The presence of entrapped air in the clay articles hinders the drying operation by disrupting the capillary streams and cutting of the water remote from the surface. During drying the trapped air tends to expand on heating to a much greater extend than the clay and the pressure produced may break the piece. Hence the removal of air from the clay body by passing through a vacuum pug mill is very important in most of the heavy size pieces.
The speed of drying is dependent on the capacity of the ambient air for taking up water vapour. It depends on the temperature, relative humidity and on its constant replacement by air currents.
To be contd…………
