The perfect dome
A sand form supports the layers of the oven as it is being built. It also creates the interior shape of the oven. In almost all ovens, the interior should be dome-shaped. We chose to use sand with a high quality of stickiness to make shaping the sand form easier. After the first layer of the oven is laid over the sand form and is somewhat dry, the sand can be removed and the interior of the oven will be revealed.
We sifted our sticky sand into a wheel barrow to remove some of
the larger pieces of rock and debris. Then we wetted the sand to a formable
composition and began piling it on the firebrick. We laid it inside the circle
we had drawn for the interior of the oven, starting out gently as not to disturb
the firebrick. The sand piled on higher and higher. What started out as a
handful of clumps soon turned into a formidable dome.
Building the Sand Form
Liz was inspired with the idea to shape the interior doorway of the oven also. As we created the dome, we shaped a short parabolic tunnel leading out toward the extended brick-lip which created a doorway for our oven.
Our sand form took about two good afternoons of work. It seemed like a simple task at first (it was), but what was amazing was the amount of sand it took for us to complete it. It took about five cubic feet of sand to make the whole dome.
After the sand was shaped (to incredible excellence), wet newspaper was put over the form. This would serve as a barrier between the sand form and the first layer of the oven, showing exactly where the sand form stops and the first oven layer starts. The newspaper also helps the sand form keep it's smooth shape if it's not going to be worked with for a while. Don't leave it unworked for too long. The sand form will dry out, loosing some of it's shape and ability to stick to itself. Also, if the newspaper gets dry it is hard to work with. Consider wetting your form if it's going to left dormant for a while.
Applying Wet Newspaper
That's all for now. Check back later and see the rest of the steps it took to create our beautiful oven.