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Brick porosity - Forno Bravo Forum: The Wood-Fired Oven Community

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Brick porosity

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  • Brick porosity

    I did a test of the brick porosity of one of my firebricks yesterday. The brick was 12"x 9 1/4" x 3" and weighed 9.25Kg dry. Soaked for 24Hrs it weighed 11.5 Kg which is approx.20% I did not remove moisture from the dry brick first and my old spring bathroom scales are not too accurate but it indicates that the brick has taken on a lot of water. This indicates that the brick is very porous and not very vitrified. This quality is desirable to make the brick highly refractory but undesirable in that it will absorb water easily and hold a large quantity. I have read that it is the moist heat that is the WFO's secret, so perhaps the porosity of the bricks is an important factor in the WFO's success in cooking superiority.
    Kindled with zeal and fired with passion.

  • #2
    Re: Brick porosity

    Slow day at work was it?
    The English language was invented by people who couldnt spell.

    My Build.

    Books.

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    • #3
      Re: Brick porosity

      No, flat out actually, but it is a topic I've been getting interested in and was hoping someone else might might chime in to give some constructive input into the subject so we can all benefit from increased knowledge. And weighing one brick is way easier than cutting lots of them.
      Last edited by david s; 05-17-2011, 01:51 AM.
      Kindled with zeal and fired with passion.

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      • #4
        Re: Brick porosity

        Originally posted by david s View Post
        And weighing one brick is way easier than cutting lots of them.
        Why are you cutting lots of wet bricks?
        The English language was invented by people who couldnt spell.

        My Build.

        Books.

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        • #5
          Re: Brick porosity

          I didn't say I was.
          Kindled with zeal and fired with passion.

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          • #6
            Re: Brick porosity

            I agree, but is it the fuel used or the porous bricks that give it that superiority?
            I think also that a WFO cooks with radiating heat rathe than by convection like a standard oven.
            Maybe someone with experience with both a steel dome and a firebrick dome may chime in. Although a steel dome with a firebrick floor is still half a firebrick oven.
            Kindled with zeal and fired with passion.

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            • #7
              Re: Brick porosity

              The ones we carry give a rated porosity of 13-17%.

              http://www.wgpaver.com/files/PDF/Fir...heet%20Red.pdf

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              • #8
                Re: Brick porosity

                Thanks Tscarborough,
                Given the high degree of porosity of fire brick, presumably some containment of water, rather than full saturation, in the brick when laying them is desirable to reduce the tendency of the brick to suck water out of the mortar too fast. Is this a logical conclusion?
                Kindled with zeal and fired with passion.

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                • #9
                  Re: Brick porosity

                  Yes, as I have stated a dozen times, the proper amount of water is SSD. Saturated, surface dry. That is to say, the surface will not have a sheen, but it will be damp. Usually, a dip before use is adequate, but in hot (like yours and mine hot, 95+ degrees) and windy, you may have to either soak them and then allow them to dry a bit before use, or, as recommended by the BIA, hose the pile every now and then.

                  As an FYI most common brick have less than 5% absorbtion, and hard fired face brick are usually far less than 2% in a 24 hour soak test.

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                  • #10
                    Re: Brick porosity

                    As an FYI most common brick have less than 5% absorbtion, and hard fired face brick are usually far less than 2% in a 24 hour soak test.[/QUOTE]

                    I wonder then if this would explain why firebricks are considered the superior cooking brick, with more porosity and their ability to store more moisture, are the preferred choice over common reds?
                    Or is it their greater ability to withstand thermal shock?
                    Or doesn't the difference really matter?
                    Kindled with zeal and fired with passion.

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