My quest to make a beautiful rocket oven

This is out at the farm, and I don't get to go there when I'm on call for a week at a time, but this past weekend I went out there to see, and take my own pictures.  Here you can see our Beauceron, Tilly, and one of the steers in the background.  We have 7 Dexter cattle: a young bull, a heifer, an experienced cow and her calf, and finally three steers from a different farm that was dissolving their herd.

There's still a lot more to do.  I need to find all the tiles that fell off in the moving process and re-attach them.  I need to grout the piece, and then it would be smart to waterproof it in some way.  I want to tile the other three sides of this box.  The whole thing needs to be trimmed, and the roof needs to be shingled and trimmed. The bottom part needs to be wrapped in chicken wire and cobbed.  

Also, right now the door bumps into the first row of tile when you open it.  I'm going to have to chip away at or remove a couple of tiles so that the door can open past flat, for easy access inside.

Still, it's nice to see it coming together!

This is just amazing.  Your vision for this and how you created it... thanks for sharing!

Life goes on, whether we are ready or not!

It's been ages, I know, but I've finally grouted the mosaic for the front piece.  I was stuck on not being able to find all the tile pieces that fell off when it was moved, but I realized yesterday that it's only going to get colder and the mosaic is less likely to fall apart if it is grouted.  Since I last posted the roof was covered in cedar shake shingles and we've built a roof over the stairs to the basement that also affords some shelter for a person out on the deck.

That ^ was back before Halloween.  Yesterday was when I finally grouted the mosaic.

I ended up wasting my cobalt pigment in the grout.  I mixed it into the "dove grey" grout mix ($3.99 from the Habitat Restore) as a powder, then added some black iron oxide pigment (both of the pigments were purchased from a ceramic supply place). I wanted a dark midnight blue. It looked blue-grey, but when I added water it went BLACK.  So, the cobalt is in there but you can't appreciate it.

It was 52 degrees and sunny when I left Portland, but it was 38 degrees and foggy when I got to the farm.  My hands got SO cold applying the grout!!  I couldn't take any pictures without ruining my phone.  Once I finally had grout all over the thing, it was time to wipe it down with a big sponge.  I boiled water in a pot and added that to the bucket of water - dipping my hands in steaming warm water was such a relief!

I grabbed the 5 gallon bucket that's been serving as a trash can in the ranch house bathroom, because it was full of barely used paper towels.  Those helped quite a bit in revealing the tile after wiping with a wet sponge.  The grouting was tricky because my "tiles" were of all different thicknesses.  I needed to excavate some of the tiles with my fingers, but luckily I was wearing surgical gloves so it was do-able.

Smearing all that grout into all those crevices took a while, and the sun goes down at 4:30pm these days, so I finished the project by LED spotlight.  I got to hear Dewey, our Maremma mix LGD, start his nightly round of barking.  He'd go "bark-bark-bark-bark-BARK" and to me it sounded like "a big dog lives here!  a big dog lives here!"  The coyotes barked back, but from far away.

After I was done, I found out my gloves had developed tiny holes.  My cuticles and parts of my fingers are stained black from the iron oxide.  Damn that's a powerful pigment!

That is beautiful!

Thank you for the update, Julia!

Julia Winter wrote:I got about this far done, and then the Kickstarter was over.
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Julia, this is beautiful. I'm inspired to use some beautiful plates I have that I never use for this - That is what the flowered piece is, right, the center of a plate? Now I need to figure out how to get/build a rocket oven.

Yes, Erica.  I started with a fancy (cracked) plate and used tile nippers to cut off the rim in pieces.  Those pieces (from more than one plate, actually) make up the second row of mosaic there.  In between are solid yellow pieces I cut from yellow bathroom tiles.

The center of the lower right blue themed circle is also made from pieces of a fancy plate.  I put a request on NextDoor for cracked/broken pottery and got a few really nice pieces.

Julia Winter wrote:

The center of the lower right blue themed circle is also made from pieces of a fancy plate.  I put a request on NextDoor for cracked/broken pottery and got a few really nice pieces.

What a great idea! I think I once gave away a bunch of beautiful broken pots to someone making a similar request, though thru a last-gen method...maybe email?

Awesome! It's very creative idea.

Some time I can use this idea of beautifying my cob rocket stove using broken tiles.

So, last week I found a HUGE morel mushroom.  This is sadly the first time I've ever actually found a morel, and it was in my back yard, growing out from under a piece of cardboard "mulch."



