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Tarracotta Flower Pot Oven -- using two flower pots

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  • Tarracotta Flower Pot Oven -- using two flower pots

    I've been researching outdoor oven construction but did not want to use either brick, adobe or cement....

    But since I've baked in terracotta flower pots I began to consider my options using that resource.
    This example got me thinking:

    But it's a bit small. So I thought it through -- and wondered...

    What if I used two large terracotta flower pots of the same lip circumference. I cut a upside down U opening in the bottom of one for a door opening and butted the two pots at their lip together horizontally. Now butted together, I'd support and embed them in a base of sand medium so that they were in the one horizontal plane and joined the two lips together (with?) -- something like a large squat clay cocktail shaker on its side.

    I'd build up the floor horizontally inside the pot oven (with clay?sand?) and lay down a cooking slate on top of that..

    Voila! One terracotta oven.

    A variation would be to coat the inside of each pot before I joined them with a layer of clay to increase the oven's insulation properties and maybe reduce its depth if necessary. I usually sculpt in paper clay and that may do the trick as I never fire it when I've made puppets.

    No matter because the exterior is already fired terracotta the inner layer would be protected from weathering. It would be like a tandori oven on its side but not as narrow.

    The exterior look would be snazzy terracotta.

    One issue: would this work? All of it? Only part? None?

    • some constructed support for the doorway as the terracotta opening may become brittle and crack when knocked by tools and gear passing through.
    • a little chimney hole towards the front -- made as a second opening cut in the pot either toward the top of the base or along the side wall of the front flower pot
    • Door? Use a terracotta pot saucer made for the pot size and cut across a tangent so it sat snugly overthe opening.(I could also cut an arch in a saucer to support and strengthening my oven doorway too using the saucer rim as arch support)

    In my experience working fired terracotta is facilitated by soaking the pots in water before cutting and trimming.

  • #2
    Re: Tarracotta Flower Pot Oven -- using two flower pots

    More Thoughts: I see where my joining medium could be Refractory Mortar. Whether this will be strong enough I don't know. I can nonetheless coat the exterior of the whole 'oven' in mortar as Forno Brovo suggests in its DIY section.

    So assuming I can get the terracotta to withstand the high temperatures -- and when I've ovened/baked with terracotta before it has -- then it's a question primarily, I guess, of insulation and draw/air flow. I also need to ensure that the depth isn't beyond the reach of my arm so two different sized pots -- one tall/one squat each of the same diameter -- seems to make sense such that it will indeed look like a cocktail shaker on its side.

    As for the inner coating I had in mind the approach / technique suggested by the DIY tandoori oven inside a garbage can and while I could use commercial clay, I could use Adobe instead as this inner insulation layer would shrink as it dried and with later firing and baking, pull away from the terracotta walls as it contracted inwards.When I fused the pot rims together I'd bog the join with more clay from the inside by hand and could do any amount of repair and adjustment work with added clay as required.

    The properties of paper clay -- eg: terracotta paper clay -- which is around 45% paper mix, make a lot of sense as a material of choice.

    On the 'floor' I could build this up to a broad horizontal plane by using sand and clay and a few fire bricks or a standard terracotta pizza slate -- or use a metal shelf instead. But I'd need to make the floor level with the bottom of the door opening so I could sweep out the coals.

    Further on the terracotta theme I could also bake -- eg: bread -- inside the oven with a smaller terracotta made from flower pot, with a clay saucer as a lid and the water hole bogged.

    And since I may mortar the outside of the oven I can mosaic it if I want to with the presumption, touch wood -- that the underlying structure of terracotta pots will remain stable and won't drastically contract or move.


    • #3
      Re: Tarracotta Flower Pot Oven -- using two flower pots

      Most interesting! Keep us updated!

      Sometime ago I purchased a large (19 1/2 inch inside diameter) Italian clay pot with a hemispherical shape with the idea of inverting it and setting it on bricks and putting some sort of inexpensive heat sink over the whole. I haven't found the time to try it... yet!


      Question: do you wish to be refered to as "Rat" or "Rat Bag" or do you have a name?


      • #4
        Re: Tarracotta Flower Pot Oven -- using two flower pots

        Yes I do have a name: Dave Riley. I usually sign my posts ....


        • #5
          Re: Tarracotta Flower Pot Oven -- using two flower pots

          I've had a rethink...and since I have a very large terracotta pot -- 60cm diameter and a depth of 45 cm -- I'm thinking that the weakest feature of my original concept was the joining of the two pots. Too much can go wrong.

          So if I invert this single pot, and cut a door in the side -- just like the image I shared above -- I've got more control over the project.

          I'll use a carbide grit saw blade to cut the pot ( but have to decide on the door's shape and width) . So what's that? $5.00 , a few hours work and a couple of blisters.

          I then make a clay and perlite mix -- per this approach -- 85% Perlite: 15% clay -- and layer that on the inside of the upturned pot.

