The update on the cob oven from Matt, our Youth Engagement Officer. Taken from our blog for young people:
Well well well… it’s been a grand couple of weeks. Biting insects aside, the near wall-to-wall sunshine has continued, making this the best summer I’ve ever had as an outdoor youth worker. Since the last post we have welcomed 24 young people to Brandon Marsh to take part in the remaining stages of our cob oven building project. All those involved had loads of fun and came away as cob oven converts. Most of them will have hopefully finished picking sand and clay out of their toe nails, but a small price to pay for one of the best pedicures around!
The morning of Tuesday 8th July was a nerve-racking one. Weeks of preparation scrounging materials was about to crescendo the moment when a bunch of 12 young people, who were participating in The Challenge, arrived in a minibus to begin their cob building experience. In the end there wasn’t a huge amount of equipment needed: a couple of builders bags cut into cross shapes for the mixing, plenty of plastic buckets and mosquito spray, a couple of wheel barrows for transporting clay and sand, a spirit level and a plank of wood. The most important piece of equipment came in the minibus with the youngsters, and was attached to the bottom of their legs. Mixing cob is done with bare feet similar to crushing grapes when wine making albeit with a slightly more subtle technique akin to a dance floor disco boogie. This process takes time and effort, requiring a fair amount of labour, but on the flip side its sociable and lots of fun. Oh, and have I already mentioned the pedicure?
Before this started however we needed to construct a giant dome-shaped sand castle which would act as a template on which to build the first cob layer. Upon completion this sand would be scraped out of the doorway to reveal the oven cavity inside. The dimensions of the sand castle are important as is the size of the doorway, because since the oven has no chimney, it relies on a convection current inside to draw cool air through the bottom of the opening and expel hot air out of the top. Amazingly we ended up using 100kg of sand in this part of the construction!
Mixing the cob took all day. The ratio for this mixture is 2:1 of sand and clay, although the best method to follow is to tread small pieces of clay into the sand, periodically performing a ‘drop test’ on a ball of the material until it reaches the right consistency. Picking the clay apart helped us to remove any stones which would be liable to explode at high temperatures. The clay we used was dug out of the ground a few miles up the road and is known as Thrussington Till, a clay bed that was one the bottom of a giant lake that filled most of Warwickshire thousands of years ago. One of the great things about building a cob oven is that it connects us to our environment and makes us remember that we still totally rely on the planet to provide us with the things that we need.
Building is done in a spiral working from the base of the sand castle, working around until you inevitably reach the top and completely cover the sand beneath. It requires a careful technique otherwise the layer will be at risk of falling in on itself once the sand has been removed. That however was a concern for another day. Out there in the sun, surrounded by trees and wildlife it was easy to let the worries and stresses of everyday life wash away. We all went away feeling muddy and tired I’m sure, but also that little bit more happy.