Glasses used as glazes for ceramic bodies will be studied as a function of their composition, with emphasis on two elements, such as Ca and Zn, that show the largest influence on their rheologic behaviour during the heating cycle. The glasses cointain Si, Al, Na, Ca, and Zn. To better check for the individual effect of each element, three different series will be measured: one with no Ca and varying Zn content, one with no Zn and varying Ca content, and one with both elements present and varying. The total scattering data will be modeled with the Empirical Potential Structure refinement approach, that has already been proven effective with glasses with a similar, yet simplified composition (with Si, Al, Na, and Ca). The results have just been published on the Journal of Physical Chemistry B.