Author Topic: Building a Traditional Clay Oven  (Read 31073 times)

Offline Synaptoman

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Building a Traditional Clay Oven
« on: October 11, 2009, 10:08:23 AM »

I have embarked on a project to make a traditional clay oven. The design is thousands of years old and ruins of clay ovens have been found on all of the continents. Because I hate doing things normally, I decided that my clay oven would be built on a timber base and stand proudly on my deck, where the whole family could help with the bread baking, pizza making etc.
Here is a shot of the finished frame, which I suppose I have over-designed (again). It offers a sturdy base with the weight evenly distributed across the bottom.



My main concern was to keep the heat contained and the underlying timber very well insulated from heat of any kind.  The base is made with a timber decking floor insulated with a sealer which can apparently withstand 1200 deg C.  We will be testing this !!



As you can see on the right of the image, the bricks will stand slightly higher than the frame.  
« Last Edit: March 14, 2010, 03:29:31 PM by Sister Wolf »
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Offline Synaptoman

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Re: Building a Traditional Clay Oven
« Reply #1 on: October 11, 2009, 10:16:35 AM »
Two steps forward, one step back.  After adding 200-300kg (440-660lbs) more weight, I decided to consult a retired engineer, and after much discussion came to the conclusion that there was no way that the deck would hold close to 400kg (880lbs)

At this stage I stripped all the brick paving as well as the sand underlay and with the help of my son moved the base to another (hopefully stronger) deck.  Then I relaid the bricks, built the door frame and moulded the sand form that defines the inner volume of the oven.  The door height must be preciisely 63% of the inner dome height.  Another important measurement is the ratio of dome height to base diameter.  This should be between 60 and 75%.  Here are my final figures.

Door Height = 300mm (12 inches)
Dome Height = 476mm (19 inches)

Ratio = 63%

Base Diameter = 795mm (31 inches)

Ratio = 60%

This should work.  Here are some images of the project as it stood at that stage.

I built a little timber deck for the top of the door frame to rest on while I cemented it in.



Here is what it looked like cemented with the inner sand form in the background.



This is what the sand form looks like.  This now gets covered with wet newspapers and the first (inner) layer of clay mix gets plastered over it.


When your only tool is a hammer,
everything looks like a nail.



Offline Synaptoman

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Re: Building a Traditional Clay Oven
« Reply #2 on: October 11, 2009, 10:22:49 AM »
With a beautiful Saturday morning dawning and the Child Bride off running a half marathon, I could really get moving with the clay oven project.

Step one was to cover the sand form from the day before with some wet newspapers (after re-checking my calculations.)



Next I measured out 1 part clay to 2 1/2 parts building sand.  I have excavated the clay from my terraced garden, dried it out, crushed it into a fine powder and removed all stones.  Here is the dry material before mixing.  As you can see I mix on a piece of plastic.  It's then easy to pick up one side at a time and roll the mix to the center.



Then some serious mixing involving the traditional "gumboot dance".    Add water as needed to try and get a final consistency that results in a firm (not too dry and not too wet) mix that should look something like this.



One then works from the bottom up around and around the newspaper covered sand form.  Roll a handfull of clay mix, put into place push inwards, push downwards, repeat.  I smoothed off the surface after every revolution.  This layer (the inner layer) I have made about 60mm (2 1/2 inches) thick.



The completed inner layer looks like this.



I left this overnight to harden.  It is not in direct sun and I'd prefer it to dry slowly, which should prevent too much cracking.   The oven is expected to crack in places and one must just fix these cracks as the occur.  Other builders have suggested only 3-4 hours before the inner sand form is removed but I think that this is because they have to cut the door aperture.  My plan is slightly different and I can't see any harm in leaving the sand form in longer. 
When your only tool is a hammer,
everything looks like a nail.



