Density & surface tension of 15Na2O.11CaO.74SiO2 glass melts (mol%) with additions of 0.5 & 1.0 mol% Fe2O3 were measured using the sessile & pendant drop techniques at various temperatures between 1200 & 1400 deg C. Melts of each composition were prepared under oxidising & reducing conditions in order to study the effect of iron redox state on surface tension. Surface tension measurements were carried out in reducing (96%Ar/4%H2), inert (Ar) & oxidizing atmospheres. Density of the melts increased with increasing iron content & decreasing melt temperature. The surface tension of the iron containing melts was found to be influenced by the atmosphere & its effect on iron coordination. It was determined that melts with high concentrations of Fe3+ are most susceptible to changes in the atmosphere, since Fe3+ can have either tetrahedral or octahedral coordination.