          Since I can expect at least 10% shrinkage I'll need to layer a bit extra as the lining dries but I'm unsure how best to do this with a Perlite/clay mix . I'm also hoping that the mix will form around the sides of the pot despite shrinkage. (When using Paperclay it's easy to simply lay clay over clay before any firing but I'm not sure how a mix like this. will perform.)
          An option would be to carefully do this in stages, forming a series of 'bricks' or just rims in situ (as one would coil a pot in clay anyway)and allowing each row or coil to dry a bit before creating the next row.
          So that's a bag of Perlite --$13- $20 (fine grain? expanded medium?) and a slab of Terracotta clay from a potters supplier-- $7.00 .

          I'll use at hand bricks or pavers on a base of sand and use the same clay/perlite mix to mortar them into place.

          My hope is that after consecutive burns I can bog up the Perlite/clay lining and build up the floor as shrinkage occurs.

          It may happen -- touch wood -- that if I can make a stable horizontal base and the lining stays in place I can lift and remove the pot/oven from the base for cleaning or whatever. So it could be portable at a pinch.

          If I can cut out the door/opening in one piece, I can perhaps consider drilling it and attaching a handle and -- with the clay/perlite -- make a door jam to but it from falling forward into the oven chamber.

          It seems to me, though that it would be a good idea to bury the outer circumference of the base in some medium that could be simply swept or shoveled into place. Perlite again perhaps --at the bottom of the chamber I don't want a draft.

          I also like this idea of recycling a tire for the base:

          How cool is that! I use tires for various odds and sods around the place anyway.

          (Thanks to The Breadhunter's Blog -- great blog!)

          dave riley
          Last edited by ratbagradio; 07-29-2009, 05:23 AM.


          • #6
            Re: Tarracotta Flower Pot Oven -- using two flower pots


            Either I'm mis-reading or simply simply do not understand, but why are you wanting to place insulating refractory (your link to perlite/clay mix) on the inside of your pot/WFO? I would think that you would want to increase the thermal mass by adding to the outside of the pot (thus maintaining the largest inside diameter) and then insulating over that added material.



            • #7
              Re: Tarracotta Flower Pot Oven -- using two flower pots


              I take your point but my thinking was that if I added unstable medium to the inside it would be protected from the weather and I'd retain an exterior look that would also hold its integrity without the threat of flaking, pealing and such as that medium would be protected behind the terracotta shield.

              I live in a sub tropical climate here in Brisbane.

              As for the internal oven volume -- I'm assuming that the key aspect is the diameter at the base and given that my usage would extend to pizzas, at most two breads at once, & my dutch oven or similar slow cook(eg: Tagines)-- I wasn't planning on creating a large dome to heat up. One that could hold my preferred menu items and a suitable fire seemed to suffice.

              So if I began with a base circumference of 50 cm (approx 20") and lost another 5-10 cms to insulation material as suggested I still had a cooking surface area of 40-44 cm . Is this too small for general ab hoc use do you think?

              I also have a lot of height, as this isn't a dome -- so I could also place a rack inside the oven if I needed to . Relative to my kitchen domestic oven ( electricity) that I cook every day in -- this is larger by a factor of one half at least.

              This is an occasional, beginners oven -- not a major project (thus I'm not planning to spend many $$$$ on it.) Inasmuch as I have had any wood fired experience -- I've cooked pizza in a community mud brick oven we built at our local arts centre (very small it was too) -- but I still fed 35 with a succession of pizzas.

              I'm thinking that once I get it to working order I can customize, by adding material to the outside, maybe as you suggested.

              This all began because we were doing up our kitchen and I was without cooking facilities for weeks. So I was preparing food on a throw together bbq using my preferred material -- wood under a hot plate. I hate using charcoal because it's so fiddly and often delivers cold food.

              Domestically I'm always cooking in Dutch style ovens and I often bake bread in terracotta pots.

              Since I have also trimmed back a lot of domestic trees I now have a good wood supply.And in our limited space we just parted with our above ground swimming pool and there is a big space -- a big hole actually -- just out from the veranda.

              So one thing led to another...."Why not a wood fired oven," says I," and preferably one I could move around if necessary?"

              When I started thinking this through I was exploring Dutch Ovens -- cast iron ones for the camp fire -- where you laid coals on top of the lid as well as below. But the problem there is that for baking or slow cooking you really do need charcoal/briquettes for your fuel medium as wood offers unreliable and uneven heat. Or you need to bury the oven in a pit with the fire and maybe stones -- like a hangi

              (While I love to wrap and prepare food in banana leaves (or aluminum foil-- it's an all day affair of preparation. and very fiddly.)


              • #8
                Re: Tarracotta Flower Pot Oven -- using two flower pots

                I think that terracotta flower pot oven is awesome! What a great idea - You can buy huge ones.
                My floor is getting ready to be laid (again - ack!) but why not just get a huge flower pot - maybe cut down to size, if need be, with an opening - the only other brick work would be the opening and vent?
                Then insulate the whole thing.
                Although, the thickness of the terracotta might not be great for holding heat for a long time...but then that's where the insulation thickness comes in....
                what a great idea....


