Adobe Caliche as refractory

[Chfrob]

I live in Tucson in the desert, I built my first pizza oven and found that i didn't know what i was doing and that it was the worst cooking experience i have ever had but am not discouraged as i learn by failure (This can be an expensive way of learning!) So im tearing it down and starting over originally i just wanted a something to fill in the awkward rounded corner of my adobe wall Ive decided to build it closer to the house next to the chimney and brick firewall and not facing the afternoon full sun! I think that extra heat of the day along with the fire added to my horrible experience. I have saw a fun little add on in a few altered plans called a rocket oven to help preheat the oven, i also think a barrel vaulted style oven that is slightly altered to have a rounded backside might work better for the location Back ground I live in a geodesic dome house and have a fireplace but its not built into the chimney, the chimney is just for looks but it does vent the smoke from the fireplace inside which doesnt vent until about 7-8 ft up, i would like to build the barrel next to the chimney and vent it into the chimney, however i am wondering is i can cast the barrel/dome out of local caliche clay i do believe that this type of natural cement is a refractory does anybody have any experience with building an adobe pizza oven? i was planning on using the firebricks that i bought that are thin to line the oven and cast over it in the adobe mud. thoughts? ideas? would love to build it to match the house. but thats way to many cuts to make

[david s]

Definitely use the firebricks for the floor of the oven as they take the biggest beating and also perhaps around the mouth of the oven which is also subject to bumps and abrasion. The usual mix is 2 parts sand to 1 part mud (clay) by volume. If the clay content is too high you get excessive shrinkage and cracking as you've no doubt learnt from your adobe experience. Many years ago I built a small icosahedron house in the bush as well as teaching students how to build plastic straw and pin geodesic spheres, so have been a geodesic fan for a long time. When fired the clay will not sinter (become permanent). That only begins at 573C, but will become extremely hard/ The biggest problem is eliminating the water from it once built. Generally potters allow their wares to dry for a week before firing, but as their wares are nowhere near as thick as the walls of an oven you need to wait for a fair time before putting any fire near it. As an extra assistance for the water elimination, fine polypropylene fibres as used in concrete fibre reinforcing, should be added. These fibres melt at 160C and then leave a network of tiny pipes through which water can escape. This provides a measure of protection from steam spalling. Depending on the size of the oven it does require a bigger vent than you'd think, if you are going to make it as a cross draft system (flue gallery at the front). You don't want to fill your house with smoke. Generally a 36" diameter oven requires a 6' diameter (or equivalent cross section area) flue. An updraft system oven with the flue at the apex of the chamber (not quite as efficient, will work with a smaller area flue and you'll never have issues with smoke.

[UtahBeehiver]

I would also suggest you download the free eplans from Forno Bravo's website under "resources". It contains a good overview of oven design, performance and construction. Although primarily centered around dome style ovens it will give you a good basis. David S is our cast oven expert.