I live by the sea in East Kent. Our coast faces North. The sea is Khaki green with clay and silt, and usually calm as it is protected by the entrance to the Thames estuary.
I had never heard of a coastal kiln until I started planning this project – but on arrival in West Wales to meet with Joe Finch (Master kiln builder) the first thing I encountered in the wild cove of Cwmtydu was an 18th century coastal Lime Kiln! Apparently they are 10 a penny in that part of the world. Nestled in beside the crashing pebbles and foaming surf of the Atlantic ocean, they are designed to heat quarried limestone to turn it into Lime to provide fertiliser for the nearby fields.
With my head full of the strange symmetry of this encounter I visited Joe Finch for an afternoon of planning and trying things out. Joe had agreed to help me design the muffle and advise me on how to construct it.
I took with me the measurements of the internal dimensions of my gas kiln. Having thought about the problem in 2 dimensions and talked around the idea we went into this ceramics studio to think about it in 3 dimensions. We rolled out slabs using a re-purposed mangle, which saved time and energy.
His thoughts were that with a structure of this size we should need to make something that comes apart in sections, so we were effectively designing a box with extras. We decided on the steps to follow and the order in which the pieces should be made, dried and fired.
The individual sides of the muffle box would need to be made by paddling stiff saggar clay into a frame used as a former to create a dense slab. The lid, the base and the back piece would all be flat slabs of the correct dimensions. The two sides and the front would also have added elements or ‘fins’ to help the whole ‘key’ together. The whole muffle when fired will fit together with ‘seats’ of ceramic fibre in-between each piece to help it to bed down and to make a good airtight seal.
Joe sent me home with a car full of saggar clay which he had previously mixed in his old industrial dough mixer. He uses the following recipe. It will fire to a material with the density and toughness of kiln shelves.
50kgs Fireclay
25kgs Kyanite
25kgs Molochite 16/30mesh
3kgs Cellulose fibre
My next post will be on the logistics of making, drying and firing 6 large slabs of clay that each weigh 25kgs.
