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Recently completed Pompei 36" oven: Hearth NOT HOT!

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  • Recently completed Pompei 36" oven: Hearth NOT HOT!

    I recently finished the construction of my third pizza oven ? a 36? diameter all-brick FornoBravo Pompei design. My first oven was constructed about 13 years ago ? a half barrel design following the Alan Scott Bread Book; then 5 years ago a 42? FornoBravo Pompei oven. I keep moving around ? and building ovens wherever I go. I love building ovens and making pizza

    I built this 36? oven using best quality materials ? high quality firebricks, hightemp mortar, 2 inch ceramic board insulation under the hearth and ceramic blanket insulation on top of the dome (procured directly from FornoBravo). Laid a mortar-less hearth using full thickness firebricks in herringbone pattern.

    I constructed in West Virginia during the months of October and November. Definitely a fairly rainy period. I did not attempt to protect the oven from rain.

    The oven cured for about 6 weeks without any firing. Kids came home from college for Christmas holidays and we all looked forward to making pizza in our new oven on Christmas Day. I made a small fire for 3-4 hours the day before Christmas so I wasn?t fully firing the oven for the first time on Christmas.

    Then on Christmas, I fired the oven for about 8 hours ? longer than I had planned ? we just got busy with fun activities. Spread the coals over the hearth about 45 minutes before cooking. Ready to bake ? I moved the fire to the side, brushing the hearth with a wire brush (no swabbing with wet sponge). Then measured the surface temperatures with my infrared thermometer: 350F in the center of the hearth and 720F on the back wall of the dome. I fired my oven in the same manner I have done with my previous ovens ? which would typically yield a hearth temp of 750-800F. I actually thought my thermometer might be broken. I threw a handful of cornmeal onto the hearth. Nothing. No browning. We tried to cook a pizza. The top browned and the underside was basically raw after 5 minutes. Typically that first pizza cooks in under a minute. So we decide to re-fire. I made a super-hot fire blowing on the coals with a hollow pipe. 90 minutes later we measured the temps: 500F in the center of the hearth, 850F on the back wall of the dome. Cooking pizza was still a frustration. No crispy crust. Just burning the top of the pizza.

    So, I read a post from 2010 where someone described a similar problem and others suggested the hearth insulation may be wet.

    My questions:
    --Is that the best explanation here? The edges of my hearth insulation were definitely exposed to moisture during construction. I just never imagined that it would wick moisture deep under the hearth.

    --Do I have any hope of drying this out with multiple firings (one guy posted that he had a problem heating his hearth for three years)? Don?t know how that moisture can get out, though?

    --Should I just bite the bullet and rip out my hearth and replace the hearth insulation. That sounds like a pretty difficult (but not impossible job). The 36 inch diameter dome would be pretty cramped to work inside of ? and that insulation board is so soft?.

    I?m very very frustrated and sad. So much time and money. So much expecation.

    Advice please.

    Thanks so much.


  • #2
    It does sound like it is still wet. I would just keep firing it. It should get better with each use. What type of rendor do you have over the dome insulation? And, how are you protecting the edges of the floor insulation? It will be crucial to keep any future water from getting in it.
    Joe Watson " A year from now, you will wish that you had started today" My Build Album / My Build


    • #3
      It sounds to me like you have done only the most cursory of curing processes. Air-dry for six weeks and a single 3-4 hour firing is just not enough to cure an oven. There are plenty of threads on curing approaches - but most of us go through a series of fires for a week or more. So I would, as Gulf suggests, light a few more fires!

      If you're really concerned about the insulation being wet, you could pull up a few of your oven floor bricks to check moisture content. It's not too hard to get them back in place. If the insulation has soaked up a lot of water (which it likely did if exposed to the elements during construction) then removing most of the bricks and putting a space heater in the oven for a few days should dry it out.

      Good luck!

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      • #4
        Thanks for the thoughts:
        1. Re the rendering over the dome. I have put two coats of stucco over the dome insulation. It goes down over the outside edge of the of the hearth insulation - so I don't think there is any way water can get into the hearth insulation at this point. We would like to do a third cosmetic layer - perhaps a stone facade, but haven't decided yet.
        2. Re curing. OK. I hear you. Will do a week of fires and then take some measurements of hearth temp. I like the idea of checking under one or two bricks and using a space heater (in contrast to ripping out the insulation board)!! Nice idea. Thanks so much.


        • #5
          Listen to Deejay and Gulf they know there stuff. Oh and happy new year guys . Go see my thread I cured/tempered [the 2 are different] my oven for nearly 3 months.
          Cheers Colin

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