Cooking with clay on an electric cooktop

palo · December 25, 2015

Corelle dishes and "Corningware" have the same weakness as I have personally experienced - slivers of glass and a too curious cat - strained my relationship with her that day due to my strenuous exhortations to "scat!"

I'm still not sure if I retrieved all the fragments.

p

azlee · December 25, 2015

On 12/24/2015 at 7:56 PM, boilsover said:

We differ, sorry. Even moderate surface temperature deltas can and do break all clays, as do physical shocks while being under thermal stress, e.g., from dropping from even small distances. Ask any retailer of Emile Henry's stovetop line what their warranty/return rate is. Buyers should know this before they send you their money.

Clay cookware is a little like modern soda-lime "Pyrex". Some people never experience breakage, but a lot of us do, despite taking precautions.

Happy Holidays!

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The handmade Mexican clay pots are made differently than the Emile Henry pots. Rancho is wrong about a lot stuff, but I have great confidence in his comments about the artisanal clay pots that he both sells and collects. He actually knows about this, because it's his business. Also, only newer Pyrex is made with soda lime glass, older Pyrex was made with borosilicate glass and is less prone to shattering than soda lime glass. Obviously, it's wise to use care with all glass and clay cookware and follow manufacturers recommendations for use but it's not helpful to lump all materials together the way that you do. They all have unique properties that dictate how best to use them in the kitchen

boilsover · December 25, 2015

On 12/25/2015 at 9:30 PM, azlee said:

The handmade Mexican clay pots are made differently than the Emile Henry pots.... They all have unique properties that dictate how best to use them in the kitchen

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Great, since you know a lot about clay wares that are suitable for the stovetop (and are not selling them, unlike Rancho) why don't you educatel me about how the Mexican pots are made differently from the Emile Henry--besides the glazing.

Edited December 25, 2015 by boilsover (log)

Maison Rustique · December 26, 2015

On 12/20/2015 at 8:08 PM, Jaymes said:

I now find myself to be the lucky owner of a brand new Mixteca Clay Olla Bean Pot from Rancho Gordo:

http://www.ranchogordo.com/collections/other-food-items/products/110-mixteca-pot

I've cooked in clay ollas before, but always on a gas burner. Now, I'm in an apartment with one of those glass-top ranges. I hate the thing, of course, but not much I can do about it. In previous houses where I've had to put up with electric stoves, I just bought an outdoor gas grill with a burner attached, but that's not workable here. No yard, just a small balcony, no bbq equipment allowed.

So I'm wondering if anyone has experience with any of the several heat diffusers on the market. How would they work with long cooking in clay. This olla is a thing of considerable beauty, obviously hand-rubbed with stones by someone to create the smooth exterior surface, and I don't want to do anything to risk damaging it.

Suggestions?

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I got one for Christmas--so excited!!!

azlee · December 26, 2015

On 12/25/2015 at 9:34 PM, boilsover said:

Great, since you know a lot about clay wares that are suitable for the stovetop (and are not selling them, unlike Rancho) why don't you educatel me about how the Mexican pots are made differently from the Emile Henry--besides the glazing.

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You seem to be very bright, I think you'll find it more satisfying if you research the differences for yourself, rather than relying on my experience. You can go to the Emile Henry factory in person and see how it's it's done or visit Mexico and watch the clay pots being made or watch any of the many videos available that document each process in detail.

haresfur · December 27, 2015

On 12/25/2015 at 9:34 PM, boilsover said:

Great, since you know a lot about clay wares that are suitable for the stovetop (and are not selling them, unlike Rancho) why don't you educatel me about how the Mexican pots are made differently from the Emile Henry--besides the glazing.

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Ok, Ceramics-101. Not complete but this should give you an idea of the differences.

Lets start at the dawn of time. People found that mud containing a lot of clay minerals (not that they knew about clay minerals) was plastic and could be formed into pots. The first pots, at least in some areas were formed by pressing into baskets. When set on a fire the pots became permanently firm and could be used to hold liquids. Other materials like granite sand or mica were sometimes added to the pots for strength.

