Study on the densification process of pottery body for building construction (Part 4) - effect of particle size of feldspar on densification

Using the isothermal method, the influence of type and particle size of feldspar, a flux component, on the densification process was investigated in the feldspar-quartz-kaolinite system which was a representative ceramic composition for building construction. Type of feldspar greatly influenced the vitrification temperature. Sodium feldspar vitrified 40 °C lower than potassium feldspar. This is attributed to the different viscosities of the liquid of feldspar. The particle size of feldspar also greatly influenced vitrification; the coarser the particle size, the higher the vitrification temperature was. In addition, it was clarified that the bulk density of the body at the vitrification point decreased as the particle size of feldspar became coarser. These results indicate that the dispersion state of feldspar changes due to its particle size in the body and the coarser the particle, it requires a higher temperature because liquid phase should widely disperse to fill the body and as the increase of temperature, gas pressure of the closed pores increases lowering the density of the body.