With a beautiful Saturday morning dawning and the Child Bride off running a half marathon in Plett with the Knysna Marathon Club, I could really get moving with the clay oven project.
Step one was to cover the sand form from yesterday with some wet newspapers (after re-checking my calculations.)
Next I measured out 1 part clay to 2 1/2 parts building sand. As mentioned previously, I have excavated the clay from my terraced garden, dried it out, crushed it into a fine powder and removed all stones. Here is the dry material before mixing. As you can see I mix on a piece of plastic. It’s then easy to pick up one side at a time and roll the mix to the center.
Then some serious mixing involving the traditional “gumboot dance”. Add water as needed to try and get a final consistency that results in a firm (not too dry and not too wet) mix that should look something like this.
One then works from the bottom up around and around the newspaper covered sand form. Roll a handfull of clay mix, put into place push inwards, push downwards, repeat. I smoothed off the surface after every revolution. This layer (the inner layer) I have made about 60mm thick.
The completed inner layer looks like this.
I am going to leave this overnight to see how it hardens. It is not in direct sun and I’d prefer it to dry slowly, which should prevent too much cracking. The oven is expected to crack in places and one must just fix these cracks as the occur. Other builders have suggested only 3-4 hours before the inner sand form is removed but I think that this is because they have to cut the door aperture. My plan is slightly different and I can’t see any harm in leaving the sand form in longer. Tomorrow, depending on how it is hardened, I’ll probably take out the yellow board that holds the sand form behind the brick door arch.
Enough for now. Time for a beer.