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Help! Bad dome inside

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  • Help! Bad dome inside

    So I finally moved the oven dome to take a good look inside, and it's much worse than I anticipated

    I'm hoping I can fix this by grinding out the layers that had slid down the lower layers.. Or potentially adding a coating to extend the layers that had slid down so they go all the way down the dome. Not sure if the castable will bond well at all.

    Any ideas guys?

  • #2
    The appearance on the inside is really only cosmetic, so a vigorous wire brushing followed by filling any larger voids with a peanut butter consistency of the same material you used for the casting and forcing it in hard may work ok. This operation has to be done when the casting is still moist. As you said “finally moved”, that would suggest that the casting is now pretty dry. You may have to re wet it, but be careful because it won’t work if it’s too wet either, it needs to be somewhere between wet and dry. It also helps if you sieve out the coarse aggregate from the mix which gives you a richer brew that is easier to work into the finer voids. You don’t say what type of material you used, homebrew or proprietary castable. This can make a difference because they use different types of cement which have different curing requirements.
    Kindled with zeal and fired with passion.


    • #3
      I was thinking using an electric grinder, would this be too forceful and potentially cause further cracking? A wire brush may not be hard enough to get rid of the excess layering though, but I'll give it a go.

      I'm using something called Cast 13ES - Extra Strength Fireclay Castable from a refrectory company. It has a chemical composition of Alumina (36%), Silica (50%), Iron Oxide (1.5%) , and Lime (9.5%).

      The dome has had a long time to dry, around 2 weeks.

      I used glad wrap as a layer to protect the form but it has backfired on me because there are a few small pieces stuck in the dome; would these eventually burn out, or is it probably better to remove through through wire brushing too?


      • #4
        The data for your product says it contains aggregate up to 5mm. That is relatively coarse for a castable refractory, so if it were mine i would be sieving out anything bigger than 0.5 mm and rewetting the casting as previously explained as it has been drying for a couple of weeks. You have a castable that contains calcium aluminate cement which cures and reaches max strength in 24 hrs so no need to damp cure again. You just do not want the dry casting sucking the water away from any new stuff applied to it.
        Any glad wrap stuck in the casting will burn away, although burning plastic is not too healthy so get rid of as much of it as you can.
        Last edited by david s; 11-22-2018, 01:22 AM.
        Kindled with zeal and fired with passion.