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The Hoffmann Principle for brick firing from Oxford Clay

  1. The kiln is built with a series of chambers. Flues are built from each chamber to the huge chimney stack; this allows the fire to move from chamber to chamber under control of air flows from the chimney.
  2. 64000 green bricks are loaded into each chamber. The bricks are already stacked and are moved into position by forklift trucks.
  3. Once loaded, the entrance to the chamber is sealed with a "wicket" made from old bricks and a sealant.
  4. The fire in the kiln gradually reaches the bricks (as controlled by the flues). Once the temperature reaches 400 degrees centigrade, the bricks ignite and fire themselves at a temperature of 950 degrees centigrade.
  5. Once the combustible elements within the bricks have burnt off, the kiln is kept at the correct temperature by the addition of small amounts of coal dust added through bungholes in the top of the kiln. Only a half a tonne of coal is needed to fire one chamber.
  6. When the bricks are fired, the fire is moved to the next chamber.
  7. After the chamber has cooled, the "wicket" is broken open and fresh air is admitted to the kiln to cool the bricks and finish the process.
  8. The kiln is then unloaded using forklift trucks. The entire process takes eleven days.
  9. The whole process is continuous: bricks are added and unloaded from the chambers daily and the kiln itself is never allowed to go out.

East view of the southernmost remaining chimney. © Simon Cornwell 2009