I remember the first time we cooked in our brand-new cob oven. After 10 minutes the loaves came out black. One and a half years of volunteer effort had eventuated into a sculptured monster, something of our deep unconsciousness. With the head of a boar and the back of a stegosaurus, smoke guzzelling out of its flattened snout I couldn't help think that we were doing something ancient. The clay was taken from the immediate environment; the volunteers had gathered on various occasions from a greater circumference. But the one thing that London has in common no matter where you are is clay. An infinite supply of brick material for post-industrial house building as well as all those bridges and canal sides, and miles upon miles of walls and streets, clay has been in our bones since God fashioned man out of it. The oldest bricks date to 7,500 BC discovered around the Tigris region. The fired brick, as opposed to the sun-dried brick, came a few thousand years later. Clay has been traditionally used for earthenware, stoneware, and porcelain in which heat treating it causes a physical and chemical change. Its strong attraction properties allow it to combine with a rich source of positively charged ions making it a very nutritious meal. The only problem is, is trying to get hold of the stuff if you are a plant root. The chemistry gets a little more complicated here but basically it involves hydrogen in soil water and something called cation exchange. But because of its microscopic nature water can be tightly bound to it. This water is referred to as hydroscopic and makes for either a very wet material that expands to a size considerably larger, or a very dry material that sets like concrete during a drought. And this is where cob comes in, for adding a good dose of sand and straw forms an incredibly strong material. The minute clay particles smother the sand and act like a cement, only this material has not been produced by heavy CO2 emitting processes as is the case with cement, a little less with lime. Cob has been used for thousands of years, and has now become a popular material again amongst eco-builders. There are numerous existing structures in and around the world, many in Cornwall and Devon, but it seems that cob has also become vogue with artists. Mixing cob has been done in various ways, not least for reasons to reduce the amount of labour required. Nowadays using a cement mixer works only with pre-desiccated clay, but recently I came up with a novel idea of using solid clay lumps to make a slip, then allowing the clay to settle lower down and pouring off the excess water. This mixed with sharp sand makes a lovely render. The 'mud' hut we built was hessian stretched over a timber frame. The sand acts as a moderator preventing the clay from shrinking too much and cracking whilst drying. The straw binds the material even moreso from inside to out. Cob is not adobe. Adobe is an old Arabic word for mud brick. Cob has to be thoroughly mixed something like 80:20% sand to clay. Bullocks were used traditionally overnight to walk it in whilst they shat over everything; today tractors take their place. But community groups are doing it for themselves now. Because that is what traditional methods invoke, a coming together and feeling the lifeblood of the material in your hands. Such is the case with breathable materials like cob, lime and clay, that living inside these structures puts you in touch with the outside environment; they absorb moisture and give it back. They change their form over time, like a third skin shedding itself.
So here are a few measly pictures even though I have made few ovens in my time. The first pic show my very first oven on the railway line guerilla garden site. Along the top recycled (concrete admittedly) block paving and possible designs. Then the building of our own communal oven which got a face lift a couple of times.This is followed by my last piece Hanuman the Monkey God for the great Spike project in Peckham, London. Note the back of the head with a grill for heating up pots.Worked wonderfully! The next lot show kids making at the BrockleyMax, Hope and Green Man Festivals, and then the oven made in Spain that featured fully in my book with a business case and in depth analysis entitled The Carob Pod: An Anthropological Guide to Permaculture available at the market page.