Baking and Burning of Bricks
Baking and Burning of Bricks :
The firing of bricks in a kiln maybe divided into five stages, viz: (1) Steaming and smoking, i. e. the removal of water and readily volatile organic matter (to 120oC). (2) Decomposition of the clay and the removal of residual volatile and combustible matter (to 700oC). (3) Full fire, the chief object of which is to heat the bricks so that they will not shrink in use (the baking stage, to 1,200-1,400oC). (4) Incipient vitrification (plus 1,150oC). At this stage the more readily fusible constituents of the clay melt and thus seal together the-infusible constituents, producing a glassy finish and reducing the porosity of the resultant bricks (the burning stage). (5) Annealing and cooling. Temperature is maintained until it has soaked right into the bricks, which are then allowed to cool slowly in order to avoid sudden contraction and distortion
