Effect of preparation variables of plaster molds for slip casting of sanitary ware

Abstract

A full factorial design was used to evaluate the effect of various preparation conditions for making plaster molds for slip casting of sanitary ware. We investigated the relationships between the processing conditions, microstructure, and final properties of the plaster molds. The results showed that the rheological behavior, and hence, the time during which the plaster suspension is pourable for making the plaster molds (before an important increase in viscosity due to the precipitation of gypsum crystals) were dependent on the preparation conditions. Variations in the chemical composition, pore size distribution, and microstructure explained the statistically significant effect of preparation variables (including the mixing time, water temperature, and water quality). Preparation conditions that promoted high initial viscosity of the plaster suspension (accelerative effect of the setting time) developed less porous structure in the mold that principally increased the compressive strength (16%, deionized water instead of tap water) and the casting rate (9%, water at 25°C instead of 38°C). According to the results are proposed optimum conditions to make the molds while avoiding unnecessary energy use.