                • #9
                  Re: Tarracotta Flower Pot Oven -- using two flower pots

                  A terra cotta flower pot is typically pretty thin. It may not have enough mass to absorb and reflect heat down on you cooking floor. Also, terra cotta is not the best oven material. Like plain brick, it may crack and chip, or spall.
                  My geodesic oven project: part 1, part 2


                  • #10
                    Re: Tarracotta Flower Pot Oven -- using two flower pots

                    I was thinking of the terra cotta covered bakers I've been using in my regular ovens for baking bread.
                    I was also thinking it would be kind of a fun quickie thing to do to experiment with the baking of bread.
                    But not to worry - the floor of the brick oven, once again, is coming along nicely, and I will have brick dome on top and not a terra cotta flower pot!


                    • #11
                      Re: Tarracotta Flower Pot Oven -- using two flower pots

                      How about trying it small scale first? Get a cheap, small pot, fix it and see if it will bake a muffin.

                      Alton Brown made a smoker from two terra cotta pots so it might just work.
                      "He is no fool who gives what he cannot keep to gain what he cannot lose." - Jim Elliot

                      "Success isn't permanent and failure isn't fatal." -Mike Ditka


                      • #12
                        Re: Tarracotta Flower Pot Oven -- using two flower pots

                        Originally posted by Archena View Post
                        How about trying it small scale first? Get a cheap, small pot, fix it and see if it will bake a muffin.

                        Alton Brown made a smoker from two terra cotta pots so it might just work.
                        Talk about baby steps - a muffin, that cracks me up (great idea though). Which brings me to topic - I agree with David, the terra cotta we have in the states are way to thin to be subjected to repeated heat that your oven will see. I would also be cautious where it came from - some countries don't give a damn what materials they throw into it. I can see it working as a smoker because mine runs around 180 deg F - not even close to the temps you will see firing it to what your pizza wants.


                        Last edited by Les; 09-12-2009, 06:14 PM.
                        Check out my pictures here:

                        If at first you don't succeed... Skydiving isn't for you.


                        • #13
                          Re: Tarracotta Flower Pot Oven -- using two flower pots

                          I can't take credit for the muffin idea. I'd read it from a guy who made several to try different mixes of cob.
                          "He is no fool who gives what he cannot keep to gain what he cannot lose." - Jim Elliot

                          "Success isn't permanent and failure isn't fatal." -Mike Ditka


                          • #14
                            Re: Tarracotta Flower Pot Oven -- using two flower pots

                            I've built my terracotta pot oven and am currently curing it. The one drawback so far is that because I layered a terracotta clay and perlite mix around the pot the mix shrinks over the underlying pot shape so cracks form in places which you need to render and fill with fresh mix.

                            You always get shrinkage with clay I gather of some 12 or 15 percent depending whether it's green ware or whatever -- so when you are covering a large area this is going to happen as the coating dries. This is why , I assume, layering clay inside a tandoori shape is less problematical.

                            [My original idea was to layer the clay mix inside the oven while the pot was upright and then invert it for baking on a flat hearth of bricks. But to make that worthwhile you really do need a large pot and two sets of hands to upturn the pot layered with clay-insulation mix.]
                            But the design concept seems to far. When I start baking I'll let you know.I have had a few big fires in the oven without any problems with the original clay pot. (If the pot does crack -- well then the dome remains as it in effect served me as form work).

                            The other advantage , which I'm adapting, is that when you cut your door shape in the pot -- the first thing I did by using a file(easy it was too)-- you get a customized door. All I need to do is add a handle and push the cut out section into the door jam to lock in heat.

                            Now if you were really taken with this notion, I expect you could cut yourself a door in a large pot and bury it in an embankment and try to harness the ground's thermal mass.(Or cover it with stones so long as they don't explode!) Your standard mud brick oven is really that...So if you wanted a quick oven, considering how the Maori create a hangi because with have-pot-will-travel --there's a quick and portable one right there. Lighter than a dutch oven too!

                            You could go bush baking with your terracotta pot and I guess even bury smaller pots in the campfire coals!
                            Just one further note on terracotta -- and I use it for sculpting occasionally -- the much admired Moroccan tagine pot with its unique conical lid is more correctly used on top of the fire/heat source rather than inside an oven. So you are applying direct heat to the terracotta base and using the terracotta conical roof to transfer heat throughout your casserole. But check out a tagine design and thinness and ponder the possibilities of terracotta... but reemmber with tagine on top of the stove you soak then m in water first.
                            dave riley
                            Last edited by ratbagradio; 09-13-2009, 01:11 AM.


                            • #15
                              Re: Tarracotta Flower Pot Oven -- using two flower pots

                              David R,

                              Very intersting concept,, Hope it works out as Im really curious and would love to build a 2nd, little oven like you describe just to try it,,, Maybe the alton brown model