Drying shrinkage and apparent specific gravity of the dry ware increases with rising surface tension. But the water content at the critical point and the speed of drying are lowered. When the surface tension is increased the so called secondary shrinkage which takes place beyond the critical point reduces and the drying speed falls over the period of constant drying rate.
Clays with adsorbed H+, Ca2+ or Ba2+ have a comparatively open structure and are more permeable than those with adsorbed alkali ions. Al3+ and Fe3+ clays are more permeable than H+ clays and this is reflected on the speed of drying. The fastest and safest drying is observed with clays charged with H+, Al3+ or Fe3+ ions.
To be contd………..
