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My 30" Homebrew Castable WFO Build

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  • #16
    The Curing Process and Insulation Blanket

    After waiting 7 days for the cast to cure, I began the fire curing process.

    On the first day, using a commercial halogen work light with one bulb (of 2) on I was able to hold a temperature of 150 degrees F. I kept the light in overnight. On the 2nd day I turned both bulbs on and was able to get the temperature up to 200 degrees F. Again I left it in overnight.

    On day 3 I made a small fire and tried to keep it at 300 degrees F, although I admit the temperature fluctuated to a higher temp before come down to my target temperature.

    Day 4, I moved to a bigger fire and a target of 400 degrees. Again it got higher and then regulated to my target temperature. I tried to keep it at the target for at least an hour. Day 5 500 degrees, (the pictures show the black turning to white as the oven heated.

    Day 6 - 600 degrees. Day 7 I went all the way and got it up to 800 degrees and we made our first pizzas.

    I confess that throughout the process I was very excited and probably pushed the temperature quicker than recommended, but in the end it didn't bite me in the butt. First impressions of the way it fired was that the smoke was drawing beautifully through the flue. I noticed smal hair line cracks on the inside of the cast, but there were none on the outside of the dome and no smoke.

    Temperatures with the thermal blanket on the outside rose to about 120 degrees F and after making pizzas the underside of the cement board was about 135 degrees F.

    Next step the Perlite Insulating layer.

    Ted

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    • #17
      Perlite Insulating Layer

      After taking some time to use the oven, it was time to get the next step completed so that it can be fully ready for winter.

      My intent was to use the 10:1 ratio of Perlite/vermiculite mixture to Portland. I also added some lime and fireclay to help with workability. Honestly I found it quite difficult to work with and started work down to more like an 8:1 ratio. It was especially difficult on the first layer for the mix to adhere to the dome where it was basically vertical.

      On the second coat I opted to go with the 8:1 ratio from the beginning and found it worked better and I guess my trowel technique was also improving.

      Had another pizza bake and found that I was getting about 115 degrees F at its hottest on the dome.

      Next step Tiling the base and the front of the oven.

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      • #18
        Tiling the Base and Fascade

        Getting to this point has been very time consuming. I knew I wanted to use porcelain tiles but found that the Mosaic size tiles were extremely expensive and I didn't want to blow my budget. Finally I found a fairly generic Italian porcelain tile at a great price and decided to do the broken tile piece Mosaice.

        I used thinset as a base and place the tiles in a random pattern. I then used Sanded grout.

        After taking such a long time to figure out this step, I was presently surprised how simple the process was and the end result was striking to me.

        Next Step - Stucco Render

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        • #19
          Stucco Rendering.

          My plan is to do a simple concrete Stucco and then once it is cured paint the stucco to seal it up.

          To this point I have done all of the steps myself, but at this point I wanted my friend Mohammed, who is a refugee from Syria and who does stucco for a living, to do this final step.

          He used Quikrete Mason Mix Type S and did one coat of about 15mm.

          That happened on Monday and now Today Thursday we had our first snowstorm of the year. So I guess the painting will have to wait until next year.

          That's all for now. Thanks again everyone for this forum and all the great guidance and wisdom.

          Ted

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          • #20
            This is a bloody good effort. So many "cast" ovens are shoddy half arsed affairs. This is damned good.
            Clearly you understand all the principles and you get that casting your dome doesn't mean throwing everything else out the window

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            • #21
              Thanks so much for documenting your build so well. It will serve as good help for others to follow. I am a little surprised that you escaped damage to the inner casting seeing you didn’t add any burn out fibbers to the inner dome mix and you then proceeded to drive out the water from it in an uninsulated state.
              Regarding the 10:1 vermicrete application the first 6” or so, when staring from the bottom is quite difficult as it doesn’t like to stand up vertically. You can do that first but, allow it to set for 24 hrs so you have something firm underneath to build on top of. The set mix can easily be carved away if it’s a bit rough. The trick is to make sure it is flat on top so you have a decent ledge to build on to. As you rise higher it becomes much easier because it slopes in. The addition of more cement reduces the insulation capacity, but a little powdered clay added to a 10:1 vermicrete makes workability much better. Sorry, too late for this advice now.
              Kindled with zeal and fired with passion.

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              • #22
                Thanks David. I have been inspired by this forum and all the great projects. At the same time I learned so much from all your ideas and sage advice. I hope my build will become part of the inspiration of this forum.

                One clarification. Although I think my pictures may have given the wrong impression, I didn't do any curing fires until the casting was covered by a 3 inch layer of the thermal blanket. So I might have been fortunate in leaving out the fibres, I didn't press that luck too much.

                Your ideas about starting from the bottom makes a lot of sense, and I do recall seeing that advice at one point on the forums, but I guess it didn't get imbedded in my thinking on that day.

                Thanks again for everything. Enjoy the your spring time and oncoming summer. It looks like an early winter for us here in the centre of Canada.

                Ted

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