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wotavidone 05-31-2011 02:30 AM

Good day from South Oz
Hi, my name

cobblerdave 06-03-2011 11:41 PM

Re: Good day from South Oz
the pot idea sound interesting but the idea of an 8 inch 200 mm door doesn't same with the 26 in oven hearth. I built a forno brick dome 42 inch which is great plenty of room for pizza and dishes to fit through the door. ive seen the oven at bunnings and it looked a little 'dinky' to small for both a fire and a pizza. Try for something about 32 to 36 inches maybe. sorry not a home at the moment uther would figure out the door size for these and yes consider a sqaure door shape you can fit bigger dishes in.
Hebel can be an exceptable base insulation but being cement will break down over time in higher temps think of protecting it from heat with fb board or pealite layer on top. Yes I have Hebel as heath insulation in my oven no probs to date
The thinnes of the pot will not give you a good enough amount of thermal; mass to an oven. Pherrhaps use the pot as a base for covering of 1/2 brick commons and home brew heat mortar.
Again insulate the dome you got the mass you need now to keep the heat from escaping insulate the cheapest is probaly pearlite cement. dont be tempted to use house insulation unless you protect it from the hot bricks first so you may as well just use pealite
keep up a progresss report
this sound interesting sorry don't no much about pots

regards cobblerdave

nissanneill 06-04-2011 03:26 AM

Re: Good day from South Oz
Hi Mick,
Read Russell Javons' book, "Your brick oven, building it & baking in it",
ISBN 1 904943 25 X.
He has build numerous brick ovens and uses 2 of them commercially in his wood fired oven pizza restaurant down at Willunga. He uses only common red bricks for the dome and 2 layers orn2" fired clay pavers for the hearth,msee for an indepth look:



cobblerdave 06-04-2011 04:18 PM

Re: Good day from South Oz
Dear Mick
Sorry about the quality of that last post, did it on an I Phone waiting around a hospital...don't worry everythings alright and It gave me something to do.

Pearlite... is like syrofoam beads light and full of air exept there volcanic rock
the cement is only used to hold them together till there covered by someother layer. So when the cement burns away it doesn't matter. Yes my oven has a Hebel layer under the hearth but if you go this way at least give it protection of a layer of pearlite on top

That pot price is a bit hexy you could buy a lot of brick commons for that. Cutting the hole would be a little nerve racking. If you find youself using one first experiment on a small cheap pot first. A square entrance would be better ..straight unfancy cuts. Mark out the entrance on the pot then drill largist hole in the corners ( not a hammerdrill ). Then use an angle grinder to cut up to the holes Not past them. the round corners will make it less likely to crack.

Why increase your thermal mass with fire proof cement? Why not use clay on the outside. The pots clay as well so less chance of cracking due to 2 different materials reacting differntly with heat. Checkout the local road cuttings when you see a layer that is below the topsoil take some home smash it down with a hammer soak overnight. Roll in into a finger size piece and bend it backwards over itself over your finger. if it breaks straight good . If it bends most of the way and doesn't break great you found the right stuff. No I havent built an oven of clay I have made bricks for a house from it though. The mass of the oven can still be covered in pearlite and finally cement rendered to protect from the elements.

Its a great idea your making a steel stand as any failures can be scapped off and buried in the garden away from the brides prying eyes...

Regards Dave

cobblerdave 06-04-2011 04:49 PM

Re: Good day from South Oz
Dear Mick

Going brick great! whats with SA and pavers? Go commons (not House bricks full of holes)
If you havn't got a set of formo plans go to the forno shop and download a set for FREE. its all in there the bloody things massive and its all in there bricks, Mortar mixes, the lot

regards dave:D

david s 06-04-2011 07:59 PM

Re: Good day from South Oz
hi Mick,
If you use clay to clad the terra-cotta dome it will crack as it dries and shrinks, which is not a major problem because it is just adding thermal mass not strength. I think you would be better to use standard concrete 3:1:1 agg. sand, cement with half the quantity of cement replaced with lime. This can be reinforced with fibres, but do't use the plastic ones, they'll melt. Also don't use normal fiberglass as it reacts with the cement. You need a special alkaline resistant fiberglass for concrete.If the cement in this layer fails then the lime takes over just like the poor mans mortar.
I agree with everything else you posted. but I can't see drilling a hole through that ceramic pot without using a hammer drill, you'll be there for three weeks. An angle grinder with a diamond blade is my first choice.

david s 06-04-2011 08:19 PM

Re: Good day from South Oz
"An observation I've made on my own, which I have not directly come across yet while reading the forum - fire bricks while not doubt being more robust than clay pavers, are nowhere near as heavy size for size - at least not the ones I've been handling "

Maybe you are looking at insulating firebricks which are full of air and way lighter than a solid red. My firebricks are a little less dense than a solid red,because they are less vitrified, but you have to measure their density to tell. Insulating firebricks are not what you need for the inner parts of the oven.

david s 06-04-2011 11:37 PM

Re: Good day from South Oz
The materials used for dense and insulating firebricks are the same, but sawdust is mixed with the clay for the insulating bricks. The sawdust burns away leaving lots of good insulating air pockets. This fairly dramatically reduces the strength of the brick

cobblerdave 06-05-2011 12:41 AM

Re: Good day from South Oz
Dear Mick
The ideas are running thick and fast now. I just want to revisite a point that made earlier by DavidS it doesn't matter if the thermal mass layer cracks at all because it has your pot supporting it and that pot basically a dome. And if that cracks its still strong because the weight of itself and any other thing on it keeps it together. A dome is basically self supporting. Most ovens have a crack in them anyway but don't fall down and still cook the same.
Pearlite you can get it from hydroponic suppliers check the web and get some sent to you. The stuff full of air so it weighs nothing.... think of a bean bag full of strofoam beds and you'll get the picture. The local bloke sells a 100 Ltr bag for $36. ( a ltr is 10cm2) so you got about 1m2 to play with.
Interesting mix with the lime replacing 1/2 the cement.. they used lime in old brick chimneys cause it don't burn away like portland cement. Id use this myself and chicken wire as the remaining cement content will prevent the wire from rusting.
If its pavers you got its pavers you use dont worry about the round corners they will fill up with ash anyway I would recommend however lay them in a herringbone pattern so you oven tools don't catch on any stray edge.
With drilling holes in clay pots I should have explained myself better. I have drilled more drainage holes in most of the pots we have as they only come with 1 in the middle I use a masonary drill not in the hammer mode though other wise they break. Yep I'm afraid it slow... but safe

Regards Dave

david s 06-05-2011 02:29 AM

Re: Good day from South Oz
Lime in the outside render/stucco for an igloo style is also good because it has some elasticity, which is helpful with the heat wanting to expand things. I use a 4:1:1 sand, cement, lime mix about 15mm thick.

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