Oven Build Part Two

Right with the oven base done, the hard bits begin. To make the oven the right shape, a sand former must be built. First I drew the largest circle possible using a piece of chalk and string. I started to pile up sand in this circle, my aim was to get this sand pile to about 45cm high and shaped a bit like half an egg shell. In my first attempt I made the sand too wet so I would get my ovoid sand pile to about the right height and it would collapse under its own weight. I left it over night and started again the next day, and was able to create the desired height and shape.
Before continuing with the next stage, I placed a layer of news paper over the sand dome, wet so it would stick. This news paper comes in handy later.


The picture above is me starting the mix the Cob for the oven walls. The first layer of the oven is not proper cob, as it is only clay and sand (about one clay to two sand), the next layer will contain straw also. My clay came from the subsoil in the garden, it is mostly clay in my local area, so I was quite lucky I did not have to look far, the sand however came from a builders merchant. It is easiest to mix the cob with your feet, I do not think there is any other way to mix it really, but it is a lot of fun to get all messy. It is best to do the cob mixing on a tarpaulin or something similar, as it makes it easy to turn the cob over to make sure the clay and sand are thoroughly blended together. Once it looks well mixed, take a handful and make a ball, then squeeze 50 times (while keeping it a ball), then drop it from waist height, if it stays in shape, the mix is ready to use. If when dropped it cracks or falls apart, its is probably to dry, or not enough clay, if it flattens when dropped then it is probably to wet, either add a bit more sand, or leave it to dry out before using. I found that mixing all the cob for an oven is too much work for one person, I should have tried harder recruit to my friends. Taking handfuls of cob at a time, I built up the wall of the oven pressing downward on the cob, not on to the sand dome. The wall should be about 10cm wide, all the way around. Once I had covered the whole sand former with cob, I patted the new cob so it was smooth and ready for the next layer.

I shall continue tomorrow.