The glass‐formation region of the soda–yttria–silica system was determined. The glasses within this region were measured to have a density of 2.4 to 3.1 g/cm3, a refractive index of 1.50 to 1.60, Vickers hardness values of 3.7 to 5.8 GPa, softening temperature between 500° and 780°C, and a coefficient of thermal expansion of 7 × 10‐6/oC to 19 × 10‐6/oC. Aqueous chemical durability measurements were made on select glass compositions while infrared transmission spectra were used to investigate the glass structure and its effect on glass properties. A compositional region was identified which exhibited high thermal expansion, high softening temperatures, and good chemic