The impact of wollastonite and dolomite on chemical durability of matte fast-fired raw glazes

Controlled share of wollastonite and dolomite in the recipe was decisive for achieving raw glazes with a matte surface in a fast-firing process. The surface characteristics were studied for 25 experimental glazes containing 9–39 wt% wollastonite and 0–16 wt% dolomite. The glaze suspensions were applied on raw tiles and fired to 1215 °C in an industrial kiln. The chemical durability of the tiles was measured according to the standard ISO 10545-13. Further, the impact of exposure time on surface degradation was measured for 0.1 and 3 vol% HCl-solutions. The changes in the phase composition were studied with SEM/EDXA and XRD. The surface consisted of wollastonite and diopside, some residual quartz and corundum as well as amorphous phases. Wollastonite crystals severely decreased the durability while diopside crystals provided a durable matte surface. The results give guidelines for manufacturing matte and chemically durable fast-fired raw glazes.