The effect of TiO₂ on the high-temperature viscosity of soda-lime-silicate glass have been investigated. The silica-rich part of quaternary can be taken as a template for a wide variety of technical glasses. The measurements were performed using a rotational viscometer. The viscosities were recorded from 1550 °C downwards to 930 °C. The entire viscosity-temperature curves were fitted to the Angell-Rao viscosity equation and thermodynamic data were calculated using the method of Ojovan and the liquid fragility according to Angell. As TiO2 is replacing SiO2 it has a slight suppressing effect on the viscosity until the limit when Na2O/TiO2 ratio is less than 2, indicating a transformation of the structure of TiO₂, a remarkable increase in the fragility and viscosity is observed for the calculated low temperature region. The change is not as evident for the high-temperature region. CaO replaced by TiO2 gives almost no effect on the viscosity, however, as it approaches Na₂O/TiO₂≈2 it tends to crystallize at temperatures of 1000-1050 °C.