The viscosity of four iron-containing silicates with alumina has been measured under oxidizing and reducing conditions over the temperature range 450¿ to 700 ¿C. Initially, the compositions contain approximately 2.5, 10, and 20 mol.% of trivalent metal oxide. The viscosities of compositions with approximately equimolar Fe3+ and Al3+ are compared to those determined for compositions with trivalent cation all Fe or all Al. Then the batch composition calculated to replace one half of the Fe3+ by Al3+ under oxidizing conditions is corrected for the divalent iron present under mildly reducing conditions in forming gas (95% N2-5% H2) and strongly reducing conditions with carbon. In general, the viscosity measured in air was higher than the viscosity measured in forming gas with or without carbon for a given temperature and composition. The glasses prepared under oxidizing conditions had Fe2+/Fe total ratios less than 0.25 and the glasses prepared under reducing conditions had Fe2+/Fe total ratios between 0.27 and 0.91. The viscosities for these glasses can be represented by a Vogel-Fulcher relation for each of the three oxidation conditions.