The early pots were fired to low temperatures and remained porous. But that doesn't mean it is an inferior thing - just different and with different properties. Many modern ceramics are low-fire like earthenware, terracotta, bricks, roof tiles and some cooking pots. Stick your tongue on one and you can feel the saliva being sucked out into the clay body. The ability to absorb moisture changes the way food cooks in these pots. Romertopf pots are used by soaking in water first to saturate the porous clay and then they slowly dry during cooking. If you want to make an earthenware pot more waterproof, then you have to glaze it. It is actually quite difficult to make a good earthenware glaze unless you use lead, which is frowned upon these days.

If you fire clay to a higher temperature chemical changes take place - mainly formation of the mineral mullite. The clay becomes denser and much less porous. The mullite binds the particles together and the clay body is much stronger. The pots made this way are called stoneware.

If you take a very white clay and fire it to very high temperatures, to the point where it just starts to vitrify (becomes glassy), it turns translucent and is a true porcelain.

So, what about thermal shock? Solids expand when heated. So uneven heating can set up stress and cause the material to break. Glazed pots have different material at the surface from the body and this can make the problem worse because of the differences in thermal expansion between the glaze and clay. Low-fire clay has a different problem - if heated too fast, water in the porous clay can turn to steam rapidly enough to crack the pot. These problems can be avoided in ovens by heating and cooling the pots slowly. Same thing for stove tops but there will always be a pretty strong thermal gradient between the bottom and top of the pot. Earthenware actually handles this gradient quite well because there is a bit of flex in the clay structure. You typically won't find a stoneware that can be used on the stove top.

Some modern ceramics get around the differential thermal expansion problem by formulating a clay body with low expansion. This is done by adding a lot of lithium, usually in the form of the mineral spodumene. The glaze has to have an expansion that matches the body. The pots are non-porous. I'm guessing this is how the Emil-Henry pots are made.

So the Mexican pots and the 'flameware' pots have completely different properties and strategies for managing the problems of stovetop use. Either one can be damaged if pushed beyond its limits but both are well suited to the job. But because of the different properties, the cooking results will be different. I think that the ceramic flameware won't make a huge difference from cooking in metal - neither is porous. Earthenware like the Mexican pots will produce some interaction between the moisture in the pot and in the food and will provide reasonable insulation on the upper surface so it may be more like a mixture of stovetop and oven. I don't know - the proof will be in the tasting.

As an aside, a flameware tagine will benefit from the lower thermal conductivity of the ceramic so the liquid condenses on the top and bastes back down, but it won't have the same properties as an earthenware one. On the other hand, I'm more confident about browning meat in the bottom of mine (gently) and it sure is easy to clean.

boilsover · December 27, 2015

On 12/27/2015 at 2:06 AM, haresfur said:

Ok, Ceramics-101. Not complete but this should give you an idea of the differences.

* * *

So the Mexican pots and the 'flameware' pots have completely different properties and strategies for managing the problems of stovetop use. Either one can be damaged if pushed beyond its limits but both are well suited to the job.

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Thank you for the information. I really appreciate it.

I remain unclear about how the Mexican pots, by "strategy" or property, hold up to stovetop use better than Emile Henry's Flame line. The latter do not hold up all that well. I'm back to believing that, unless you must use the stovetop, clay vessels are best used in ovens.

rancho_gordo · December 28, 2015

Thanks, haresfur.

Fascinating stuff.

I find the deeper I dig, the more interesting this is. And within Mexico, the attributes of the clay vary dramatically. Certain regions are known for their comales, others their ollas, etc.

I'm sorry if it doesn't come across online but my interest here is as an enthusiast. There so far is no recipe for making real money in clay pottery that I can see. I love the pots, I cook with them all the time but it seems like I'm coming off as a shill. Sorry about that. I cook in all types of clay, sometimes daily. I would say very clearly, they aren't for everyone.

If you want to dig deeper, there are a few great threads here from when Paula Wolfert's seminal Mediterranean Clay Pot Cooking came out. I also co-host a group on Facebook called Cooking with Clay. I'm just the admin there. Most of the posts are from enthusiastic clay pot users and even some makers. But be warned, they seem to really like this Mixteca bean pot.

weinoo · December 28, 2015

On 12/28/2015 at 12:26 AM, rancho_gordo said:

I'm sorry if it doesn't come across online but my interest here is as an enthusiast. There so far is no recipe for making real money in clay pottery that I can see. I love the pots, I cook with them all the time but it seems like I'm coming off as a shill. Sorry about that. I cook in all types of clay, sometimes daily. I would say very clearly, they aren't for everyone.

