When glaze compositions are prepared as aqueous suspensions, the frit is wet milled in an alumina ball mill with additives and water to obtain a glaze suspension with the appropriate rheological properties for subsequent application. Viscosity of the suspension is usually adjusted by adding deflocculants, binders and suspension agents. This paper examines the partial dissolution of Si, B, Ca, Mg, and Zn in glaze suspensions that contain a zirconium white frit, using two deflocculants (a sodium tripolyphosphate and a sodium polyacrylate), under different operating conditions (dry milling the frit in a jet mill and wet milling the frit in an alumina ball mill). Samples were taken at different times to study the ageing of the glaze suspension; the elements in the liquid fraction of the glaze suspension were analysed and a rheological study of the prepared suspensions was conducted. Partial dissolution of the frit was then related to the change in rheological properties. Viscosity was found to vary with time. Further tests were subsequently conducted in which a calcium salt was added to a sodium carboxymethylcellulose (CMC) solution. The variation in viscosity was found to be caused by a change in dissolved CMC behaviour, which could be due to a change in CMC molecular conformation.