Offline Synaptoman

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Re: Building a Traditional Clay Oven
« Reply #3 on: October 11, 2009, 10:25:40 AM »
The moment of truth arrived.  I tentatively removed the yellow board holding back the sand form and then carefully pulled out the support holding up the door frame.  Nothing moved, broke or sagged.............initially.



Then just at the top right of the door, the edge of the inner layer started to sag.  I quickly propped it up with one of the supports that I had use for the door frame and proceeded to dig out the sand.  It was like opening an egyptian tomb for the first time.



After the sand had been removed, I lit a candle to very slowly dry out the walls.  You can see the prop holding up the sag as well as pieces of wet newspaper still sticking to the walls in the next image.



I left this burning the whole day and then in the early evening started a very small fire.  As the inner core slowly heated and hardened I was able to take the prop out and spent a few hours (with a quite few glasses of wine) slowly and carefully feeding this fire, until the whole outside of the oven was warm to the touch.


When your only tool is a hammer,
everything looks like a nail.



Offline Synaptoman

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Re: Building a Traditional Clay Oven
« Reply #4 on: October 11, 2009, 10:29:44 AM »
The second layer of the clay oven is an insulating layer.  It consists of the same clay/sand mix described previously but with the addition of an insulating material.  I decided on straw.  This mixture is known as a "cob" mix and has been used in building and insulating for thousands of years.

Here is what the mix looks like with the straw sprinkled over the top.



It then gets well mixed into the clay/sand.



The cob mix is then made into bricks and built up around and around the inner layer.  I have made this layer also about 60-70mm (2 1/2 - 3 inches).  As you can see from this image, the inner core has hardened to a strong smooth finish.



The layer is then slowly built up, pushing down, pushing in and then smoothing after every revolution.



This is a pretty rough layer with straw stalks sticking out all over the place.  This is not really a problem because a final finishing layer of about 30mm will seal off everything nicely.

I am busy firing the oven again tonight and the insulating layer appears to be drying and hardening exactly according to plan.  Steam is rising off of the wet clay.  The "63%" door opening is working like a charm.

I  should have the insulating layer hardened enough to complete the finishing layer before the end of the week.  Now I just need to make the door and possibly varnish and seal the timber stand and we'll be eating bread and pizza made in the oven by the weekend.

When your only tool is a hammer,
everything looks like a nail.



Offline Synaptoman

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Re: Building a Traditional Clay Oven
« Reply #5 on: October 11, 2009, 10:33:44 AM »
With the insulating layer completed, I proceeded to fire the oven every evening.  As the inner layer gets harder, you can build bigger fires and raise the inside temperatures.  The insulating layer fired well and the temperature caused the straw in the clay to almost char and we could smell it quiet distinctly.  Also you could see the burnt straw on the surface of the clay so it must have got very hot.  Some minor cracks developed (probably because I dried it so quickly), but these I patched and then proceeded to the final (finishing) layer.

This is a clay/sand mix the same as the inner layer but is only about 30-40mm (1-2 inches) thick and is really just to finish off the oven nicely.  You build it identically to the other layers and work your way around and around placing the mix, pushing down, pushing in and repeating.  Here is what it looked like.  Note the insulating layer showing from underneath.



As you can see the oven now reaches almost to the end of the frame.  The walls are now over 150mm (6 inches) thick and this should allow me to achieve some impressive inside temperatures.

I fired it once again and this time a lot of cracks developed because this final layer is thinner and also I worked in gale force winds which dried it out far too quickly.  I decided to plaster the floor of the oven with the clay/sand mix as the brick paving floor wasn't smooth enough to get pizzas in and out.

The rustic door was completed and the door frame plastered so that the door sits snugly in the frame.  The last thing to do was to put my signature (hand print) above the door and voila, the oven was finished.  The hand print is a pagan touch and apparently man's first signature.  Hand prints were put over traditional oven doors to protect against the "evil eye" and bless the food that was to be prepared.   Well here is the completed oven.



