Journal of the european ceramic society vol:30 issue:9 pages:1853-1866
The influence of firing conditions on the chemical composition of the major pyrometamorphic phases of Ca-, Fe-rich Plio-Pleistocene sediments of NW Peloponnese is studied. These sediments have been used in the production of ceramic artefacts for a large historical period and are still in use by the local heavy clay industry. Firing conditions were oxidising (CO/CO2, %, ranging from 0.2 to 4.4) or reducing atmosphere (CO/CO2, %, ranging from 11.2 to 23.0), for a temperature range 850-1050 degrees C. At 850 degrees C, for both atmospheres, fassaite and gehlenite are the predominant new minerals with anorthite and wollastonite also formed in a small quantity. Up to 950 degrees C, the chemistry of minerals in oxidising and reducing conditions does not exhibit considerable differences. Fe3+ is present even in reducing atmosphere entrapped in the structure of fassaite, gehlenite, anorthite. At 1050 degrees C, in reducing atmosphere, more hedenbergite component (CaFe2+Si2O6) incorporates in fassaite, whereas the ferrigehlenite component (Ca2Fe23+SiO7) is absent from gehlenite structure. Fe3+ is detected only in fassaite and anorthite structure. The work concludes with a summary of the results from Part I and Part II, in the form of a reverse engineering table for the determination of the firing conditions in a ceramic body by using analytical information. Three examples are given that compare ancient ceramic sherds with ones reproduced in laboratory conditions and demonstrate the effectiveness of this approach. (C) 2010 Elsevier Ltd. All rights reserved.