Luis Molero

Marco Banks wrote:Adding fire clay to any standard mortar will significantly enhance its capacity to handle heat.  

As for adding insulation, cob itself is something of an insulator, you just need to make it quite thick.  My cob oven is at least 8 inches thick, and thicker in some places.  On top of that, there's an inch of plaster to seal it.  All that mass heats up and then retains heat for a long, long time.  I used a high percentage of straw and sand in my mix, and the oven hasn't cracked.  I've heated it up REALLY hot and kept the temp super hot for 48 hours to fire the oven.  It got so hot that it charred the wood skirt around the outside of the oven and bubbled the paint on the boards, but the clay itself is fired rock hard.  

That sounds really nice, your oven have bricks in the inner part of the dome? Could you tell me the proportions you used for your cob? It would be great if you post a picture!

Chris Sturgeon wrote:If you can tight pack the bricks in such a way that the mortar is minimally (almost not at all) exposed to the inside of the oven, I would use a clay and sand mixture. Research 'making cob' for instruction on how to mix it.

What do you think about this recipe from the "forno bravo" guide:

•1 part Portland cement
•3 parts sand
•1 part lime
•1 part fireclay (i will try to get the clay use to make the bricks of the pictures)

"Still, fireclay mortar is less heat resilient and thermally
conductive than a true refractory mortar"

Rob Lineberger wrote:You can definitely use rice hulls mixed into cob as an insulation.  Its a great insulator in fact. Cob is basically clay dirt and sand.  

Do you think that i can put on top of that cob regular concrete so it has a nicer look and it is more resistant to the weather? In this way the dome will consist of 3 layers, the bricks, the cob with the rice husks, and the concrete.

Now that i am reading the "forno bravo" guide i think a can make the mixture for the binding of the bricks with portland cement, fire clay (i will try to get the clay they use for the bricks i found), lime and sand.

Doing that with the bricks the cob with the husks would only serve the purpose of insulation

Rob Lineberger wrote:I think that would make a great oven!  I'm jealous of your find.

Ohh dude, those words really give me fate, it has been hard for me to find ways to make my pizza oven happen ;(

I was happy thinking that fiber glass would work as insulation, but that isn't the case... I can get fiber glass, but no ceramic fiber...

What about using rice husk instead of perlite in the recipe that you send me? Or on the recipes that you know that use perlite?

these bricks are the best ones i can find where i live (venezuela), are they fine? (we call then rustic bricks). and i can´t find here any refractory cement or somethig like that, what could i use to bind the bricks? regular cement mixed with something else?

Rob Lineberger wrote:There are plans on the site for building the base out of cinder blocks.

Cinder blocks wouldn't crack? My doubts are about the flat part of the dome, where you put the pizzas, my english is not that good i don't know if maybe you didn't understand me haha, or maybe you are saying that i should build the inner flat part of the dome like: 1.cinder block (down) 2.fiber glass (middle) 3.bricks (top)

My original plans where to put the brick dome on top of a cinder block structure (the cinder blocks not getting any of the heat)

Rob Lineberger wrote:Luis, I suggest you visit the Forno Bravo forum.  It is the gold standard for building brick ovens.  There are plans on the site for building the base out of cinder blocks.  They are not very big on natural building methods such as cob, but there are a decent number of cob builds in the forum.  I know you are using brick though, which is why I recommend you read that site.  I don't want you to do all that effort and have your oven crack or collapse and you be disappointed.  Masonry is quite heavy.

Also no, I do not think concrete is going to be sufficient.

Good reading and good luck!

Thank you i will check it out!

Hello everyone! I want to make a medium size brick pizza oven, i can't find perlite or vermiculite, because i live in venezuela, but i know where to get fiber glass wool  insulation for a goop price. I don't know how to make the base of the dome, should i do it like (from bottom to the top): 1.concrete,  2.fiber glass, 3.bricks?

Also, i can only get cement and maybe pottery clay, could you help me with the proportions of the mixture (including water) for the binding of the bricks? And also the proportions for the mixture that goes on top of the insulation of the dome (outside part).

i have sand and i can cosider using cob.

Anothe question, can i bind the bricks only with regular concrete?

P.s: where i live i can't get refractory cement

Thank you all for the help!! I might be able to find the fiber glass P.s: i'm new to the forum and i don't know how to make quotes, sorry...

Hello there! I'm making plans to build a medium/small brick pizza oven, maybe the inner diameter of the dome little bit bigger than the diameter of a yoga ball. i live in venezuela so it's really hard for me to find perlite, vermiculite, or fiber glass wool for the insulation layer, can i use a mixture of sawdust and cement or something like that for the outside layer? Or what could i use in wich proportions?

Or is it even a need for that kind of insulation in the oven i want to build? I would be using it to bake pizzas like once a week, for myself, or for no more than 6 people. It wouldn't be fine just the brick layer with an extra layer of concrete?