Sanitary ceramic formulations balance three functions: plasticity, structural stability and fluxing. Clay and kaolin provide forming ability and green strength, quartz controls shrinkage and maintains the body skeleton, while feldspar forms a liquid phase during firing and promotes vitrification.
A published industrial Vitreous China formulation contained approximately 22% clay, 30% kaolin, 23% quartz and 25% feldspar, although actual recipes vary with raw-material properties and product requirements.
What Roles Do Clay, Quartz and Feldspar Play?
1. Ball clay: forming and strength
Fine, plastic clay improves suspension stability, casting behavior and green strength. Excessive clay, however, increases water demand and drying shrinkage.
2. Kaolin: whiteness and fired structure
Kaolin supplies alumina and silica and participates in mullite development during firing. Excessive additions may reduce plasticity and green-body handling strength.
3. Quartz: dimensional stability
Quartz acts mainly as a relatively inert filler and helps control shrinkage. Particle size is critical. Research on sanitary ware bodies demonstrated that quartz particle size influences phase evolution, thermal expansion and water absorption.
4. Feldspar: vitrification
Sodium and potassium feldspars generate a liquid phase at high temperature, reducing porosity and promoting densification.
A sanitary-ware study using 50% clay, 25% quartz and 25% feldspar showed that feldspar chemistry, particle size and firing profile significantly affected vitrification. Fine Na-rich feldspar produced water absorption below the study’s 0.5% target and glass contents approaching 70%.
Four Raw-Material Roles in Sanitary Ceramics
Item | Requirement from the Source Draft |
Clay | plasticity, rheology and shrinkage |
Quartz | content and particle size |
Feldspar | Na/K ratio and fluxing behavior |
4 | Verify chemistry, particle size and fired absorption by batch. |
Conclusion
A sanitary ceramic recipe is not defined by one universal percentage. Clay enables forming, quartz stabilizes dimensions and feldspar drives densification. When raw-material sources change, slurry behavior, shrinkage and the firing window should be revalidated before production.
FAQ
Q1: What are the main sanitary ceramic raw materials?
A: Clay, kaolin, quartz and feldspar form the traditional core system.
Q2: Does more feldspar always reduce water absorption?
A: No. Excessive liquid-phase formation can increase deformation and overfiring risk.
Q3: Why should a formulation be retested after changing suppliers?
A: Mineralogy, particle size and impurities can alter casting and vitrification behavior.