The effect of an increasing content of SiO2 in ternary glasses of compn. Na2O.CaO.xSiO2, where x = 2, 3, 4, 6, was investigated using DTA to evaluate the effect on the glass transition temp. and devitrification. The work is part of a more general study on the devitrification of soda-lime-silica glasses for glass-ceramic manuf. from cheap raw materials. Increasing the SiO2 content increased the glass transition temp. and thermal stability of the glass. Glasses with the compn. x = 4 and 6 softened remarkably before crystn. The glass with x = 2 underwent bulk crystn. with an activation energy of 95 kcal/mol from homogeneous bulk nuclei which developed with a max. nucleation rate at ∼550°
