The pre-treated tiles are now placed on so-called H-cases. These will allow for the heat of the furnace to be conducted around the tile bodies in an ideal manner. Before the tile blanks reach the tunnel furnace, they must pass through the pre-heater.
15 Tunnel furnace
The tiles are then baked at temperatures exxceeding 1,000° C in a long tunnel furnace. This process takes several hours to be completed. As a result of the enormous heat, the clay is compressing and hardening. The tiles are shrinking a bit in the course of this process, but at the same time, they are becoming more resistant.
The casting rate can mainly be attributed to two kinds of processes in the furnace:
a) Transformation of crystals at 550° -600° C
b) A certain proportion of hyaline melted mass is created that cements the unmelted parts to each other in the course of the cooling.