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It certainly seems to me that you're coming across as an enthusiastic user of all types of clay pots for cooking. I can't imagine that you're making a great profit on the Mixteca pots; anyway, the people who are hopefully making any money on these pots are the artisans!

Now your beans, on the other hand - talk about shilling !

haresfur · December 28, 2015

There is nothing wrong with being passionate about your work. No one complains if a cook loves the food they are selling.

It does get complicated since the clay does vary - even within the same deposit and is affected by how it is prepared. I have heard that in China, some potters aged clay for one or two generations. The time and temperature of firing has a big effect. And then there is the skill in making the pot that is critical to the strength. I'm out of touch since I haven't been doing pottery for a while but I'll try to answer any questions if I can.

I will say that all this is a good reason to buy from a reputable source who buys from potters with a record for producing quality pots. :wink:

haresfur · December 28, 2015

On 12/27/2015 at 6:04 PM, boilsover said:

Thank you for the information. I really appreciate it.

I remain unclear about how the Mexican pots, by "strategy" or property, hold up to stovetop use better than Emile Henry's Flame line. The latter do not hold up all that well. I'm back to believing that, unless you must use the stovetop, clay vessels are best used in ovens.

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Well then, cooking in clay on the stovetop probably isn't for you. And that's just fine. Do what makes you smile. I am willing to take the small risk (although I don't own an earthenware bean pot, unfortunately). They have been shown to work well with proper care and a mess on the stove is probably the worst that would happen.

boilsover · December 29, 2015

On 12/28/2015 at 10:43 PM, haresfur said:

Well then, cooking in clay on the stovetop probably isn't for you.

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OK.

By the way, has anyone (e.g., Wolfort) done any real testing of the putuative benefits of cooking in clay? I readily understand how a porous clay vessel might soak up moisture (and pot liquor). But it's far less intuitive to me that the resulting prep would be any "moister". And the idea of a cover resulting in "self-basting" or doufeu-like condensation/precipitation just seems...wrong... considering the humidity inside and the thinness of the dripping condensate. I thought the spikes Staub touts were debunked awhile back. No?

I propose that someone who loves these unglazed bean pots do a little 'sperimentin' with an accurate scale.

But they sure are pretty, and I hope their sale supports some indigenous craftspeople.

**Smithy** · December 29, 2015

On 12/29/2015 at 1:39 AM, boilsover said:

By the way, has anyone (e.g., Wolfort) done any real testing of the putuative benefits of cooking in clay? I readily understand how a porous clay vessel might soak up moisture (and pot liquor). But it's far less intuitive to me that the resulting prep would be any "moister".... <snip>

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I have. Please see this post and this later post in the Moroccan Tagine Cooking topic. There's a fair amount of discussion about what happens and why throughout the topic, but the discussion may be more focused on that question (as opposed to recipes) in the region of those two posts.

weinoo · December 29, 2015

On 12/29/2015 at 1:39 AM, boilsover said:

By the way, has anyone (e.g., Wolfort)

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I believe it's W O L F E R T.

Let's be precise here, please.

Edited December 29, 2015 by weinoo (log)

boilsover · December 29, 2015

On 12/29/2015 at 3:23 AM, Smithy said:

I have. Please see this post and this later post in the Moroccan Tagine Cooking topic. There's a fair amount of discussion about what happens and why throughout the topic, but the discussion may be more focused on that question (as opposed to recipes) in the region of those two posts.

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Interesting, thanks Smithy.

Lots of variables at work. It would be useful to know how much water a given type of clay pot can hold within its walls, and how much (if any) passes through transpiration as opposed to evaporation around the cover.

JoNorvelleWalker · January 3, 2016

On 12/21/2015 at 8:21 PM, rancho_gordo said:

I have dozens of clay pots. OK. I have many more than that and it's a problem I can't shake. And I don't want to.

These pots are designed for open flames. They can take the heat and the woman who makes them puts them right in the fire and laughed when I asked her about starting slowly and working up to a stronger flame. She doesn't bother. Her concern was a hot pot on a cold surface. She doesn't even cure them.
Not all clay pots are the same but these are low fired, unglazed pots and they are built to work.

I have heard of glass electric tops breaking but I don't know the specifics of what made that happen.
You can put them on the BBQ and they are very happy. You will get grease stains and a patina and it only makes you love the pot more.

