Nepheline syenite plays an important role in matt glaze production. Using high-quality materials such as Nepheline can help to significantly improve the functional and aesthetic properties of the matt glaze and finished tile, as well as reducing your overall production costs.
Creating a perfect matt effect
Matt glazes give tiles a natural look and open up different design possibilities. But creating a matt glaze that is also functional (in terms of ease of cleaning and resistance to scratching and chemicals) can be very challenging. Drawn from Sibelco’s unique deposits in Norway, Nepheline enhances the aesthetic and functional characteristics of matt glazes in a number of ways, as well as helping to reduce your production costs. The benefits include:
• Increased silkiness and whiteness
• Improved ink colour development
• Increased scratch resistance
• Reduced cracking
• Lower melting temperature
Reducing waste
The trend towards large format tiles means that manufacturers need to minimise glaze-related pinhole defects in order to reduce costly volumes of fired waste. Nepheline helps to significantly reduce scrap waste after firing due to problems with pinholes. This is even more important when glazing slabs, as a defect on a 1.5m x 3m piece means a lot more wastage than a defective 60cm x 60cm wall.
Improved scratch resistance and lower costs
In comparison to other nepheline products, Nepheline’s higher alumina content improves scratch resistance. It also means that the glaze formula needs less expensive calcined alumina, clay and kaolin, too much of which can adversely affect glaze slip rheology and aesthetic surface appearance. When used in place of feldspar, Nepheline reduces the melting temperature of the glaze (thanks to high levels of sodium and potassium) thereby helping to reduce overall energy consumption.
A higher coefficient of thermal expansion
Nepheline also has a higher coefficient of thermal expansion (CoE) than a standard sodium feldspar, making the glaze CoE more compatible with the CoE of the tile body to improve the body-engobe-glaze fit. In terms of firing temperatures, Nepheline is extremely stable up to 1,070°C whilst sintering and softening points are close to the firing temperature for glazed vitrified tiles (GVT).
Achieving a good balance between ink colour development, matt level and whiteness
Free of magnesia and with a barium oxide content of 0.4, our laboratory tests show that Nepheline enhances digital ink colour development whilst delivering a good level of matt glaze surface. It therefore outperformed other nepheline products in the tests, which either
delivered good colour development but a lower matt, or a higher matt but lower colour development. Our tests also showed that GVT tiles with a glaze made with Nepheline were easier to clean than those made with other nepheline products.
When whiteness matters, Nepheline again outperforms alternative nepheline products, thanks to low levels of iron oxide and titanium dioxide (0.21%). And because of its purity, Nepheline has a higher nepheline content than alternative products and contains no free quartz.
To know more about Sibelco’s Nepheline products, please contact us at ceramics@sibelco.com.
