Monday, October 11, 2010

Inside the Cob Oven: A Look Inside the Cob Oven


Alright clay snowman-looking thing, don't look so excited, we're not done yet but I love the enthusiasm.  It's back to the cob oven and although we weren't able to...

totally finish it just yet, we were able to apply a very important layer and learn about the oven's intricate internal workings.  It turns out that a cob oven is not just an aesthetically pleasing, impress your uncle type of thing.  This work of art is more functional and advanced than I ever thought.  All of our conventional "higher-tech" ovens are just trying to match some of the incredible "settings" that naturally occur in this ancient beauty.  Cob ovens utilize all three of the main varieties of heat transfer: convection, conduction and radiation.  Convection occurs when the hot air inside the oven mixes with the inflow of fresh air from outside.  Conduction occurs with the heat from the bricks touching the food you are baking and finally radiation occurs when the clay and air barriers bounce heat back and forth evenly throughout the baking chamber. 

In order to complete this project, we had to literally become one with the oven's materials.  These buckets of clay and sawdust were not going to blend themselves, so it was time to take off the shoes and socks and step right in.

But this wasn't a task for just one set of feet so I'd like to introduce you to Evan's parents Lauren and Bill and our good friend Meghan, the Public Programs Manager from the Stone Barns crew.

There was much to learn, but there was much to do and so as the New Yorker I am, multi-tasking was in order.  Have you ever tried to write and blend clay and sawdust together?  If you have, please share your story, it must be a good one.

Just like working with dough, you have to knead the clay and sawdust mixture until it is evenly blended.  "Burritioing" helps by simply rolling the tarp back and forth pushing everything together (sorry for the technical jargon, but this is very scientific stuff).

Evan explained that a good way to tell when your cob mixture has the proper consistency is to perform a "drop test."  When you drop a small ball of the cob, you want to make sure it's soft, but not like a pancake and firm, but not like a baseball; somewhere in the middle is perfect.

Sorry little buddy, I know you want to help, but we have too many feet already.  There's just not enough room for all of yours.

Since we ran out of clay last time, we had to add an additional 4 inch layer to the inner oven shell.  To start, we re-hydrated the dry segment with water and layered the new cob mixture on top.

Since the final outer layer will be placed on top of this one, we ran our fingers across this material leaving raised streaks that will eventually help the outer layer bind more easily.

Here we see the mastermind admiring his work of art.  Good work sir, good work.

Evan also described the importance of the specific design of this particular structure, which is called a double chamber.  Although subtle, you can see below that the brick arch and chimney (left) make up the first chamber and the baking portion in the back hump of the oven (right) make up the second chamber.  Without the double chamber structure, all the smoke would have to escape back through the oven's mouth, which ends up blackening the oven's outside and wasting a lot of unnecessary energy.  A chimney allows the smoke from the fire in the back of the oven to mix with fresh air from the front of the oven and shoot out the chimney top creating a cleaner and more efficient baking experience.  Since the heat that comes out of the chimney will be in a controlled space, it will even be possible to sauté vegetables on the chimney while the oven is baking.

For more information on the basic ideas behind the double chamber structure, check out this link: Double Chamber.  


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