After the Solstice Shakedown, on June 26, 2007, a group of us went to Kiza Park to build a combination ornamental firepit and cob oven. We stayed three days, then returned on July 6 and stayed three more days. High temps every day neared 100º, so what we did in six days (including lots of breaks for frolf) could have been done in two or three by a more-steadily working crew, especially in cooler weather.

We look for rocks

In an arroyo near Kiza Park, we chip off chunks of rimrock. You can see the outcrop below Matt's (white straw hat) shovel.

L-R: Kota, Amy Schaller, Tyson White Plume, Matt Rankin, Laramie, Andrew Kneip, Jeremy Briggs, Alex White Plume

A few of the chunks of rimrock lie at bottom of picture.

Amy and Matt load a rock in Ole Hempy while Jeremy and Tyson watch.

Ole Hempy groans.

We pick a spot

Just to Matt's right (your left) is an ashpile from a bonfire. We decide to build the firepit/oven over that spot.

We begin

This is nearly all the rocks we just gathered in an hour of hard work.

We decide to look for urbanite (discarded chunks of cement slab or bricks).

But first we sit and talk

L-R: Gabe and Mandy White Plume, Matt Rankin, Alex White Plume, Roy and Ramona Crazy Bull, Lori.

We find urbanite

at the Body of Christ Sanctuary east of Porcupine (about 15 miles from Kiza Park).

Roy Crazy Bull, Jeremy Briggs, Amy Schaller, with urbanite in Ole Blue

Ramona and Roy with Harry Riverbottom (no kidding) and Lori

Harry was at the White Plumes teaching some kids how to play polo. They loved it.

We finish the firepit

which is also the pedestal for the cob oven.

The diameter of the inside circle is about 32 inches. The pedestal stands about 3 feet tall.

And we make sure fire will burn in it.

At this point we left (after the fire burned out). The date is June 28.

July 2, 2007

We begin to build the oven.

Ascertaining that the top of the pedestal is close to level (minor corrections can be made later), we find more urbanite--a piece of heavy chainlink fence and some pieces of rebar.

We need something strong enough to support a few hundred pounds of mud without totally closing off the rising heat from the bottom of the oven.

We mix cob

Cob is, like adobe, a combination of sand (or fine gravel), clay soil, straw and water.

We mixed about 4 shovelsfull of local soil with about 6 shovels full of 1/4-inch gravel with enough water to make a modeling clay-like mixture. Then we added as much straw as we could without losing the cohesiveness of the mixture.

This tarp-load needs several turns and stomps before it will be ready.

The oven floor is complete, and finished with clay slip (sloppy mud).

The walls will be built outside the vents, which are open to (and through) the chainlink below them. Our theory is that a fire below will send heat up through the vents to heat the walls and floor of the oven.

The oven door (see below) will provide a way to allow the heated air to flow through the oven.

If that doesn't work, we can build a fire in the oven itself, which is the conventional approach.

We begin the oven dome

The scrap of brown tarp roughly defines the oven floor inside the oven.

The white bucket is the center of the oven space (saves weight), while a dome of sand and gravel is being heaped over it. After the oven dome has dried, we'll pull the sand and bucket and tarp scraps out.

The oven-space form is complete. The interior of the oven will be about 27 inches across at the floor, and about 16 inches tall at the apex of the dome.

We'll lay cob over the tarp, which covers the sand. The rocks are temporary, to keep the tarp on 'til we get some mud on it.

We cut a door outline

I used a serrated-blade kitchen knife that I bought for $1. I wanted to cut through the straw imbedded in the mud and break most of the mud bond at the door seam.

The cob that comprises the door was about 14 hours old at the time, but 100º heat brings cob to "leather stage" pretty fast.

I didn't remove the door, because it was still not dry, and would have almost certainly broken. When it has dried, someone will use the serrated blade again and completely separate the door from its borders before removing it.

Cob workshops with Jeremy are the best. He always brings the frolf.

Note yellow disc at bottom of picture: It's mine; there in two.

And this is the way it is; Friday, July 6, 2007.

We'll be back July 13 to finish up and bake some bread.

Saturday, 15 July 2007

The first order of business is to pull out the door and remove the sand form for the dome.

We built the door too thick; the bottom part was still wet and it broke off. Had to dig that part out with a hatchet.

Having removed the sand from the oven space and cleared the vents through the oven floor, we built a fire.

We put the door back in, leaving a vent at the top of the door for convection.

The air escaping from the vent was easily 400º, meaning that air that temperature was heating the cob mass.

The oven's interior, looking at the roof of the oven.

You can see the pattern of the tarp in the roof. It's smooth and baked hard as a brick.

We heated a frozen pizza in the oven--its inaugural baking.

The fire had burned for five hours; the oven was very hot when we put the pizza in. The doorway was mostly blocked by the chunk of cob door.

However, even leaving the pizza in more than twice as long as the directions said for a 425º oven, it just barely got it hot enough to be good eating.

The door.

Even if it had not broken, it was too heavy for most people to lift into place.

A few bricks or a chunk of 2x12 will work just fine for a door.

Thinking about our experience with the pizza, I think we might have to double the thickness of the dome (the upper walls and roof of the oven) to give it more thermal mass.

More, after Lakota Hemp Days!

Cob the Builder signing off (7/16/07).