Introduction
The term fast firing generally means short firing cycle
and has now become very important in whiteware industries
for reducing the energy consumption and the cost of production
and also for. higher production flexibility. 1 At present
in India, the firing schedule for vitreous sanitaryware is
roughly 12 h. However, the tile industry is practising 30
min firing schedule. The Si02 content in sanitaryware body
improves the strength and chemical resistance and the
higher amount of Si02 leaves free cristobalite phase and
that encounters sharp volume changes due to reversible
transformations. This necessitates slow and careful firing
of the products. 2 The sanitaryware, during firing undergoes
shrinkage in different directions ( -14%). Due to highly complicated
shapes of the sanitaryware, a faster cycle produces
a lot of strain in the body leading to the formation of cracks.
The high thermal expansion coefficient of vitreous sanitaryware
makes them unsuitable for quicker firing cycles.3
Hence, to achieve faster firing cycle, it is necessary to minimize
shrinkage and suitably alter the thermal expansion
coefficient of the body. Wollastonite and talc were added
in the body composition to reduce firing shrinkage, thermal
expansion and firing range.4 The minimum flux used in a
body makes it more acid resistance but may lead to
incomplete reaction when faster firing cycle is used.
Optimization of the flux content is another parameter to
achieve a faster firing cycle. The present work is an attempt
to study the different clay sources in detail for the selection
of suitable raw materials and the body formulation for
developing sanitaryware under fast firing conditions. The
role of flux content and the influence of minor additives
were studied with respect to the total shrinkage and porosity
to optimize the body formulation made by casting. The
developed products were compared with a standard one.