I have a quick video here for cooking with this pot:
https://vimeo.com/148407270

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Steve, while waiting for my pot to arrive I see that in Heirloom Beans you call for soaking overnight and curing in a 250 deg F oven. Is this still your current thinking?

rancho_gordo · January 6, 2016

No. Now, that seems excessive to me. I just broke in a new pot and didn't do anything and it's doing just fine. If you were concerned, may be soaking it for a few hours is okay. I know other pots have you fill them with water and a garlic clove and cook on low heat until all of the water has evaporated. I think just starting with a low heat and working your way up and using it often should be fine.

JoNorvelleWalker · January 6, 2016

Thanks! The pot came and tomorrow is my day off so I will plan to get it broken in. Probably on a heat diffuser though. The problem is, how do you decide which kind of beans? Hmm.

JoNorvelleWalker · January 7, 2016

My decision was pinquitos. I have a recipe of Dianna Kennedy's pot beans cooking now. Nothing could be simpler (except I used olive oil, as I had no pork fat on hand from which to render lard).

The problem is the pot is coming up to temperature very slowly. Even though Kennedy's recipe does not call for boiling, after forty five minutes the beans were only up to 110 deg F. (I stuck the temperature probe of my Agilent in the pot as a precaution.) I raised the stove setting to medium and now after an hour and fifteen minutes (total) the beans are 145 deg F.

The bottom of the pot is of course not perfectly flat, so there is poor contact with the heat diffuser. Am I being too cautious with the heat?

SLB · January 8, 2016

I will say, since this thread I've used my Mixteca pot directly on the flame twice with no diffuser, and while I'm still anxious about the way it's a little wobbly on the grate, I've been astonished at how much faster the beans come to a boil. With the diffuser, I did often have the feeling that the beans took a weirdly long time to cook. I was definitely cautious with the heat, though, probably letting it stay on low for longer than necessary.

Also, for what it's worth -- I did a long-form cure of the pot when I first got it. I appreciate that Rancho has reported that it's not necessary with this pot, and I'm not trying to argue with anyone on the meaning or the science; but for whatever it's worth, that clay on mines was *dry*.

Edited January 8, 2016 by SLB (log)

rancho_gordo · January 8, 2016

On 1/8/2016 at 2:33 AM, SLB said:

I will say, since this thread I've used my Mixteca pot directly on the flame twice with no diffuser, and while I'm still anxious about the way it's a little wobbly on the grate, I've been astonished at how much faster the beans come to a boil. With the diffuser, I did often have the feeling that the beans took a weirdly long time to cook. I was definitely cautious with the heat, though, probably letting it stay on low for longer than necessary.

Also, for what it's worth -- I did a long-form cure of the pot when I first got it. I appreciate that Rancho has reported that it's not necessary with this pot, and I'm not trying to argue with anyone on the meaning or the science; but for whatever it's worth, that clay on mines was *dry*.

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I don't think it would hurt it to cure it at all.

JoNorvelleWalker · January 9, 2016

My pinquitos came out pretty well. The main problem was the salt. The broth is definitely over salted but the beans are barely salted enough. Kennedy calls for salting only at the end of cooking.

Humorously as luck would have it there is a piece in the NY Times today that calls for adding salt to beans in the beginning:

http://www.nytimes.com/2016/01/13/dining/how-to-cook-beans-recipes-tips.html?ref=dining

...contrary to Kennedy.

Anyhow I'm reheating last night's beans (in a saucepan, not in the Mixteca) as we speak and am about to go have dinner. Pinquitos with Zojirushi rice and rather attractive canned tamales. Fresh organic cilantro.

blue_dolphin · January 9, 2016

I say you need some Santa Maria tri-tip with those pinquitos, @JoNorvelleWalker!!

I used to add salt half way through cooking in an attempt to cut the baby in half WRT bean cooking salt dogmas but sometimes missed my window of opportunity and got bland beans so now I just add it at the beginning.

I await my Mixteca bean pot!

rancho_gordo · January 10, 2016

Did you see this video I made awhile ago? (It's tongue in cheek about the Magic part.)

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>

Edited January 10, 2016 by rancho_gordo (log)

rancho_gordo · January 10, 2016

re salting, I salt at the point that the pot starts smelling like beans. You're right that you want to do it as soon as possible so the beans are salted and not just the broth.

If you over salt, you can try adding a potato.

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