low dome clay oven

[jpmort]

I think I have decided to build a low dome clay oven, primarily for pizzas. Like most people I have spent ages reading through as much as I can find, and this is where I have got to:

I am looking for 36'' internal oven diameter, as I want it to heat up quickly, I am pushed for space, and a pizza at a time is fine with me.

I am going to build it directly on the ground, on a bank of earth. I will flatten the earth and make a solid bed for the oven.

I am not sure if I use clay from the soil, or buy some...

I will use lime mortar for the external render, for waterproofing. NHL 5.

The oven floor, I have some large terracotta tiles I hope to use.

So, if anyone would like to advise on anything I have listed that would be great. My main questions are:

1. I am placing the hearth on soil. What insulation would you recommend, and what sort of a base to keep it all from moving?

2. Can clay heat up enpugh to give 400C degrees?

3. Will clay be strong enough for a low dome?

4. Am I mad?

Many thanks for any responses...

John

[Archena]

Re: low dome clay oven

Okay, so this isn't the most prompt reply ever...


1) I would guess a sand base will do as long as it is thick enough. Definitely need to consider mortar if the tiles are small but as long as the walls contain the shift sand should do for large tiles.

2) <Plugs 400C into temperature converter> 752F? Yep, it should get at least that hot - perhaps hotter depending on design.

3) Low domes are difficult for any material. I would guess you'd need to use straw (adds tensile strength) and whatever you do don't even think about removing the core until it has had at least a few days drying time. I've seen people begin firing as they clear the core but I'm not sure about how that's done.

4) Dude, rather than use the nice oven in your house you want to bake pizza in your backyard in an oven fired by wood - of course you're crazy! Welcome to the club!

[jpmort]

Re: low dome clay oven

Thanks for that reply, and I appreciate it despite the delay!

Due to the weather here and the problem I have had in getting clay, I am postponing the project until next year. In the meantime I will gather up more knowledge. In the meantime I am still making pizzas in my barbecue.

I found your information informative and reassuring... I have decided to try a low dome with clay and I will ensure that the clay is dry before removing the core! Good advice. I am thinking now if I need insulation or not. I am only going to fire it up to make a few pizzas at a time and maybe the insulation is not so critical with me.

Thanks,
John

[dmun]

Re: low dome clay oven

I am thinking now if I need insulation or not. I am only going to fire it up to make a few pizzas at a time and maybe the insulation is not so critical with me.

You MUST insulate! Below and above! There is no greater truth in oven building.You simply won't make "a few pizzas at a time" if you can't get it up to pizza temperature. Even the ancient Romans insulated their ovens with tufa. To do otherwise will be to burn forests of wood, and produce only smoke.

[jpmort]

Re: low dome clay oven

OK, thanks for that... I have now decided I will insulate.

John

[luca]

Re: low dome clay oven

I beg to differ on the insulation question! I built a clay only oven about five years ago simply out of our native clay soil here in Kentucky (like anyplace, you have to dig down under the topsoil layer to find the clay...you'll know it when the going gets tough!) I built it on a brick pedestal, with a sand base covered with firebricks as the floor (but your tiles will work fine as long as you have a good sand base underneath). I made a barrel vault style, using a sand mould, with an inside cooking floor of 24 inches by 36 inches; an entry door of 18"; and a door height of 8.5 inches. After the clay hardened for about a week, I removed the sand and lighted a slow curing fire. I now cook pizzas regularly and have never insulated the top, which is still exposed (I built a wooden A frame over it with a 6-12inch gap to keep the rain off of the clay). The oven walls are about 5-6 inches at the base, and 3-4 inches at the top (remember that wet clay flows, and if you mix it too wet as I did, you will get some flowing, with the bottom ending up thicker than the sides. But no matter, it still works great!). Finally, on the insulation question, it takes about 2-2.5 hours to fire up, and I do keep a fire buring in the back of the oven at all times, so that I can increase the heat by adding a small piece of wood right before cooking the pizza, which works fine. (I have even burned the bottom of some initial pizzas by getting the oven too hot). The only thing this oven won't do is cook over 2-3 days later as the brick ones will, but I only use it for pizzas (90 seconds to 2 minutes depending on the heat) and some barbequed meats (covered with foil and a door on the oven overnight). If you can't find my pics on this site, let me know and I'll post some more. Happy building!!!

[dmun]

Re: low dome clay oven

A brief note, not to get into an argument: Kentucky is covered in forests, where the UK was pretty much deforested by the 18th century...

