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  • Castable Pizza oven Smoker combo

    Hi all,

    Im new to the forum but have read many posts on here. I have been exploring making a pizza oven from vermiculite similar to many that have been made on youtube.

    However, my concerns are this:

    as i want to use this as an oven from time to time as well, vermiculite wont have the thermal mass to retain the heat? if im reading all this data correctly.

    So i was thinking, what if i8 make the outer cast as in the youtube videos out of vermiculite and then use this to make an inner mold of castable refractory?

    If i was to do this how thin could i go for it to still retain sufficient heat / strength to hold up to heating and cooling ?

    I was going to have an offset fire box for the smoker combo part just in case people are wondering and two doors one for when im smoking (inner door) and and outer door for other times.

    The reasons i am considering this path as i quite like the idea of casting the oven chamber rather then bricks, in addition bricks are challenging to get in Brisbane, Australia and or are very expensive.

    So i guess to summarise my questions

    1) should i just build this from vermiculite? or the vermiculite refractory shell combo?
    2) if not how thin can i go to retain the heat for the inner shell? bearing in mind it will have an outer shell of vermiculite and probably a heat shield inbetween the shells.

  • #2
    Vermiculite is an insulating material, not a refractory material. Not sure where you are getting the idea that its a good material for a pizza oven, but it is the opposite of a good material for a pizza oven. You want a material that retains heat.
    My build progress
    My WFO Journal on Facebook
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    • #3
      Just to clarify Deejay's response. Vermiculite IS a good material for an oven, but only for insulation. Fergo, you need mass ( i.e. brick, refact material, etc... ) Once that has absorbed the heat, you want to retain it - that's where the vermiculite comes into play. As far as thickness of your refractory wall - that depends on what you want to do. If it's just pizza, 1 inch would probably work. If you want to cook something 3 days after the fire - you need mass.
      Check out my pictures here:
      http://www.fornobravo.com/forum/f8/les-build-4207.html

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

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      • #4
        I know the videos fergo is referring to and they do indeed show pizza ovens being made just from vermiculite and portland cement, slapped on over a form.

        Fergo - there are lots of builds on youtube, some are good but others are not so helpful. Some of the designs and materials used are imo poor choices. I would ignore the videos and spend some more time on this forum, going through as many build threads as you can to get a good idea of the principles of good oven construction.

        I'm sure one of the casting experts on here can help you with specific advice if you want to go that route. It won't be quite as easy as some of the videos suggest but performance and longevity should be much better.
        Last edited by jonv; 12-07-2016, 01:49 AM.

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        • #5
          Hi all,

          thanks for the response. I guess half of my question has been answered that i cannot make the oven just from vermiculite as it wont have the thermal mass. which i kind of figured but its nice to have this theory validated.

          Which leads to the second part of my question. If i make a mold from vermiculite and then use castable refractory cement on the inside, how thick will it need to be to gain enough thermal mass.
          As far as what i am likely to do it in, ribs, maybe bread. not three days later but maybe the next day.

          so if i was to do say 2inch thick vermiculite dome, then cast say 2inch refractory castable inside would that retain the heat im looking for?

          The reason i am looking at this route as fire bricks are not terribly easy to come by where i am, and if they are they are expensive.

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          • #6
            Both vermiculite and perlite will withstand up to 1100 C. Anything north of that and they self distruct. As a WFO will only see temps of 600 C at tops on the surface facing the fire then they are both suitable for this application. However, when you add either of them to a mix they drastically reduce its strength. This results in a refractory mix that is susceptible to abrasion damage and fracture from minor impacts, especially if it's thin. In addition if Portland cement is used it won't be too long before the casting fails as Portland cement begins to give up at anything north of 300 C. You could use Portland/lime (home brew) for an improved result or better still use calcium aluminate cement (expensive). As previous posters have advised a dense castable refractory is a better solution, usually 2" thick which will heat relatively quickly and is enough thermal mass to allow retained heat cooking (roasting and baking with door in place). You can then add insulation layers over the top, either blanket, lean vermicrete, or both.
            Kindled with zeal and fired with passion.

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            • #7
              ok sounds like i might have to just keep my eye out for some cheaper firebricks and make it out of brick. thanks all

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              • #8
                Originally posted by fergo View Post
                ok sounds like i might have to just keep my eye out for some cheaper firebricks and make it out of brick. thanks all
                I am sorry if my previous post has put you off casting your own, that was not my intention. There have been many successful home built cast ovens that are way faster and cheaper to build than a brick oven. Research the forum to find examples. Search cast ovens. The easiest way is to cast over a sand mould and create a one piece dome. As previously mentioned there are a variety of options to use as your castable.
                Kindled with zeal and fired with passion.

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                • #9
                  No worries i will think over the options and look at some castables on here and decide which way i want to go.

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                  • #10
                    It seems crazy to me that firebrick and refractory are so expensive in Australia - key component is alumina, and Australia is home of the worlds largest bauxite mining operations (and probably reserves too, I dunno). Sounds like a business opportunity!
                    My build progress
                    My WFO Journal on Facebook
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                    • #11
                      Everything in Australia is expensive. A can of coke will cost you $5. We have a decent minimum wage here, apprentices drive around in $65K light trucks and everyone wants to be a millionaire.
                      Kindled with zeal and fired with passion.

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                      • #12
                        Originally posted by fergo View Post
                        ok sounds like i might have to just keep my eye out for some cheaper firebricks and make it out of brick. thanks all
                        Here is a link to one cast oven here on FornoBravo.

                        I made a post about DIY Castable mix some time ago, here it is:

                        Originally posted by Lburou View Post

                        During a visit to my local refractory, I spoke with the owner and his engineer about a home made castable for my best friend working overseas where commercially prepackaged materials are not readily available. This is the home brew recipe they gave me -use at your own risk:
                        30% Ciment Fondu (calcium aluminate cement I'm sure you can get some)
                        60% Aggregate (#6 mesh -sizing 3mm down to powder)
                        5-10% Fine Sand
                        5-10% kyanite (crushed, Metamorphosed peri-aluminous sedimentary rock, optional, if not available locally-add more fine sand)
                        HTH
                        Last edited by Lburou; 12-08-2016, 09:50 PM.
                        Lee B.
                        DFW area, Texas, USA

                        If you are thinking about building a brick oven, my advice is Here.

                        I try to learn from my mistakes, and from yours when you give me a heads up.

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                        • #13
                          only cheap things in Australia are the politicians and their opinion

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                          • #14
                            Here is Sonomacast's cast oven thread...Very informative. HTH
                            Last edited by Lburou; 12-08-2016, 03:49 PM.
                            Lee B.
                            DFW area, Texas, USA

                            If you are thinking about building a brick oven, my advice is Here.

                            I try to learn from my mistakes, and from yours when you give me a heads up.

                            Comment


                            • #15
                              thanks for the links, very interesting reads

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