New builder from Somerset.

[bellibhai]

 I've read a fair bit over the last week....lots of different ideas on a castable refractory formula. Lots just using Portland home-brew type mixes.

I'd really like to use up the cement and needles at the least. Does anyone see any problems with my recipe??

Hopefully I can cast a couple of inches and then insulate over the top.

Any help would be much appreciated.


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[scotsoven]

Bellibhai, I am no expert just finishing my cast dome I used the homebrew method 3-1-1-1 sand, fireclay, hydrated lime and cement didnt use SS needles but polypropylene fibres as recommended by downunderdave on this site. Have only had curing fires so far up to 350 deg C but had no cracks planing on going big tomorrow and cooking pizza🤞 best advice i was given was to use a sand mould to cast over again by dave, bit of a expert on casting, thanks dave for your advice👏Used the sand i was going to need for the rendering so no waste. My kid plays with the gym ball i bought in the garden but even after over inflating it is still soft could not imagine trying to cast over this now.

Was originally going down the gym ball and vermiculite route that i had read and seen videos on but after building the base thought i am going to try and do this right. The people on this forum are great and i wouldn't have got the same oven if not for their advice. Another tip i gained is insulation don't scrimp specially under the oven floor as it ain't easy to change. Best of luck with your build.

[downunderdave]

The addition of perlite or vermiculite to a castable mix drastically reduces strength. This is a problem as an oven is subject to abrasion and bumps when working it. In addition the perlite turns the mix into an insulating one so apart from strength it both reduces heat up time and the ability of the mix to store heat because of it’s lowered thermal mass. This does create difficulty in maintaining pizza temperatures and the ability of the oven to do retained heat cooking. It is also doubtful if stainless needles will compensate for the loss of strength to such an insulating castable. Polypropylene burnout fibres are a more important addition. I have not read, despite invitations, of the long term success of such an insulating mix using either CAC or Portland cement. I suspect failure in the long term.
Take a look at more builds both here and at Forno bravo before forging ahead with your current plan.

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