Pizza Oven--Insulating with cob/adobe

Pizza Oven/Insulation added

Since far and away the most interest my art blog generates is for my home-made, adobe bread and pizza oven I thought I should reward all those random readers with an oven update.
As I said previously in my last Pizza Post, it is functional as it is now but would stay hot longer if it was better insulated. For a cob/adobe oven; insulation means: dirt/sand/clay mix but made into a slip by adding more water and then folding in hay or grass or sawdust. I had a big bag of woodshavings and sawdust from a neighbor's woodshop so that's what I used but I added some dried cut stemmy grass to give it a little more structural stablity.

Here is the process;
First I made some moist clay/soil mix and patched the few cracks that exist in the insulation layer I had built previously.

Then, I mixed up a wheelbarrow's worth of woodshavings/sawdust with clay/mud slip.
I mixed it with a shovel and then threw in a bucket of dried grass/stemmy clippings.
(Straw would have been better but I had a pile of cut grass).

Then I added about a two-inch layer, fistful at a time going around the base and then up the sides to meet a layer I had already added to the top. By slapping it on it didn't slump and the grassy bits helped meld the fistfuls together. I gently smoothed the surface and then added some scratches in the surface to help the next layer adhere/stick.
Now, I'll let it dry for a day or two and decide if I want to try to add a finish or smoother layer. It will take several days to dry out and I'll post again about how it works then.
But here is a photo of my last pizza: Potato and leek with garlic oil. It was tasty.

Wood fired Pizza

I promised all who were following my slow, intermittent mud/cob/adobe oven posts that I would post a photo once the oven was done and we made the first pizza.

Well, the oven isn't technically done; we did add a 2 1/2 inch layer of mud/woodshaving/sawdust insulation but it would really benefit from another layer of insulation and a finish plastering of mud/sand to help make it more weather resistant.


BUT, the working part; the clay shell and 1st layer of insulation is all you need to bake and like the impatient child that I am (and my kids were asking, when are you going to make pizza, Dad?") we lit up the fire.

I built a small starter fire and kept it going for 2 hours adding sticks of hardwood 3-4 times during that span. I made a sourdough dough the day before and used the leftover dough to make 3 10" pizzas. The oven worked great. The pizzas cooked in about 2-3 minutes and the bread cooked in 25 minutes (instead of the hour I usually need in my conventional oven at 450degrees F.) and the only problem was that my dough was too "sourdough" for a real Pizza margherita. Next time I'll mix up a bona fide pizza dough and make them a little thinner.

Pizza Oven taking form

Well, I haven't been printmaking much because my simple "2 weekend" project has stretched on and on.

Mostly my part for making it bigger than we probably need for a home "test" oven. It finished out at 27-28" in interior diameter which seems small but requires a lot of material. Last weekend we gathered sand from the beach and from a friend's creekbed (13 five-gallon buckets total) and I dug another 4 of mud/soil/dirt from the yard.
We built a little test dome of wet sand to see if it held, I made a few test bricks of my mud and when all looked good we charged ahead.

First day of round III: I got up early and layered a 1/2" layer of sand over the dense mud base. Then I carefully placed my firebrick hearth on the sand getting them tight together and all flat (I needed two tries).

Then I mixed a bit of mud to "mortar in place the brick floor of the opening. Then, once I got a few neighborhood kids together we built the sand hemisphere which serves as the form for the clay shell. It took a lot of sand and a lot longer than I imagined. 6 Buckets of sand later we had a nice smooth sand dome.

Day 2 of round III: Get a tarp. Put out 4 buckets of sand in a circle, 2 buckets of soil/clay in the middle, add a bit of water from the hose and mix. We mixed with our shoed/booted feet (some sharp stones in the sand). It took about an hour to mix up half of the mix for the shell. Jumping and grinding the sand into the clayey/dirt. We started building the clay shell packing it carefully around the dome of wet sand (which we had covered with wet newspaper to keep it separate from the mud.

We should have finished the dome the same day. But we were too slow and my helpers all abandoned me to play outside.

Day 3 of round III: We finished the clay shell once the kids got out of school. We built up and in and over the top of the dome trying to get 4 inches thick layer over the sand. We finished just before dark and I evened it all out with a wooden board.
Now it looked a bit like Jabba the Hut in Star Wars.

Day 4 of round III:
Now the hard part. I need to carefully scoop out the wet sand from the doorway and not have the clay oven collapse. I waited a bit too long and a big crack opened up as the walls of the dome slumped a bit over the rigid sand form. It closed once I dug out the sand and shouldn't be a problem. But it didn't collapse! Now, with the sand out it will dry faster.

While not finished (I need to add an insulating layer around the clay and smooth it all out so it looks nice) but it will be useable once it dries for pizza at least. Tomorrow we'll light a little fire in it to help dry out the clay.

No pizza tonight. From building the sand dome to finishing the clay shell should all have been done on the same day but it took us 4 days. It would go faster if I have to do it again but the real key is to get help and do it as a group project.

Pizza Oven

We've been gone from Italy now for 8 months and I miss the farm, the food and our house.
But I've been filling my time with some little projects and started to build an outdoor woodfired pizza and bread oven so I'll be able to make those thin crust pizzas and Tuscan bread.

It started when I dug a hole in the backyard to root out some invasive bamboo and found in one corner of the yard some pure white clay. That started me thinking about clay tiles....then adobe bricks....then I remembered seeing a book about earth ovens.

So work has begun. Since I couldn't decide on a permanent site and I wanted to build a smaller test oven to see if I really use it, I built a semi portable base using leftover 4X4's, 4X6's and 2X4's. I put it on casters (each rated to 350 lbs.) and built a top of leftover planks and plywood. On top of that went one layer of 12" X 12" Cement pavers. Next a ring of firebrick to enclose a layer of insulation. To keep the hot oven from eventually burning out the base I insulated the top with a mixture of subsoil and clay (the dirt that came out of my yard) that I mixed with water until I had a thick, clay-slip consistency.
I folded in half a bag of perlite (volcanic puffed rock from the building supply store ($14.00) to end up with a 4" thick layer of light insulation. It looks like and behaves like a mineral version of the RIce Krispy treat!

It's still wet but the next step will be to add a layer of dense clay/dirt over the insulation to act as a heat sink over which will go the hearth bricks and the real oven per se. I'll post more photographs as they happen.
No pizza tonight.

NOTE: Much of my information come from the book "Building your own Earth Oven" by Kiko Denzer and Hannah Field. I highly recommend it as it includes a wealth of information on ovens, building (on the cheap) with scavenged or recycled materials, has bread recipes and photos of lots of different ovens big and small for ideas.