1) Water Smoking Stage in Firing
In the ceramic bodies after completing all the process the firing process begins with the expulsion of the mechanical/physical combined water which is not removed by drying. The mechanical/physical water is nothing but the water used in the Shaping process of the ceramic articles. Most of this water is removed in the drying process after completion of all Shaping process. However a part of residual water remains in the body which has to be removed in firing process in the pre-heating stage in the kiln.
In continuous kilns like ring ovens, Tunnel kilns this is done by passing over hot combustion gases produced in the firing zone of the kiln. The heat from the waste gases thus helps in pre-heating the unfired ware. During this stage the water (physical) gets evaporated from the ware. No changes takes place in the clay body during this period except the more intensive drying out which enhances the mechanical strength.
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