Water absorption is the most commonly specified quality parameter for ceramic tiles: porcelain below 0.5%, standard floor tiles 0.5-3%, wall tiles 6-15%.
Technical Details
This number is controlled primarily by the flux content in your body formulation β more flux means more glass phase, more glass phase means less porosity, less porosity means lower water absorption. The relationship between nepheline percentage and water absorption is approximately linear within the practical working range: each 1% increase in nepheline content reduces water absorption by approximately 0.3-0.5 percentage points (depending on other formulation factors and firing temperature). So if your current formula with 18% nepheline produces 2.5% absorption and your target is 0.5% (porcelain grade), you need approximately 4-5% more nepheline β increase to 22-23%. If your current feldspar-based formula produces 3% absorption and you want to reach 1% without changing firing temperature, switching from feldspar to nepheline (at 82-85% weight ratio) effectively adds 20-30% more flux per batch, which can reduce absorption by 1-2 percentage points. Our technical team can provide more precise calculations based on your specific formulation and kiln conditions..
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