Why clay idols develop cracks?

Clay Idols

The clay used by potters to make pots contain many nano particles.  These particles absorb water drops.  Water drops are the reason why the clay has the softness to mould in to any shape.  Water drops work as binders between the particles of clay.  Mixture such as thee which have more number of solid particles and less number of liquid binders are called gel.  When idols made of these substances are kept in sun for drying, the water drops evaporate, the bonding between the clay particles is gone and cracks are developed.  When the idols are dried in shadow, cracks will not develop.  If these clay idols are burned in kilns, though the water evaporates, new bondings develop between the clay particles and the idol becomes strong.