clay bread-oven

Midsummer Farm Life in the P-Cove

Keynote Blogger: Matthew Atkinson, Seed to Spoon Collective

It's BIG FOOD time for the Seed to Spoon Collective: the greenhouses and fields are nearly throwing vegetables at us these hazy September days.  This is no time to be lazy, though!  Tomatoes, potatoes, squash, cucumbers (and the like) don't need as much constant attention as the salad greens and tender baby veg took up in spring and early summer, so there is extra time to spend on a few interesting projects at the Farm... building a clay bread-oven!
Inspired by the hearth-baked, whole wheat sourdough bread that John Bell keeps feeding us - we've decided to secure our own sustainable source of those golden loaves.  The foundation for our outdoor oven is a 7-foot wide, giant rock and boulder base that tapers to a flat, 5-foot circle that is 3.5 feet tall.  It kinda looks like an alter, and incorporates a BBQ grill at the base.  We'll add a camp-fire ring later.  We moved about 2.5 tonnes of rock and dirt to build it, and all that material was picked out of the upper fields very early this spring!!  You can dance a jig up on there, and not a pebble will shift!
Next, we scavenged a pile of old brick to create a ring atop the foundation, and began the process of "making" clay.  Well, it's more like isolating clay.  If you stir a few sifted shovels of dirt up really well in a bucket of water (break up all the lumps with your fingers), it will settle into different layers, each of which serves some purpose in the building process. It takes a while to settle, so we used the rocks, gravel & pebbles that sifted out to shore up the greenhouse foundation and smooth out a few paths while we waited.
Now, to the bucket...
Any organic matter left in your sifted soil will float to the top, and you can skim it off and squeeze out the water like a sponge.  This material makes excellent insulation fluff when mixed with clay-slip to make a mud that fills the brick ring.  Sawdust works well too, and in the long run, it pretty much burns out and leaves a clay sponge thermal shield so our oven heat doesn't get sucked into the thermal mass of the rock foundation!  For an even better insulated oven floor, we buried a layer of bottles (on their sides) within the insulation mud.  The insulation mud will also be packed onto the outside of the oven walls, but first - back to the bucket...
Next, gently pour off the layer of dirty water, but stop before you lose the silty clay mud that has settled beneath.  Ideally, save that water to tweak the consistency of future mud batches, but at least use it to water the garden.  The pond-bottom looking muck below the water is what we're after: clay-slip.  This gets mixed with organic material or sawdust (for insulation mud), or with sand (for a mud that absorbs and holds heat, and is used to build the actual oven walls and floor).
The clay-slip extends down almost to the bottom of the bucket, depending on how finely you screened and sifted your dirt in the first step.  At the very bottom of the mucky bucket will be an inch or two of increasingly gritty (from sand to pebbles) silty mud.  This grittier muck can be mixed with ashes from the fireplace to form a decent mortar for the rock wall foundation, and we used it to set the brick insulation-containment ring in place, too!  Push your fingers gently into the mucky bucket - your fingertips will tell you where the line is between smooth, fine clay-slip and the rougher mortar material.
So far, we have collected a giant bucket of clay-slip, and completed the insulation layer of the oven floor.  It will have to dry out for a few days before we can proceed with the heat holding oven-mud floor, and then build up and insulate the domed walls.  In the meantime, we've purchased the only new material required: manufactured, fire-proof, food-grade oven bricks that we'll lay out to form the actual firing and cooking surface within the oven.
It's been an amazing process to see a shovel-full of dirt yield no less than five different building materials.  And that's only the components we can easily discern with our fingertips!  I've not even begun on the wonder of that shovel-full of dirt "building" the fields full of vegetables.  Veggies that one day soon, will grace the top of a pizza hot from the Seed to Spoon Collective's outdoor bread oven.  We'll eat it as an appetizer while the stew-pot simmers and the grill sizzles.  After tidying up, we'll roast marshmallows, and warm our toes fire-side while drumming a few beats in celebration of twinkling starlight at the end of another lazy, hazy September day at the Farm.  Jealous?
- Matt