When your only tool is a hammer,
everything looks like a nail.



Offline Synaptoman

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Re: Building a Traditional Clay Oven
« Reply #6 on: October 11, 2009, 11:05:54 AM »
Well the oven looks good, it's dimensions are correct, it seems to fire OK and hold it's heat.  But does it work?  Well today we set out to prove (or disprove) a theory that you can make an oven out of clay from your own garden.

Step One was to start a fire.  We built it up about two hours before the cooking and slowly got the clay up to a decent temperature.  Then we made the pizza bases (12 in all).



Everyone then built their own pizzas using tomato, cheeses, spinach, feta cheese, salami, onions, mushrooms, bacon, ham, spicy chicken and numerous other delicious toppings.

Then they were popped into the now scorching hot oven using a hastily made pizza paddle (made out of a recycled road sign !!)  This is what the first pizzas looked like in the oven.



Here is a shot of my two "assistant chefs" hard at work.



And here is what the first pizzas looked like on the plate.



After the last pizzas were cooked I popped some bread rolls in and closed the door to see how it baked.



The overall verdict was a big thumbs up.  This is certainly a great way to spend a long lazy Sunday with family, good friends and a good few glasses of red wine.

When your only tool is a hammer,
everything looks like a nail.



Offline smittymojoe

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Re: Building a Traditional Clay Oven
« Reply #7 on: October 11, 2009, 11:55:38 AM »
Outstanding post Synaptoman!! Thanks for taking the time to put this together. I would like to take this up a notch and build a bigger oven outside on a 14' x 14' pave stone patio in my backyard.

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Offline bubtech

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Re: Building a Traditional Clay Oven
« Reply #8 on: October 11, 2009, 12:07:06 PM »
This thread has been selected as a “best of” thread by BUBTech.  You can search for “best of” threads by using that term in the search mode.  Everyone on the forum is encouraged to reply to a post they think is “best of” worthy so we can all search for them.  For more information on the “best of” thing, see  http://thesurvivalpodcast.com/forum/index.php?topic=3423.0
New Podcast www.momenttoponder.com Similar and inspired by no less than Jack Spirko.  I try not to rip him off too much ;).  Momenttoponder is a single subject per episode short format (30 minutes or so) once or twice a week.  MTP is more of a "beginners" podcast focused on baby steps in not only preparedness but philosopy and life in general.

Offline Darkwinter

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Re: Building a Traditional Clay Oven
« Reply #9 on: October 11, 2009, 05:06:12 PM »
Excellent Post!!! Thank you for taking the time to share that with us. +1
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Re: Building a Traditional Clay Oven
« Reply #10 on: October 11, 2009, 05:15:33 PM »
Very nice!
+1 from me too!
Great post!

Offline P_Coltrane

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Re: Building a Traditional Clay Oven
« Reply #11 on: October 11, 2009, 06:43:55 PM »
Very cool!! I am completely impressed (and a little bit inspired).

Offline firetoad

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Re: Building a Traditional Clay Oven
« Reply #12 on: October 11, 2009, 07:11:40 PM »
Awesome!  +1 most definitely!

Offline Synaptoman

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Re: Building a Traditional Clay Oven
« Reply #13 on: October 12, 2009, 12:33:17 AM »
Thank you all for your kind words.
When your only tool is a hammer,
everything looks like a nail.



Offline Roswell

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Re: Building a Traditional Clay Oven
« Reply #14 on: October 13, 2009, 07:09:39 PM »
+1, great documentation!  That pizza looks delicious!
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Offline Synaptoman

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Re: Building a Traditional Clay Oven
« Reply #15 on: October 13, 2009, 10:42:11 PM »
My next step is going to be to build a waterproof cover to protect it from the elements and then try baking different breads and roasting meats and smoking various foodstuffs. 

