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Trapped Water

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  • Trapped Water

    I've built a Pompei style oven - which over all went very well for a first timer. I think I've got a big problem though - wet hearth floor insulation. I laid FB board under my hearth as recommended (see photos), however due to very rainy summer and long periods of me gone and not adequate cover, the boards soaked up water and appeared saturated from the edges. No way to know how far in the saturation went, so I let it dry as long as I could, and then finished up the oven deck, top,etc. Now I've been curing and firing for the last three weeks. Two firings now and I've had a cold bottom. Baked 10 pizza's last night and pre-fired the oven for four hours and the oven chamber held 700F no problem. It draws well and holds heat well. BUT - way too much top heat and not enough bottom heat - tops browned and bottom still like a baby's - white and soggy.

    I have not yet used a direct read thermometer yet but I suspect that the wet floor insulation is preventing my hearth from getting to full temperature. And I'm also presuming that that moisture is all trapped in the sandwich between the slab and deck now and has no way to evacuate - it may be trapped there for a long time.

    Any ideas?? I was considering impact hammering the sides open and with a long ship auger angering that insulation out from under the cooking area and replacing it with metal pipes or something to support the hearth floor while letting the remaining insulation ventilate. Anybody who has a better idea I'd love to hear it! Thanks

    - Fred in Wisconsin

  • #2
    Fred, I had wet insulation board and it took me 6 or 7 long slow curing fires to finally drive all the moisture out. Fortunately I did it before I put the stucco over my insulation so I could see the flow of water and it was not impeded. Do you see any wet/damp spots in your outer cover around the periphery? If you do, you might be able to drill some small weep holes and do the slow curing fire thing.
    My build thread


    • #3
      The remedy is to just keep firing the thing, it will dry eventually. I like to shape the supporting slab with a slight hump in the middle to discourage water pooling under the insulation. Also one or two holes in the supporting slabso the steam can escape downwards will help. You can drill some from underneath.
      Kindled with zeal and fired with passion.


      • #4
        firebrick loves to soak up water. House bricks are build to repel water. Firebrick isn't. You have to modify you oven in such a way as to stop the rain from soaking into your insulation via the hearth bricks.
        regards Dave
        Measure twice
        Cut once
        Fit in position with largest hammer

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