[luca]

Re: low dome clay oven

Here is the thread with pics on the clay oven:
http://www.fornobravo.com/forum/f3/c...eferrerid=6655

As for clay in the UK, the best way to find out is simply to dig! (I read somewhere that you should be able to make a fist sized ball with the clay, and then drop it from waist height without it falling apart; then you know that it has the cohesive properties necessary to be made into an oven. I did this and found that it was true!).

[Archena]

Re: low dome clay oven

Devon* is considered prime 'cobbing' country (houses instead of ovens!) and is still where you find the most cob houses including those dating back to the 16th century!

I live in the danged Black Belt - and reach clay in only one shovelful!


*AKA Devonshire - beats me as to which one to use when - I'm from Alabama, not Britain.
**None of the above has much to do with anything but I'm in a trivia mood!





I'm staying neutral in the insulation wars - I've read good cases for both sides.

[marklewis]

Re: low dome clay oven

Did you ever build a clay oven???
Check out my tread link: I built one and have used it and will next be insulating the dome. I have some expertise and may be able to help answer your questions.

http://www.fornobravo.com/forum/f43/...ild-12388.html

[jpmort]

Re: low dome clay oven

Hey, thanks for the question. Much has happened and I have decided to go the easy route. I think I jsut thought of getting everything sorted was just too much, however much I would have liked to make my own. I kept going back to using bricks to make an over that heats up enough to do the pizzas I like - 60 to 90 seconds. So, I was looking at what was available off the shelf, and I have gone for a ready made oven. I have jsut installed it and have used it four times, not enough to give any real feedback as I am still learning how it works.

So, I am disappointed with myself for not making one, but recognising that if I carried on with that desire, I would be here in a years time still thinking about it!

But I am still interested and going to look at your link

John

[luca]

Re: low dome clay oven

I'd be interested in your comments on what oven you chose and why. Also what your impressions after four pizzas. We are all still learning here!

[jpmort]

Re: low dome clay oven

Well, thats a good question. I some specific requirements:
1. I only make a few pizzas at a time, between 2-4. So, I dont need lots of retained heat. Whats important here is speed to heat up, and be able to heat up to the right temperature for around 15 minutes.
2. Space restriction. I dont have much space for the oven so the minimum size for making one pizza at a time is important.
3. I want to bake Napoli type pizzas, high heat, 60 to 90 seconds. I am not interested in cooking anything else in the oven, no breat or meat.
4. It is wet here, and the winter means 95% humidity all the time. So it has to be able to resist that wet whilst not having a roof over it.

So, what I concluded is that a low dome is very important for high heat and rapid heat up. I could not work out how to make a low dome and make it out of clay easily without it collapsing. In addition, the round oven is optimal for the requirements I have.

The waterproofing requirement meant that clay was going to be tricky. There are ways around it but it jsut added to the complexity.

What I went for is one that is designed by someone who used to work in building commercial ovens. The oven is made of modern refractory materials, and the insulation is effectively on the inside! There is no heat retension inside. So the oven fires up rapidly. In addition is weighs around 30kg, so it can me lifted easily into place by two people. And after a few firings, it can be left out exposed to the elements. No foundation or preparation required!

Internal width is around 56cm/22in, length 63cm/25in. This is JUST enough space for a pizza and a fire at the same time. If I could choose, I would have the width a little wider.

I use a thermocouple to measure temp and at the moment it takes around 60 -70 minutes to get to the right heat. Mainly because I am not very good at lighting the oven. I have also fitted tiles on the cooking surface to provide some retained heat, and consistency, because I found the temperature in the original design created varying results over a short time. I also do some ciabatta type bread and roast coffee beans when the oven is cooling.

So, thats where I am at, and I am very happy with my decision. If I had clay easily available, the weather was better, and had some more space, I might have tried a clay oven

I am attaching a pic...

John

[luca]

Re: low dome clay oven

Thanks for the quick reply; I am especially impressed by your heat-up time! The only negative I see in this commercially-built oven is that it has no floor for retaining heat to make the bottom of pizza/bread nice and brown. I wonder if you set the oven on a layer of fire bricks or similar heat sink (maybe even cement board) whether this would help with the heat mass issue?

[jpmort]

Re: low dome clay oven

Hi,
What I have done is to put some glass fible insulation below the oven, and then placed the oven back. This has given me far better heat retention. The last time I tried, i got the oven too hot and the pizzas got a little black!

john