My "Earthy" Outdoor Kitchen Build Other Oven Types Discuss My "Earthy" Outdoor Kitchen Build in the Pizza Oven Design and Installation forums; When I first started this project, I was planning on building the dome out of clay that I had dug ...

[charger10s]

When I first started this project, I was planning on building the dome out of clay that I had dug up in my yard. After reading through the plans and many build threads, my original plan became a little in doubt. However, I eventually reached the point of no return and had to make a choice. Well, we decided to go with the original clay mixture, and we built the dome a few Saturdays ago.

I filled the hearth floor with sand and some bricks (for volume) and carved it into a dome, then covered it with wet newspaper.

We mixed the clay on a tarp using our hands and feet, as well as rolling it around by lifting the edges of the tarp. Then we had an assembly line going, my wife making the loaves and I was placing them on my sand form. Of course my daughter, once we could finally get her to touch the mud, also helped to make and deliver her own little loaves. She’s not used to playing in the mud, so she was very hesitant at first, it was so funny.

It was quite fun, but it was hard work. The clay here in AZ is pure clay, with little to no sand in it, so I had to add lots of sand to get the mix right. My original batch started with 4 shovels of sand to 1 shovel of clay. After mixing for a while, I eventually added more sand and more clay; so I would say my final mix was probably 70% sand to 30% clay, with just enough water to make a semi-solid loaf shape.

The drop test is a very effective way to check your mix; make a ball of mix (well patted and formed) and drop it from about shoulder height. Too dry and it will break into chunks, too wet and it will splatter. It will probably crack, but it should hold together.

[charger10s]

I sent James a PM, but if any of the Mods see this first, please feel free to move this thread to the Other Oven topic forum, as I am no longer a "Brick Oven" build.

We're moved....thanks!!

[charger10s]

I thought I would break this up a bit, but we did complete the first layer of the dome that same day. I started placing the loaves on the soldier course and worked my way around and up. I read several different articles about this method and most of them built the entire dome with no door and later cut the dome out after the clay had dried a bit. Well, I thought I would be smarter and build a wooden door form and place the clay directly on it.

It worked out fine during the building, but this technique has caused me some headaches, which I'll show you in the next post.

[charger10s]

I kept it covered with wet towels for a few weeks, so it would dry out nice and slowly, which is quite a challenge in Arizona in June.

I did have 2 or 3 pretty decent cracks on the top and a pretty significant crack developed about 4 inched above the door form.

I took out the door form and that chunk of clay above it did fall down, but the rest of the dome is solid.

I should have moved the door around while the clay was still moist, that might have helped to prevent the cracking and failure of that section. But, probably the best way is to build the full dome and cut the door after it dries.

So, no biggie, I will patch up that hole when I build my chimney and vent entry...still working out the final design for that effort.

So what do you think so far?

[dmun]

If I remember from my pottery days, clay shrinks ferociously from the wet stage to the "green" (unfired dry ware) That may be why you had a problem with your form. I would have guessed that since the clay shrunk and the sand didn't compress, you would have got cracks just from that.

Some folks who tried to make one of my geodesic ovens from clay had a collapse, but mostly I think because they didn't let it dry enough.

I'm interested in the seventy/thirty sand/clay proportion. In my ignorance I would have guessed that that wasn't nearly enough clay to hold together.

[charger10s]

Originally Posted by dmun

If I remember from my pottery days, clay shrinks ferociously from the wet stage to the "green" (unfired dry ware) That may be why you had a problem with your form. I would have guessed that since the clay shrunk and the sand didn't compress, you would have got cracks just from that.
.........
I'm interested in the seventy/thirty sand/clay proportion. In my ignorance I would have guessed that that wasn't nearly enough clay to hold together.

The extreme shrinkage of the clay is why you need the sand in the mix. The proportions tend to vary (depending on who you ask), but everything I've seen has been in the 60/40 to 75/25 range.

Like I mentioned, I think I came out around 70/30, and I had doubts because it did feel very sandy. However, the guide I was following actually mentioned that it should feel sandy, so I went with it, and it seems to be good so far.

We're going to do the second layer and build the entry, vent, and chimney this weekend. I'm hoping for my first fire on the weekend of the 18th!

By the way dmun, your geodesic dome is awesome!

[charger10s]

Here's a shot of the inside of the dome, just prior to the construction of the entry and vent to chimney. The newspaper you see was put on top of the sand form to keep it from sticking to the clay. It will burn off in the early fires.

I've also put a pic of the mockup of the vent and chimney prior to filling in the sand for the form.

[charger10s]

I had to rebuild the door opening as well, so I stcked some bricks just inside the opening so I could fill in sand for the form for that section. I put the door form back in place and carved the sand around it to make the proper opening.

I then put a piece of cardboard, held with a bungee and tie down across the front of the entry to hold the rest of sand form in. I carved the wet sand into a nice inverted funnel shape leading to the chimeny. My entry is pretty shallow, so hopefully this shape will prevent most of the smoke from escaping out the front.

[charger10s]

The next step was the clay mixture, as before, we made several batches by mixing sand and clay with water on a tarp. That process has been the most labor intensive part of the entire build, but it's still pretty fun.

After the entry was covered, we put a second layer on the dome, then covered it all with wet towels and tarps to slow down the drying process.

[charger10s]

Over the next 3 days, we kept the towels damp, spraying them down 3 or 4 times a day. The temps here have been around 110 everyday, so this was a bit of a challenge. I'm glad it was a little cooler when we did the first layer of the dome.

On Monday, after 2 days of drying, I dug out the sand and was able to remove the door form with no cracking or anything falling down on me! Woohoo! I was smarter this time, and got that stuff out before everything became hard and stiff.

Tuesday, removed the towels to see how it all looked, and it looks great! No major cracks, and the entry and vent look great.

I took a few pictures trying to show the vent from below, hopefully you can understand what you are looking at.

So, now it is only covered with a tarp, and I'll let the Arizona dry heat work on it for a few more days. I anticipate the first fires to come this weekend! I am planning to follow a similar firing schedule to what is in the plans.