking of, but laid on its side. Think of a propane tank laid on its side and split horizontaly so the top is a lid.


I was hoping the exterior would be appealing.

#17 Daveweldz

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Posted 12 November 2012 - 08:53 PM

Thank you every one for the input.


I will attempt to explain this a bit better. This would be a wood pellet grill, were small amounts of wood pellets are feed into a burner pot. Something like a table spoon every minute. The burner pot its self is typicaly a separate part about the size of a coffee cup and can be held off the clay surface. So one advantage is that there would be no burning fuel against the body. Also the burner pot requires combustion air from a blower so the heat is circulated fairly evenly thru out the enclosure.


Yes the Egg type BBQ grill is along the lines I was thinking of, but laid on its side. Think of a propane tank laid on its side and split horizontaly so the top is a lid.


I was hoping the exterior would be appealing.



#18 Daveweldz

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Posted 12 November 2012 - 08:55 PM

Sorry one more thing, I was not looking to do the grilling surface out of ceramic, just the body of the enclosure.

Thanks again

Dave

#19 Mark C.

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Posted 12 November 2012 - 09:04 PM

I'm thinking something like a mullite kiln shelf formula, but further opened up like John mentioned, with the addition of sawdust, pearlite, etc. It would handle the thermal shock fairly well, but also be hard and durable. Here's a mullite kiln shelf recipe I had on file.

Mullite 50%
Calcined Kaolin 20%
Talc 20%
Fine Grog 10%
Fire to cone 11
Absorption 18%
Shrinkage 2%


I'd suggest adding some kyanite to this ( for long crystal strength) and reducing the talc as well as opening up this body
Mark
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www.liscomhillpottery.com

#20 OffCenter

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Posted 13 November 2012 - 02:51 PM

Sorry one more thing, I was not looking to do the grilling surface out of ceramic, just the body of the enclosure.

Thanks again

Dave


Oh! Well nevermind.
E pur si muove.

"But it does move," said Galileo under his breath.




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