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I know this has been asked about before and I've been doing some reading and research, but I'm not finding a good overview...

 

Here are my main questions:

 

Do I need a certain type of clay that is specifcally oven safe?

 

Or can I experiment with a clay and glazes I already use?

 

If I really want to make  oven safe cook ware like casseroles and pie plates, what is the best way to accomplish that?

 

 

Thanks!!!

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Most clay suppliers will be able to recommend which of their clay bodies do well in the oven. In general, stoneware bodies do better. Porcelain does not do well. Ultimately you'll have to run some tests. It is also recommended that you do not preheat the oven when using hand made work in the oven, as it lessens the thermal shock.

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I have had good results with all the stoneware clay bodies I've tried (four). I tend to stick to a stoneware with more grog in it. Since it's more robust all around I feel like it will be more tolerant of baking as well. 

 

I have done a lot of reading and research on baking dishes. Some people have said to leave them extra thick, and others say that it doesn't matter if they're thinner, it's just that the walls and bottom must be about the same thickness and without a sharp angle between the base and walls. I can't remember the reason precisely why this helped it to be stronger and handle thermal shock better. Perhaps that it was more of one surface rather than two surfaces joining sharply together? So even on the ones I've made with straight up-and-down cylindrical sides I make sure that there is a gentle little curve connecting the base to the sides rather than a sharp corner. And that's better for baking with anyway! I trim the exterior to follow the interior. 

 

Either way I have been making slip cast and now wheel thrown pie plates for several years. The first few that I made were given to friends and family to quality test. The reason that I believe the information about it being okay for the pie plate to be on the thinner side as long as the walls are even is that the Duncan pie plate slip mold that I have makes a pretty thin pie plate. I model the ones I throw now off of a similar thickness.

 

I send a use and care slip with every one that I have sold or given away. I basically give instructions similar to the way you would use a glass baking dish. No temperature extremes. Don't plunge a boiling hot baking dish into water or take something from a freezer into a preheated oven. Common (or uncommon) sense. 

 

Again if I'm recalling correctly, there cannot be cracks or pits or bubbles or imperfections in the baking dish, even on the outside, because if there are then they become weak points that lead eventually to cracking. 

 

Last note: I often use my stoneware bowls and plates and other little dishes I've made to heat food in the oven, and they're just lovely. I've been slowly replacing all my metal and glass baking pans with ceramic ones. I usually buy the largest ones just because I don't have the kiln for them but even a very cheap ceramic casserole dish is better than the best metal casserole dish in my experience. :) One of these days, try baking half a batch of brownies in a ceramic pan and half the batch in a metal pan and you'll see. 

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The long and short answer to oven ware is "flame ware" clay bodies. The primary focus is COE (coefficient of expansion). Expansion and contraction of the clay primarily, and finding a glaze that does so equally with the clay. The lower the COE, the less the clay expands and contracts. So do your research over using " flame ware pottery". I seem to recall this topic in a few threads, so use the search bar above to find them.

To get you started:

Tony has a good starting outline.

 

Nerd

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If you want to mix your own clay body, flameware is definitely going to hold up the best. But due to the low COE, most glazes won't work on it very well, so it is limiting. I don't know of any commercially available flameware bodies, probably due to the high liability factor. So if you don't want the limitations of flameware, stick with stoneware. The vast majority of handmade pie plates out there in the world are made from stoneware.

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 I don't know of any commercially available flameware bodies, probably due to the high liability factor. 

 

Toki  (near the bottom of the page)

 

 

Standard 762 Kitchenware clay body.  Cone 9.  http://standardceramic.com/products/moist-clays/high-fire-clays/nggallery/page/2

 

 

Important note in THIS discussion since the term "flameware" came up above....... that Standard Clay Body is NOT "flameware".  It is formulated for making non-direct-flame-contact wares.  FLAMEWARE is for direct flame contact ..... like a frying pan.

 

Because flameware will withstand extremes of thermal differentials across the work... it will work better than ANY "normal" stoneware in oven situations.  But flameware is specifically designed for direct flame use.  Stoneware is NOT.

