Ceramic suitability of clays depends mainly on their
characteristics such as mineralogy, chemistry, granulometry
and plasticity as well as the firing conditions:
temperature, soaking time, heating rate and atmosphere.
To assess a clay suitability for manufacturing bricks or
roofing, floor and wall tiles empirical diagrams involving
grain size distribution , mineralogical constitution
[۲-۷] and chemical composition [8-10] are often in use.
Taking for instance the evaluation of the ceramic
suitability of raw clay by using the Winkler’s diagram ,
no attention is paid to their mineralogical and chemical
compositions as well as to firing conditions. This is partly
applicable for the remaining known diagrams. In all
cases, by using the empirical methods, the technological
magnitudes of the foreseeable clay products could not be