The aim of this study is to establish a better understanding how the ulexite addition to frit composition instead of boric acid affects the thermal behavior and surface properties of transparent wall tile glazes. Frit mixtures were prepared with 0 wt%, 3wt%, 6.5wt% and 11.5wt% ulexite content instead of boric acid followed by applied on wall tiles, firing at 1121°C/31 min. the thermal behavior of frits was evaluated by hot stage microscope. The obtained glazed tiles were characterized by dilatometer, Harcourt and Autoclave tests. It was shown that ulexite decrease the critical temperatures of the standard glaze and increase the coefficient of thermal expansion. No crack formation was detected in Harcourt and autoclave tests.