I was attracted to this project when my grandson showed up at the family farm with a book entitled, “How to Build a Cob Oven.” It described in step-by-step detail how a pizza oven made with mud, straw, and sand could be constructed in two weekends for less than $100. Wow! You don’t get bargains like that these days.
Shaping the oven required building a sand mold that would be covered with layers of mortar and then the sand removed. It was a primitive procedure, but it worked. Cob is usually mixed by foot with sand and straw to get a stiff material.
I had read that the early cathedral designers in Europe, wanting to achieve a large dome had considered this approach, but with an interesting twist. Removing the sand without modern equipment was tricky, so the idea was to leave coins in the sand. Once the dome was completed, they’d turn the peasants loose to scavenge for the coins as they removed the sand. As it turned out, we had to make do with agile onlookers, who thought it was fun to stomp in the mud.
I should have been suspicious when the writer noted that success of the project depended on the number of friends you could involve, their abilities, the weather, and the availability of cob ingredients. No problems there. We have number of friends, who have picked up rocks from the creek bed in exchange for a few meals. And, as a frustrated gardener, I knew there was a lot of clay to be found in the area. As to expertise, well, my grandson and his friend had worked on cob projects at college. What could go wrong?
Over the many weekends that followed our helpers varied. There were several lawyers, a neurologists, a couple of college students and professors, a geologist, and some walk-on politicians. Clearly, there was a deficiency of expertise in our work force. Still, they were an enthusiastic lot, working in anticipation of pizza someday, but settling temporarily for cold beverages. Sensing the messiness of any project involving mud and water, kids and dogs happily joined the fun as well.
Our concrete block base was not a thing of beauty, but it was level and the size to support our project. We would later have it faced by a stone mason with rocks from the creek–a cost the writer on cob oven construction neglected to mention.
As time went on, I became to suspect the instruction book we were following might have been written by delusional hippies, sitting around the campfire in the sixties. The book needed an update, if not a sequel. They had clearly left out some of the finer points of the construction process.
The proper ratio of straw to clay is essential to prevent cracking. Remember the Biblical story of the Israelites being forced to make bricks without straw? It didn’t work because fiber is needed to prevent the clay from cracking when it dries.
The completed oven was perfectly arched and the cob smooth and symmetrical. We even got a few splendid pizzas from the high-temperature oven that baked much like those in the professional pizza parlors.
Then it happened. Cracks began to appear and there was an infestation of borer bees, or carpenter bee as they are often called. After much research on the Internet and bringing in a geologist friend, we determined it would be best to tear out the dome and start over with a little different cob mixture. Fast forward several months. The new cob has been applied, dried, and the oven ready for another test run.