Next to lime and soluble salts, the other impurity in the clay is too much sand or mineral fragments. Since sanitaryware manufacturing is based on slip casting process, the presence of sand and mineral granules in clay is considered to be a serious contamination.
The small silica or any other mineral granules in the sanitaryware bodies causes localized thermal stresses which lead to a serious universal problem in sanitaryware manufacturing called – ‘DUNTING’. However these impurities can be removed by clay beneficiation process. But one has to study the economics of the process involved before mining the clay.
The next impurity in the clay is too much organic matter. This gives out problem of too much gases during firing.
To be contd……
