Home brew oven questions

[Slayt]

Hi all, started building an oven at the start of the year, just recently got around to doing some more of it, dome will be 6cm thick with ss needles on a firebrick base sitting on 40mm of Calsil board,

i poured the dome last week it turned out ok, but there are a few voids around a cm wide and some ripples were the paper got bunched up, is it too late to fill these,Im not really worried about them but maybe the bigger voids I should fill

the dome is fairly moist as I’ve been curing it under a towel and tarp,

for dome insulation I plan on using 2 layers of ceramic blanket will I need a perlcrete layer as I would prefer to leave it off as space is an issue

also what sort of curing schedule is suggested for a home brew casting, ie how long before heat is applied

look forward to your response and t(ants in advance

[UtahBeehiver]

David S from Queensland is our forum expert on cast ovens as far as if you can repair or fill the gaps on the inside. I can comment on a couple items. Even though a cast oven, it is still heavy, some diagonal cross bracing should be considered. I cannot tell from the pic, but if this is CaSi board directly beneath the oven, then some means of protecting water from getting to it and soaking it is important. We CaSi is one of the main reasons ovens perform poorly. Also what is under the CaSi for support? You do not need to put on a pcrete layer if space is a premium, but you will need a render layer or two to smooth out the irregularities of the ceramic blanket. You can use the curing fire schedule located on the Forno Bravo website as a good baseline. Current thoughts on the forum is to let the casting dry well, then insulate, cure (SLOWLY), then render.

[Slayt]

Bricks are siting on calsil board which is on a sheet of thin sheet of fibre cement board under which has 90 x 45mm kd hardwood at 450mm centres, I’ve been thinking about the waterproofing stage and am considering painting a waterproof membrane over the board and laying a tile screed over that and than tiling to finish it off, or maybe just waterprofing than a polished concrete layer over that

[david s]

You will get a better bond if the casting is still moist. Try to scratch out any newspaper stuck in the voids then apply a thin slurry of cement and water to the voids 5 mins before filling them with the homebrew mix. Force this mix hard into the voids.Recover the casting for another week to help the damp curing of the patched bits.
The vermicrete layer over the blanket does two things. Firstly it provides a firm substrate to render against and secondly it evens out the lumpiness of the blanket. This allows you to make the thickness of outer render layer thinner and more consistent. You can render straight against the blanket but it is more difficult because it’s a bit springy.

[Slayt]

Ok so I can start firing after around a week?, if I do use a perlcrete layer what is the minimum thickness?,