Differences between the surface and bulk of glass melts. Part 2. Influenceof redox ratio on the surface properties of silicate melts

Density and surface tension of iron containing sona-lime-silica and natural glass (calcium aluminosilicate) melts,were measured using the sessile drop and pendant drop arrangements under various atmospheres including reducing (4%H-2/96%Ar), partially oxidisirzg (dry air) and wet (air saturated with water vapour) atmospheres. In addition, to create melts with various redox ratios, some of the samples were pretreated under either reducing or oxidis ing atmospherees. The general trend is an increase in density and surface t ension of the melts with the reduction of iron from Fe3+ to Fe2+. The Fe+ i n four-fold coordination forms preferentially on the melt to lower the surf ace tension.