Effect of alkaline earth oxides on the firing behavior of porcelain stonewares [Effetto degli ossidi alcalino terrosi sul comportamento in cottura del gres porcellanato]

Abstract

Aim of this study was to investigate the relations between chemical composition and firing behaviour of porcelain stoneware formulations. The effects of magnesia and/or calcia incorporation in varying amounts into a standard stoneware formulations through combined use of calcite and magnesite on firing behaviour was studied by means of a non-contact optical dilatometer. It was shown that suitable combination of magnesite/calcite noticeably lowered peak firing temperature without narrowing the firing range. Peak firing temperatures of these bodies were also at commercially acceptable levels. Further formulations prepared with calcite, kaolin and a local clay high in iron oxide content were also shown to give acceptable chromatic co-ordinates. It was also possible to develop bodies with high whiteness values without employing zircon.