Frequently Asked Questions:
What is cob?
Cob is simply earthen masonry. It is made by mixing sand, clay, water and straw. It is used to make ovens, benches, garden walls and even entire homes.
How does a cob oven work?
Simple overview of the building to baking process:
- Build a base
- Lay a brick hearth
- Pile sand to create a form (think of a giant sand castle).
- Cob is built up around the sand form (walls are approximately 9 to 10” thick).
- Cut the door and remove the sand
- Let the oven cure: simply a process of allowing the cob to dry before lighting a fire
- Once the oven is dry, you can build a fire on the hearth for approximately 2.5 hours) to ‘soak the cob’ (i.e. the heat is absorbed by the thick cob walls).
- Bake! For large, pizza- focused parties, we’ll often leave a small fire burning on one side to keep the temperature in the 700 degree (Farenheit) which we call ‘live fire cooking’. If we are baking bread, roasts or other more normal temperature foods, we’ll clear all the coals & ash out before sliding in our breads/ dished on the peel (big pizza shovel) which we call ‘thermal cooking’.
Load your pizza, bread, roasts, veggies, fruit leather, etc until no heat remains (3 to 6 hours of intense heat; noticeable heat a full day later). Note: a good firing will bring the oven up to 700 degrees Fahrenheit. This is a mighty hot fire and perfect for baking pizza.
We’ve hosted 18 person 5 course dinner parties on one thermal cook firing of our oven, and fed over 50 people pizzas from live fire cooking.
How long does the heat last?
This depends on a few things. First, it depends on the design of your oven and how much insulation it contains. The more it is insulated, the longer the heat will remain. Secondly, it depends on how long you “soak” the cob (i.e. how long you heat it up with fire). A good 3-hour firing will produce sufficient heat for plenty of baking/cooking. Thirdly, the more you open the door, the more heat you’ll lose.
Now, once you begin cooking you will lose heat through two ways. First, heat is lost over time. It travels through the cob walls and eventually heats the outside of the oven, then the outdoors (this can take 3 or more hours though, and continue for up to 24 hours). Second, you lose heat by cooking. This happens because you’re literally eating up the heat. As you load cool, uncooked foods, the food absorbs heat, so when you remove it to eat it you are eating that heat. The more you cook, the more heat that is gobbled up.
A 3-hour firing will generate enough heat to cook a round of pizzas (say 2, 4, even 6), a round of bread (say 6 loaves), a couple pies and maybe some muffins. The cooler temperatures that remain are ideal for dehydrating foods, leavening bread, starting yogurt, and even drying your next round of firewood. You can make productive use of all the heat!
Why is there no chimney?
A chimney may be added but it is not necessary. Much experience has revealed that a door cut at the right proportions provides ample oxygen (comes in along the floor), while also giving room for the smoke to escape (at the top of the door). It’s pure magic!
Can you even have a fire in a city?
Depends. Many municipalities are starting to change the rules around outdoor fires. Generally speaking though, cooking appliances tend to be exempt. There are some simple rules for constructing a fire pit or woodburning appliance, like a cob oven, but they are fairly intuitive. Check with your local region before beginning to build. The main requirement is that the fire be at least 2 metres away from a structure. We have built quite a few ovens in Calgary, so if this is where you live, you can find more information at: www.calgary.ca and type “fire pit” in the search option.
Doesn’t burning wood create air pollution?
Pollution is a symptom of too much. One car and it’s not a big deal. 500,000 cars and we get pollution. The same goes for burning wood. Not everyone is going to want a cob oven and for those that do, I’ll argue a great deal more good comes from it than the little bit of smoke generated in the firing process.
Cob ovens are about forming connections. They’re about connecting with nature – even our nature – as fire is the one element that we’ve been able to harness that sets us apart from our ancestors and all other species. They’re also about connecting with people and with our communities. Fire brings people together and cooking in a cob oven is an unreal experience – the flavours, the beauty, and the great stories that are shared when friends and neighbours eat together – are what make these earthen structures so spectacular. Cob ovens also carry with them a rich history that spans the globe, including deep roots in the Quebecois culture in Canada. And more than 70 years ago, on the prairies of Saskatchewan, my grandmother regularly baked bread for her the community in a neighbours cob oven.
They may produce a little smoke but their efficiency comes in bringing friends and neighbours together, producing ear-to-ear grins as people eat mouth wateringly taste food, and by simply carrying forward a rich and delightful history.
How do I get an oven?
- Take a workshop (visit our what to expect at a workshop page here) through Dirt Craft and DIY.
- Open your space up for an educational opportunity by hosting a group of students for a workshop. You supply materials, drinks and snacks. For more on hosting, see our hosting guidlines here.
- Have a custom oven built for you. Email firstname.lastname@example.org for a quote.