© 2020 The Author(s). Published by IOP Publishing Ltd.Zircon (zirconium silicate; ZrSiO4) is an essential compound of sanitaryware glaze due to contributions to the final properties of the surface. In this study, the effect of zircon particle size on the surface properties (microstructural development, opacity, roughness, hardness and bacterial activity) were studied. Initially, zircon powder was milled by planetary mill at different times (0-25 min) and added to an industrial sanitaryware glaze recipe. Four different glaze suspensions were prepared, applied to a sanitary ware body and sintered in an industrial tunnel kiln at 1220 °C for 16 h. The effect of milling is clearly observed via SEM investigations by uniform distribution of zircon grains with a size reduction to 0.38 μm. This uniform distribution and reduction in particle size provides improvements in opacity (L∗ value measured as 91.47) and hardness (Hv was 6.3 (±0.3) GPa) values. According to AFM studies, the average roughness decreased to 10.94 nm when a 25 min milling process was used. The antibacterial activities of two samples (milled for 0 and 25 min) were analyzed against Escherichia coli and Staphylococcus aureus. Although both samples did not show any antibacterial activity, the number of viable bacteria on the samples milled for 25 min decreased drastically compared to the one not milled. A smoother glaze surface facilitated less sites for adherence and accommodation of bacteria and hence a decrease in bacterial colonization was obtained.