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Vermiculite+portland cement to make fire bricks? What is fire clay?

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  • #16
    Re: Vermiculite+portland cement to make fire bricks? What is fire clay?

    "Cracking is not an issue with the rocket stove. If it can be made with stacked bricks with their inherent spaces between then a crack in the chamber is nothing to worry about. Also, I am not sure that a clay chimney needs to be fired "properly" in a kiln since the example I saw was simply dried completely then heated using a wood fire. In this example the level of firing from the wood was adequate to harden the clay for its intended use as a fire chamber for a stove. Ideally though, if you have access to a kiln then you can be assured it was done professionally. However, for the cost of raw materials involved I'd go with doing it yourself. You can even fire clay the old fashioned way by putting the piece in a fire pit."

    Bob,
    Clay which is unfired can turn back into mud if it gets wet. it needs to be fired to 573 C before it becomes permanent and you'll never get it that hot in the chimney alone. You can try doing it yourself in a campfire or sawdust kiln, but it is tricky and prone to blowing and cracks as well as being not fired particularly high enough (typically a sawdust firing will be in the region of 600C) to make it sufficiently hard and durable. Should be taken to over 1000C IMO This would require a kiln. Using a castable means you don't have to fire it, although ideally even a castable is better if it is fired first.

    Dave
    Last edited by david s; 08-05-2011, 04:16 PM.
    Kindled with zeal and fired with passion.

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    • #17
      Re: Vermiculite+portland cement to make fire bricks? What is fire clay?

      Hi David s,

      Thanks for the clarification. Yeah, that sounds reasonable. Whatever works by experience is often successful enough. I agree, castable is the way to go. The other options will work too if you are mindful of their individual requirements.

      I like the part about turning back into mud if it gets wet. Lesson learned the hard way.

      Cheers,
      Bob

      Here is the link to my oven number 1 construction photos!

      Here is the link to my oven number 2 construction photos!

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      • #18
        Re: Vermiculite+portland cement to make fire bricks? What is fire clay?

        Hi guys, am new here. Am sort of an expert when it comes to what you guys call rocket stoves.
        A simple explanation on how to make a rocket stove is to use a steel cylinder of light gauge with a fire door at the very bottom and a chimney near the top on the opposite side of the door, on the side. The cooking pot should fit loosely inside the cylinder (leaving enough space for hot gases and smoke to flow) but completely cover the top (so that smoke will travel out through the chimney on the side).
        Now to come to your dilemma - insulation. The inner part of the cylinder is lined with a wall of clay bricks to give it strength to hold the weight of the pot. For insulation we use vermiculite mixed with terrazzo chips, a little clay and refractory cement.
        We call these types of stoves "energy saving stoves". No wires or nails are necessary. Contact me for a simple drawing of such a stove and pictures.

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