Tuesday, October 9, 2007


There are several things about my oven that I find, well, amazing.
For one thing, it works! It has no chimney and it doesn’t need one. It draws very well and has from the very first time I fired it up. It draws well even after I rebuilt the door arch – but that’s a story for another post.
It draws well because it was constructed based on the traditional clay ovens of Quebec. The ratio of the height of the door to height of the inside of the oven dome is 63%. (The inside dome height of my oven is 17 ½”. The door is 10 ¾” high.) This relationship means that the cold air is pulled in along the bottom of the doorway to feed the fire and the hot air comes out the top. Works like magic every time. Ingenious. Amazing.
My oven also burns without smoking. If I keep the fire small and hot, it doesn’t smoke. If it is smoking, I know I am doing something wrong – too much fuel, too little flame or wood that is too wet. It took me a while to master the technique.
Another thing that amazes me is that I made it with my hands, with the help of many friends. We didn’t need fancy training or advanced skills. We just needed organization, willingness to play in the mud, and the ability to think through the steps.

There are a couple things I don’t like about my oven.
I think it loses heat a bit too quickly but I haven’t figured out whether that is operator error or something related to the insulation for the base. This assessment is not based on any scientific testing or record keeping. Just a casual observation. Many times when I fire it up, we are baking lots of pizzas to feed a group of folks. The door is open which means the heat has a quick escape route. So this is not a good test. I want to do more baking with the door closed and pay attention to the inside temperature over time. That being said, the interior temperature of my oven then next morning is still 200 degrees. Amazing.
It also takes a bit of time to fire up. I usually fire for at least three hours. The oven does have a fair amount of mass – at least 8 inches of thickness, maybe more, which is probably a factor here. I am not complaining. If I wanted an oven that I could fire up when I come home from work just to cook a pizza, I’d have gotten something with a switch.
It’s the simplicity of this oven that charms me into spending time with it. Simple materials, no moving parts. It doesn’t ask much from me but time. And gives back good food and good times. Not a bad exchange if you ask me.

Tuesday, October 2, 2007

Why An Oven?

I built an oven two years ago in my backyard. I built it out of clay and sand, some water and straw. I made it because I loved the idea - to be able to bake bread in a wood fired oven.

Years ago I read an article in the Chronicle about baker Fran Gage. It said she was up in Sonoma, baking bread in an outdoor, wood fired oven. What fun I thought. But an outdoor oven can cost thousands of dollars and that was definitely not in my budget. Lamenting my disappointment to an architect friend, produced an alternative. She said, "Why not build a cob oven?" and sent me a class announcement. Keiko Denzer had a two day workshop up in Oregon to teach people how to build their own earth oven.

My Oven
It took about 4 weekends to complete and the labor of a group of friends.
It cost between $300 and $500, most of which was spent on food to feed my crew of volunteers.
Items I paid for:
  • Sand
  • Firebrick
  • Chimney Brick
  • Clay Pigments
  • A kid to haul some clay from a neighbor's yard

Items I found, scavenged, got, or otherwise obtained:

  • Clay
  • Urbanite
  • Perlite
  • Rice Straw