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Dome cracks

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  • Dome cracks

    We lit our first fire and found a tiny hairline crack on the
    claddign around the oven. Should I fix it? How, with Concrete or
    something more flexible?

    Aesthetic question...
    The bricks I got have cores in them which is fine for stacking but I
    am not sure how to finish of the top so that teh holes don't show.
    On the chimney, I will likely stand the last row on end but what
    about the front facade that doesn't go as high? Any suggestions?

  • #2
    The cracks are no doubt due to expansion and will expand and contract with
    each firing.
    As long as they are only hairline, no need to repair. Since they almost
    disappear when
    the cladding returns to room temperature. As long as the inside bricks have
    been properly
    mortared you shouldn't have any leaks that will be a cause for concern.
    If you see smoke coming out the cracks, this may actually be water from the
    concrete or
    mortar being vaporized because of the heat. This may have added to the cause
    of the cracks
    in the first place.
    Have several more firing before you insulate and close in the dome. Monitor
    the cracks to see
    if the continue to grow in width.



    • #3
      My vent area leaked smoke in 3-4 places on my first outdoor mailbox
      oven. I just let it fully dry out, then covered it with a second
      layer of refractory mortar. Then, as Jeff says, I made sure the whole
      assembly was smoke-tight before I moved on to insulation and my
      finish walls.

      Has anyone ever pointed their infrared thermometer at the vent
      masonry when the oven it hot (I don't have a gun here). If the oven
      floor is 700F +/-, how hot is the vent right about the oven opening?



      • #4
        It's not a problem. Wait until you've used it a half-dozen times. That
        will dry it all out and any cracking will be at max. Then fill it with
        furnace cement (you can get it in caulking tubes). Fire the oven after
        filling the crack(s) and keep filling in any expansion that occurs as
        it heats up. One of the advantages of the Pompeii design is that all
        of the brick front edges mate without mortar joints inside the oven
        which will keep it structually sound despite any cracking. (If you
        want you can make a V groove along the crack to open it up enough to
        get the cement into it.) Cracking is why you insulate with a fireproof
        material like vermiculite -- no chance of it catching fire.