When drying takes place, water evaporates into the air leaving behind the dissolved salts and the finest clay particles carried to the surface. The rate of drying does not depend on the pressure of the ambient air but only on its capacity for taking up water vapour. Towards the end of drying the pressure of water vapour in the capillaries increases. Drying stops when the vapour pressure inside the capillaries has the same value as outside. The drying speed comes down after loss of the shrinkage water, since the water vapour needs more time to come out through the longer capillaries.
To be contd…………….