 

best,

 

...............john

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 I don't know of any commercially available flameware bodies, probably due to the high liability factor. 

 

Toki  (near the bottom of the page)

 

 

I stand corrected! I'm very surprised they make one. Like I said before, lots of liability issues with that stuff. There's a reason we use metal pots and pans on the stove.

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 There's a reason we use metal pots and pans on the stove.

 

 

More than a liability issue (but that is large too). 

 

Thermal conductivity of clay is not anywhere near that of metals.  So you put a flameware frying pan over a gas burner... and the places that are right over the actual flame points are REALLY hot.  And the places away from those spots are MUCH colder.  Anyone who knows how to cook would HATE this stuff.  Very uneven temperatures for actual flame use.

 

Played with this a long time ago as a "novelty".  Cooked with it.  And decided it was a "novelty" idea for sure.  "Wow... look at this.  I can put this clay frying pan on the flame and it does not shatter."   Yeah,.... fine.  How does it COOK stuff?

 

best,

 

...............john

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I've a friend who makes those beer can chicken roasters and sells them to go on a barbecue. (insert head shake here)

 

Just making regular ovenware opens you up to problems. Doesn't matter what you tell the customer or print on a care instruction card, someone will do whatever the heck they want with it and blame the maker. "My grandmother has a casserole she has been using for years and....." I've had customers putting frozen puff pastry encrusted brie in a 450 oven and then complain the pot cracked. My sister in-law put frozen battered fish fillets on one of mine into a hot oven and complained when the pot broke. I don't make ovenware for sale anymore. We use it at home but for selling it I don't find it worth the hassle. I know lots of potters who do make and sell it with no problems but I make enough stuff without selling ovenware that I don't need the potential issues. (why is it that people who do the dumbest things are the most vocal afterwards at blaming others?)

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(why is it that people who do the dumbest things are the most vocal afterwards at blaming others?)

 

Because they don't want to say, "Gee, that was dumb of me. I made a mistake. Better remember this for next time." Too much work that way. -.-

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I make a few designs in my line that are meant for the oven. When people buy them, I advise them to treat it like Pyrex, and also to keep it in the middle of their oven space. I know of two cases where my pottery cracked in the oven, and in both cases they were used too close to the broiler or the bottom element. Maybe I should count my lucky stars. In both cases the customers were very regretful like THEY had done something wrong. They both wanted to pay full price for a replacement. And they were very helpful in showing me the damage and helping me diagnose what happened. Overall I still feel comfortable selling ovenware.

 

I'm using commercial stonewares fired to cone 6. My advice for making ovenware is to make walls that are somewhat thicker than most pots. Thicker than a mug wall for sure. And to keep the walls as even as possible. I think the most important thing to avoid is having one area that is considerably thinner than the rest of the pot. It's hard to know this about your work unless you cut it in half, OR if your experience level makes you confident enough. Careful measuring with a needle tool during trimming works too.

 

I also think ovenware should have a wide flat bottom that can span across the bars of an oven rack. I hate seeing "casseroles" that have a narrow base, or worse, feet. And I always trim a shallow footring into the bottom, rather than having a completely flat bottom. This way, when you take it out of the oven and put it onto a cooler surface, most of the bottom doesn't touch the cooler surface.

 

Here's the bottom of a pie dish that I'm going to fire today, just to show the foot ring:

 

post-1612-0-72751600-1489415328_thumb.jpg

oldlady and Chris Campbell like this

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I made a pot when I was newbie, a pie plate. My wife used it for a long time, but I told her and she knows already to put pies in the oven as it preheats and not from room temp. She has used stoneware to cook for a long time. If I was going to make oven safe work I would buy a stamp that says: "Warning: preheat pot in oven & avoid rapid changes in temperature." 

 

I would stamp that on the bottom of every pot I sold if I was selling wares meant to be used in the oven. I don't however. I am not sure if I ever plan to really. 

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