The soluble salts in clay can be detected by scum or white stain which appears when the clay is wet down to the plastic state and then allowed to dry up. The other impurity which disqualifies clay for sanitaryware manufacturing is ‘Lime’.
Lime or bits of limestone cannot be tolerated in clay. The clay contaminated with lime, when used in a sanitaryware body during firing gives out a serious problem of bloating. Bloating is considered as a highly serious problem in sanitaryware manufacturing process.
It is very difficult to remove lime from the clay, especially if the lime is in small particles. The presence of lime can be easily found out by doing a simple test wherein the clay is dropped into a beaker containing hydrochloric acid solution. If lime is present, effervescence or bubbling will be noted.
To be contd……