For the smoking process I am going to build another door with vents top and bottom.  The bottom vent will be to draw oxygen in to keep the fire going and the top will be to vent the excess smoke.  This will require some experimentation as I'm not too sure of the ovens smoking capabilities.  The historical records merely referred to it's use as a "smoker".

Any suggestions here would be appreciated.
When your only tool is a hammer,
everything looks like a nail.



Offline cohutt

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Re: Building a Traditional Clay Oven
« Reply #16 on: October 14, 2009, 04:19:57 AM »
+1

dayamn!


Offline cohutt

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Re: Building a Traditional Clay Oven
« Reply #17 on: October 14, 2009, 04:34:12 AM »
damnit you got me thinking......


I've seen some designs that were less precise than yours as far as height to width ratio and the height of the door vs overall interior height. 
These include accommodations for a chimney behind the door and tended to be wider and flatter than your design.

Am I right to assume that the ratios you give allow for an oven that:
1. provides for proper drafts both inward and then outward through the door without the need of a separate  chimney?
2. is therefore more efficient and easier to drive to the higher temperatures using less wood?




Offline Synaptoman

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Re: Building a Traditional Clay Oven
« Reply #18 on: October 14, 2009, 06:12:37 AM »
Quote
Am I right to assume that the ratios you give allow for an oven that:
1. provides for proper drafts both inward and then outward through the door without the need of a separate  chimney?
2. is therefore more efficient and easier to drive to the higher temperatures using less wood?

You got it !!  The absence of a chimney makes it thermally FAR more efficient.  Get the ratio correct and you have a visible thin stream of smoke venting out of the top of the door frame.  The bottom is ice cold as cool air is sucked in for the combustion process.  The top is so hot that you cannot keep your hand there for even a second or two.
When your only tool is a hammer,
everything looks like a nail.



Offline Synaptoman

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Re: Building a Traditional Clay Oven
« Reply #19 on: October 14, 2009, 06:15:13 AM »
.... and that with far less wood than if a chimney were incorporated.
When your only tool is a hammer,
everything looks like a nail.



Offline Roswell

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Re: Building a Traditional Clay Oven
« Reply #20 on: October 14, 2009, 07:32:53 AM »
My next step is going to be to build a waterproof cover to protect it from the elements and then try baking different breads and roasting meats and smoking various foodstuffs. 

For the smoking process I am going to build another door with vents top and bottom.  The bottom vent will be to draw oxygen in to keep the fire going and the top will be to vent the excess smoke.  This will require some experimentation as I'm not too sure of the ovens smoking capabilities.  The historical records merely referred to it's use as a "smoker".

Any suggestions here would be appreciated.

On the “Self-Sufficient Homestead Show” they talked about using a regular grill to make a cheap smoker. I don’t see any reason why you couldn’t do the same thing. They actually got the idea from a friend of theirs that is a championship smoker.  Basically, you take hickory chips or whatever kind of wood chips you want, soak them in a bowl of water for an hour or so, drain, then wrap in aluminum foil, poke a couple holes in the top with a fork and then put it on the grill or in your case, in the oven with your ribs or whatever and cook on a low temperature for at least 8 hours.  Follow the link below for the show

http://sshomestead.com/?p=190
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Offline Synaptoman

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Re: Building a Traditional Clay Oven
« Reply #21 on: October 14, 2009, 07:51:28 AM »
Quote
Follow the link below for the show

Thanks for that.  I'm sure it'll work.  As far as I understand, there are two types of smoking, hot-smoking and cold-smoking.  Hot-smoking involves heating (cooking) the meat and at the same time smoking it with the flavor of your chips.  Cold-smoking involves venting the smoke to a seperate smoke box and it takes a lot longer to cure because no cooking takes place. 

I think I'll stick to hot-smoking because it's safer.  I'm going to light a fire and then burn it down to a large bed of coals.  Then I'm going to put the aluminum foil bag of chips on the coals.  Suspend the meat off of the floor and then close my customized smoking door (vent bottom and top) and see how it goes.

