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cracks - Forno Bravo Forum: The Wood-Fired Oven Community

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I'm Peter Reinhart! Ask Me Anything! Monday, February 15, 2016 7:00-8:00 pm EST

To kick off our AMA feature, we have invited author, chef and master bread maker and host of Pizza Quest, Peter Reinhart, to be our first host! Peter will be in the Forum on Monday, February 15th, from 7:00 - 8:00 pm EST. If you are unable to be online during the live session, you can post your questions in the sticky post. Peter will answer those questions during the live session on February 15th. You can view Peter's answers to your questions as well as what happened during the live session in the session thread.

Ask Me Anything New Forum Feature

You will notice a new forum at the top of the main page called, "Ask Me Anything". This forum will be used for live one hour "Ask Me Anything" (AMA) sessions hosted by people who are knowledgeable in different areas pertaining to wood fired ovens. How it works:
- Each AMA will have a "sticky" thread where the community can post questions they would like answered during the live session. This will allow everyone to participate even if you can't be online for the live session. These questions will not be answered by the host until the live AMA; if you need an answer quickly, you should post it in the appropriate Forum area for the community to respond.
- Another thread will be posted for the live AMA. Registered users who are logged in during the live session can interact with the host by asking questions and receiving responses.
- The live thread will remain in the AMA forum to view after the session.

We hope you enjoy this new feature! Please let us know if there is a topic that you'd like to have as an AMA and we'll look for a host!

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  • cracks

    hello em here from australia i have just finnished building a 50 inch pompeii oven and am very happy with the finnished product. however i did not use a fire blanked but used 4 inches of vermiculite concrete then chicken wire and and more than 1 1/2 inches of concrete.i left oven to cure for about 2 weeks and then followed the 5 step curing fires as recomended in forno bravo plans . however the out side of my dome has cracked quite badly but the inside brick are perfect.i would like to rerender my dome and am thinking of useing a slip layer any advice for me and how to render a slip layer. thanks em

  • #2
    Re: cracks

    "the inside brick are perfect"

    This is what counts. Cracks on the outside of the dome are common.

    At one time it was advised to have several layers of heavy duty aluminum foil as a slip layer, although this practice seem to have fallen out of favor.

    Comment


    • #3
      Re: cracks

      thanks neil i am thinking just to rerender over dome with plenty more chicken wire once it has fully dried out there is still plenty of water in the vemiculite

      Comment


      • #4
        Re: cracks

        Hi Em,
        Because you used vermicrete for your insulation you will have added hundreds of litres of water in the application of this layer (around a third of the volume of vermiculite that you used) To evaporate this much water you need way more than a couple of weeks. Ask yourself how long it would take to boil dry a 44 gallon drum of water. The cracks have occurred because water present in the insulation layer has created steam pressure. Don't be in a hurry to render over the cracks until you are 100% sure the water has been removed.This usually takes about 10 decent firings after the initial curing. If you apply some kind of slip layer, you are also sealing in some of that moisture. I foiled over my vermiculite layer prior to rendering the outside shell. In two places I punctured the foil with quite a few holes and it is in these spots that the oven gets hot on the outside after rainy periods, which is an indication that the vermicrete layer has moisture and steam is finding its way out there.This is a handy indication of what is going on inside but I wouldn't do it again. It slows the drying process too much.
        Dave
        Kindled with zeal and fired with passion.

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        • #5
          Re: cracks

          thanks david. yes i agree totaly with you the other thing i did was to render with concrete two days after i rendered the vemiculite, in the middle of winter.traped all the water in .i think i will render over it in a few mouths time by then should have used it over 10 times regards em

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          • #6
            Re: cracks

            Yeah, don't stress over it.The outer shell is only to keep out the weather. But should it rain it would be best to cover it because the rain will enter through the cracks.
            Kindled with zeal and fired with passion.

            Comment


            • #7
              Re: cracks

              I also put a vent in the top of the dome thru the stucco and into the vermicrete layer. This is a 1 in dia vent with a rain cap. I also have four 1 inch vents around the perimeter at the bottom of the insulation layer. During firing after a wet spring, I often see steam coming from the top vent.

              Comment


              • #8
                Re: cracks

                Originally posted by Neil2 View Post
                I also put a vent in the top of the dome thru the stucco and into the vermicrete layer. This is a 1 in dia vent with a rain cap. I also have four 1 inch vents around the perimeter at the bottom of the insulation layer. During firing after a wet spring, I often see steam coming from the top vent.
                This is a good idea Neil, I've also incorporated a vent into the insulation space via a system that also supports the flue pipe
                Kindled with zeal and fired with passion.

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                • #9
                  Re: cracks

                  venting the insulation intresting, but here where i live we only get 13 inches of rain per year here

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                  • #10
                    Re: cracks

                    In our wet season we might get that much in one week.
                    Kindled with zeal and fired with passion.

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