This calls for a pizza! I brought the giant mushroom and other fixin's out to the farm. The pizza oven is still working, although the decorative aspects are still not finished.  Time to start the fire.



Then it's time to make a morel and salami (and sweet potato) pizza.  Oh yeah, it had pesto and pumpkin sauce to boot.



Into the oven with you.  We got the oven to 500 degrees, but couldn't get past that.  I need some very dry wood (water boiling out of the ends of the sticks is a bad sign).



And, just a few minutes later - delicious pizza.  I made two pizzas, with very similar ingredients since they were so delicious.  
Yummy pizza!



As you can see, the mosaic for the front piece is grouted, and I've ground away a bit of tile so the door opens, but the framing is still not in place, the sides aren't tiled and the J-tube has not yet been cobbed.  

Time to cob the oven!

First, we had to make cob.  We bought two bags of sharp sand (sharp river sand works better than softer beach sand or sandbox sand) and mixed out cob in small batches.  First stomp together the sand and the clay (which was clay rich subsoil from near the barn):

We followed the advice about cob in Ernie and Erica's book about building a Rocket Mass Heater and ended up with a sand rich mix that held together when dropped from 4'.  Then we added chopped straw and stomped a bunch more. On Sunday it was cold and rainy, but stomping warmed us up!

We applied cob to the top of the heat riser first, because we had to incorporate the hardware cloth into it to seal off the oven box from critters.  So, it was some top-down and then bottom up cobbing.  Unfortunately, I didn't realize I should be painting the concrete block with slip until Monday.  I'm just going to hope that the chimney surround sticks together because it is a contiguous wrap, on all 4 sides, and stabilized by the metal frame on top and maybe by the metal mesh on the bottom.  On Monday I realized what I needed to do and started using a clay slip:

You can also see (up there^^) that I used some scrap concrete brick to build a foundation for the cob, to keep it well off the ground.  This cob is mostly for aesthetic reasons, although it may help the heat riser stay hotter and prevent air leaks.  This picture is just a better view of the mesh (I had to cut it to tailor it around the heat riser) and a closeup of the slip on the concrete blocks.  

Some of the oven had no room for cob - basically the front vertical surfaces.  Painting those with slip helps everything hang together visually.  The white clay slip that we used as mortar held on just fine through the winter, so I'm hoping this red brown slip will also endure.  If not, it's easy to re-apply.

I finished most of the cobbing on my own (my kids went on strike and refused to give me another day) on Memorial Day.  By the end, I had a nice layer of cob over most of the "rocket" part of the rocket oven and the hardware cloth was stapled to the frame or incorporated into the cob.

We fired it up that evening after reading that it's a good idea to fire the oven while the clay is still wet, so that it can expand when the oven expands.  This can help avoid cracking later on.  We didn't get it up past 500 degrees, just to 400 degrees.  Hopefully most of the expansion happens in the first 300+ degrees of heat gain.

I'm planning on a plaster coat and I'm pondering decorations, although I'm OK with the solid brown color.  Oh, and speaking of solid color, I bought some high-heat black spray paint and painted the oven door.  This oven is approaching beautiful at this point. It's interesting how when you fix up one part, it draws the eye to the other unfinished parts!  This is going to be a work in progress for some time.  Right now, we need to prioritize a wood shed.  We need more very dry wood.

Julia,
this is so very lovely! hence you get an apple. enjoy

we'd like to build a rocket oven, hubby doesn't like the looks of the drum. he wants to build it all with stone. that stone would take a long time to heat up, i presume?

The metal barrel allows for quicker cooking times. how long to heat the oven before the pizza went in? pizza was ready in minutes. that's amazing.
thanks so much for sharing your progress. =)

Thanks Sena! (Yeah, I get overwhelmed and busy sometimes, it's been 14 months.)

We are still using the pizza oven, there was a break due to drama but the difficult tenants have been discharged and we're back to almost weekly pizza parties!  

The oven heats up really fast, in less than half an hour, and we got it to 600 degrees last weekend, using nice dry wood that was split into kindling.  I love this oven.  I still highly recommend building one.

I talked about the rocket oven in a recent podcast.  It has developed some spalling at the bottom, where the white hot flame from the heat riser hits the bottom of the inner barrel that serves as the white oven.

Do you think it would be hard to find a stainless steel inner drum that size?  Otherwise, I wonder if an internal stainless steel bent sheet deflector would work to help distribute the heat a little to help eliminate the focused hot spot and avoid the spalling?

This is now on my growing list of cool things I saw at base camp that I REALLY need to get built.