Thanks for the tip of the aluminum-foil bag, it answers one of my major questions.  The only remaining question is, "What would they have done 5000 years ago without aluminum-foil?  ::)"

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Offline mxitman

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Re: Building a Traditional Clay Oven
« Reply #22 on: October 14, 2009, 08:10:26 AM »
damn thats sweet, I spent a month in italy and ever since have wanted to build my own clay oven for baking pizza's in...

Offline Doc Savage

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Re: Building a Traditional Clay Oven
« Reply #23 on: October 17, 2009, 02:38:23 AM »
I have a friend who grew up in South America.  He said that people down there will take meat (roast, small pig,whatever) by the bakery in the morning.  They have already baked the bread for the day in an oven similar to this.  The people at the bakery would put the meat in the oven and the you would pick it up on the way home.  Basically the meat was slow cooked all day as the oven was cooling off.  Win, win for everybody.  Great post and I am muchly inspired.

Offline Synaptoman

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Re: Building a Traditional Clay Oven
« Reply #24 on: October 18, 2009, 11:20:58 AM »
On the advise of Roswell I tried the "wood chips in aluminum foil" method of smoking in the clay oven today.  First I soaked the oak chips in water for about an hour and then wrapped them in an aluminum parcel and then poked some holes in the foil with a fork.

These are the chips I used, but I suppose any untreated wood chips would work.



I also thought about the combustion process whilst smoking and figured that the remaining coals would soon die if they didn't get sufficient oxygen so I? knocked together a "smoking door" that would allow air to be sucked in at the bottom and vent some smoke at the top. 

It looked like this.



I then built up a fire and when it died down to coals, placed the aluminum parcel on the coals and then started loading the food !!
When your only tool is a hammer,
everything looks like a nail.



Offline Synaptoman

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Re: Building a Traditional Clay Oven
« Reply #25 on: October 18, 2009, 11:32:01 AM »
I figured that there was no point in just smoking today so I really loaded the oven to see how it would hold up.  Here are some shots of some food cooked over a 5 hour period.

Smoked Mussels and Garlic Bread.



Smoked Fish (it's a fish called "Snoek" here in South Africa).



Potato Bake (this took some time).



Mini Bread Loaves.



All this from about 8lbs of kindling and wood !!

When your only tool is a hammer,
everything looks like a nail.



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Re: Building a Traditional Clay Oven
« Reply #26 on: October 18, 2009, 11:33:34 AM »
We are all hopping on the plane right now to join in that feast!  You'd better get cooking.

Offline Roswell

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Re: Building a Traditional Clay Oven
« Reply #27 on: October 18, 2009, 06:02:23 PM »
I am glad it worked out for you Synaptoman. Have you ever thought of opening a restaurant? Seriously. You obviously have quite a talent for cooking and can do it on a beautiful oven of your own making. Even in south Africa that has to be something people would pay for. Might be a good backup plan if something bad were to happen. I am salivating over that fish and those mussels.
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Offline Synaptoman

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Re: Building a Traditional Clay Oven
« Reply #28 on: October 18, 2009, 10:47:53 PM »
Quote
Have you ever thought of opening a restaurant?
We actually own a coffee shop but obviously don't cook food like this.  There is quite some demand for traditionally cooked food and it certainly moght be worthwhile taking this project further.  The food didn't just look good, it tasted great too.  I think we've just lost so much quality of life by our rished lifestyles.  Maybe the recession is teaching us some valuable lessons.

I think what I am going to do now is try and find a paying customer to make the next clay oven.  THIS could be a valuable skill if the SHTF.
When your only tool is a hammer,
everything looks like a nail.



Offline Gas-Mask

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Re: Building a Traditional Clay Oven
« Reply #29 on: October 19, 2009, 02:09:13 AM »
that food looks good!   Looks like something out of an exclusive restaurant in Beverly Hills...
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