Shape Deformation in Sanitary Ware: Controlling Melt Viscosity with Flux

Sanitary ware products (toilets, washbasins, bidets) have complex 3D geometries that must maintain precise dimensional accuracy through firing at 1200-1280 degrees C.

Symptom

Sanitary ware products (toilets, washbasins, bidets) have complex 3D geometries

Root Cause (Flux-Related)

Shape deformation — slumping, warping, or distortion — occurs when the glass phase becomes too fluid at peak temperature, allowing gravity to pull the heavy body into an unintended shape. The flux material directly controls melt viscosity: Na2O-rich fluxes (like pure nepheline) produce more fluid melts, while K2O-rich fluxes (like K-feldspar) produce more viscous melts

Solution

For sanitary ware, the solution is to use K-feldspar (SY101) as the primary flux for its high-viscosity potassium glass phase, supplemented with moderate nepheline (K200, 10-15%) for additional alumina that further increases viscosity and for whiteness. A typical sanitary ware body: 25-30% ball clay, 15-20% kaolin, 10-15% nepheline K200, 10-15% K-feldspar SY101, 15-20% quartz

Understanding This Defect

Shape deformation — slumping, warping, or distortion — occurs when the glass phase becomes too fluid at peak temperature, allowing gravity to pull the heavy body into an unintended shape. The flux material directly controls melt viscosity: Na2O-rich fluxes (like pure nepheline) produce more fluid melts, while K2O-rich fluxes (like K-feldspar) produce more viscous melts. For sanitary ware, the solution is to use K-feldspar (SY101) as the primary flux for its high-viscosity potassium glass phase, supplemented with moderate nepheline (K200, 10-15%) for additional alumina that further increases viscosity and for whiteness. A typical sanitary ware body: 25-30% ball clay, 15-20% kaolin, 10-15% nepheline K200, 10-15% K-feldspar SY101, 15-20% quartz. The dual-flux approach provides both vitrification (from nepheline) and shape stability (from K-feldspar)..