Saturday, November 3, 2018

Beyond Cob Wood-fired Ovens

bricks fitted over sand mound/form

sand as the form for later brick setting
A long-time friend built a small cob oven a few years ago.  As cob will, it didn't keep the heat for long, developed cracks, and although it was very inexpensive, wouldn't allow his partner to start baking any quantity of bread for sale.A long-time friend built a small cob oven a few years ago.  As cob will, it didn't keep the heat for long, developed cracks, and although it was very inexpensive, wouldn't allow his partner to start baking any quantity of bread for sale.
using off-cuts of bricks to create solid mass
Interior inspection and clean-up
Slim bodies only!
As his long-time friend, I gave him some hundreds of stray fire bricks and off-cuts from the precision bricks I'd previous cut for the custom ovens I build for my clients.





The four-cornered dome


Applying the vermiculite and Portland cement insulating layer


The result is a hybrid.  The mouth and flue assembly is from a cast-refractory company, who shall remain unnamed, that I represented early in my oven career.
A slow warm-up to drive the water out of the mortar
We mounded sand as you would if you were covering it in clay and sand, the cob method.
But instead of clay and sand going over the sand, we began mortaring fire brick chunks up and over the mound, filling in behind with refractory mortar.  As with cob ovens, the sand was removed when the dome was finished and set.


We also chose to make the floor rectangular but build a four-cornered dome so that the maximum space would be available for bread baking.  Low cost vermiculite and Portland cement had been cast under the floor bricks and more of this was applied to the exterior.

Subsequently, a box will be built around the oven and the cavity filled with loose vermiculite.  Roof over all.

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