Microstructural and technological analysis of industrially produced porous single-firing bodies Part Ⅰ

摘要

In this first part of research some differences were found among the bodies studied. As far as the mineralogical composition is concerned, we find ourselves face to face with two currents: the Italian one and the Spanish one. In fact the Italian bodies are composed of clays, sands, feldspars and carbonates, whereas the Spanish ones have a different composition with a lot of clay, sand and carbonates, showing completely different technological characteristics. In this type of body, the lack of fluxes is compensated by the use of plastic clays and by greater attention to the particle size distribution, increasing the percentage of fine material. We can also divide the five porous single firing bodies into another two categories: those which present dolomites and those which use calcites. The bodies that use calcites are three: MM, MPP and MT and are completely different from each other both for the quantity of carbonates and for the clays and feldspars used. The bodies that use dolomite are two: MTM and MI; in this case they are very similar having exactly the same components with only slight differences. These two bodies are characterised by an evident anomaly, in fact in the feldspar component, albite stands out; this makes us think that both bodies derive from respective glazed porcelain stoneware bodies with the simple addition of carbonates and the reduction of albite.