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Cracking mortar

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  • Cracking mortar

    Hi all I am at the 2nd course stage of my oven ,I have covered the outside of the bricks with a layer of mortar twice now but each time the layers crack and fall away. The first time I used a mix of 50\50 fire clay and sand which was then covered with tarpaulin ( was in Feb \ march ) second was with a pre mix of heat proof mortar which again has cracked. I don't want to progress any further until I get this sorted.
    Any ideas and help would be greatly appreciated.

  • #2
    Re: Cracking mortar

    Fireclay and sand is not mortar, it is mud. If your premixed refractory mortar came wet and ready to use, it has a design thickness of 1/8" or less, and is not suitable for use as a plaster (or for building a dome oven, period).

    For plastering the outside of the dome, normal pre-mixed mortar is fine, save the refractory mortar for laying the bricks.