INTRODUCTION
CLAYS General aspects
The bodies for industrial production of “traditional” ceramic materials (tiles, bathroom fixtures, tableware) are composed of various typologies of raw materials in amounts characteristic of the product desired. The composition of the body and the conditions of treatment determine the transformations that involve the raw material and mainly define the final characteristics and field of employment of the finished product.
With regard to “traditional” ceramics, the plasticity, i.e. the possibility of lending workability, shape and sufficient consistency to the ceramic item through the various stages of manipulation is obtained by using “clays”. “Clays” is the name generally given to all or more or less compacted sedimentary rocks deriving from alterations of primary rocks, mainly containing “clayey minerals” of micronic dimension and characterized by high plasticity.
The clays are natural systems and thus extremely heterogeneous; they can be classified on the basis of the prevalent clayey minerals and hence we may distinguishkaolinitic, montmorillonitic, illitic, chloritic, chloritic- illitic clays, etc.