Today is the most exciting day of your life. You're going to learn How to Build a Pizza Oven!
When last we met, in part 1 of this series, I had built the base and the sand form for my cob oven and lost my funny bone. It's currently buried beneath a layer of pizza fat.
Now it's time to make the actual cob for the pizza oven. The cob is the material of the first layer of the oven. The cob is the layer that will heat up (the thermal mass). The insulating layer, which comes after the cob is what holds the heat in.
As I keep saying, these tutorials are meant to be a reference to how I built my oven. If you want to build your own I highly, high, HIGHLY recommend you buy the book Build Your Own Earth Oven and watch architect Sigi Koko's 4 part video series on How to Build a Cob Oven.
The book will give you accurate measurements for your oven so it will vent properly, and accurate amounts of how much building materials you need for various sized ovens as well as a ridiculous amount of pointers. Sigi's videos will have the book all make sense and give you a great visual reference.
My posts, will give you a good idea of the work involved and the confidence that you can indeed do it yourself.
Also there's a lot of stomping involved so it'll give you great legs. Don't get excited. Those will disappear when the stomping stops and the pizza eating begins.
The materials to make cob.
Straw (straw is only used in the insulating layer of cob)
One of the reasons I decided to go with a cob oven for my pizza oven was because the materials are either free or cheap. My town happens to be filled with clay, so I knew all I had to do was dig up my mother's yard to find enough clay to make an oven. Sand, well that's cheap enough and straw goes for around $4 a bale at my local feed store.
If you watch the videos and read the book I recommend they describe perfectly how to see if the clay you've dug up is pure clay, or clay with a certain amount of sand content. Mine, as it turns out, was fairly pure.
The reason you need to know this is because the amount of sand you add to your clay will depend on how much sand the clay already has in it. You're creating ancient cement basically.
The clay and sand (in the required proportions), I believe mine was one part clay to 3 parts sand, are mixed together. Not an easy feat. Or feet. You stomp and jump and turn and toss and jump some more to fully integrate the sand into the clay.
Your mixture needs to be sticky; so enough clay that it will all stick together, but enough sand that once it dries it won't crack apart.
Mixing and testing cob
Is making a cob oven a pain? Yeah. A little bit. Is it fun? You bet. Worth it? DEFINITELY. Here's a quick look at how to mix your cob and test it for the proper consistency
You can see in this next picture that I've placed a layer of newspaper over the sand dome. This is so when I go to dig the sand out to crate the interior of the oven, I'll know when to stop digging. Once I hit newspaper I know I've made it to the cob layer.
Creating the outside of the oven (the cob layer) involves grabbing a handful of the mixture, plopping it down and smashing it with your fist to make it nice and tight. This layer needs to be around 4" thick. Just keep plopping and smashing. Plop and smash, plop and smash.
You'll know you're doing a good job when you look like you joined Fight Club.
Don't worry about it. Suck it up. Show those knuckles off. You're knocking out a pizza oven, Sugar Ray.
Once the cob layer is done, you need to let it dry for a couple of days. Just enough so it won't collapse when you start your next step.
Which is cutting out the door of your pizza oven.
The door needs to be specific measurements (again explained in the book) in relation to the size of the oven in order for the pizza oven to vent properly. If your proportions are right the smoke from the fire inside the oven will roll up to the top of the pizza oven, then roll right out the top of the door.
The smaller your oven, the smaller your door needs to be, the smaller the pizza you'll be able to fit into it. Bigger oven means bigger door which means bigger pizzas.
My oven's door will barely fit a 12" pizza peel. I can fit 2 pizzas in it at a time.
Once your door is dug out you'll discover your original sand form ...
Which you can now dig out. Once you dig that out, you'll have something that actually looks like a genuine wood burning oven and you'll be very, VERY excited. So excited in fact that you'll spend a lot of time running, squealing and shaking.
It's a pizza oven. It's a bread oven. It's the focal point of your backyard, neighbourhood, TOWN, p r o v i n c e, COUNTRY, P L A N E T!
And you built it. With your own bare hands.
Let's move onto the final step of How to Build a Cob Oven, Step 3!