The three clear cut stages of drying:
1. Water leaves the pore first enabling the clay platelets to move closer together and the volume of mass is reduced by that of the water given up. The shrinkage is proportional to the water given up, the clay particles have come closer together but no air has yet entered the pores.
2. In the second stage, shrinkage proceeds with further loss of water and reaches its maximum by volume. Air now penetrates the pores replacing without further shrinkage, the water which was in part filling the remaining spaces between the particles. At this stage the body has lost its plasticity and exhibits true elasticity.
3. In the third stage, the film of gel enveloping the particles dries. While water is being lost, the apparent density of the body increases. The air replaces water in the pores.
The art of the ceramist consists in regulating the drying speed without leading to overlapping of the different stages of drying.
