Technology

Spectrum® from Sibelco

16/07/2020

Drawn from Sibelco’s unique deposits in Norway, Spectrum® nepheline syenite enhances the aesthetic and functional characteristics of matt glazes and helps to reduce production costs.

Matt glazes give tiles a wonderfully natural look and open up endless 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. In addition, 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.

Drawn from Sibelco’s unique deposits in Norway, Spectrum® nepheline syenite enhances the aesthetic and functional characteristics of matt glazes in a number of ways, as well as helping to reduce production costs.

  • It increases silkiness and whiteness
  • It improves ink colour development
  • It increases scratch resistance
  • It reduces defaults
  • It lowers the melting temperature.

Improved scratch resistance and lower costs

In comparison to other nepheline products, Spectrum®’s higher alumina content improves scratch resistance. It also means that the glaze formula needs less amounts of expensive calcined alumina, and less clay and kaolin, too much of which can adversely affect glaze slip rheology and aesthetic surface appearance.

When used in place of feldspar, Spectrum® reduces the melting temperature of the glaze (thanks to high levels of sodium and potassium) thereby helping to reduce overall energy consumption. Spectrum® 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, Spectrum® is extremely stable up to 1070oC 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 Spectrum® 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 Spectrum® were easier to clean than those made with other nepheline products.

When whiteness matters, Spectrum® again outperforms alternative nepheline products, thanks to low levels of iron oxide and titanium dioxide (0.21%). And because of the purity of our deposit in Norway, Spectrum® has a higher nepheline content than alternative products and contains no free quartz.

Highest consistency to increase yield and reduce scrap waste

Thanks to the outstanding dimensions of the Nepheline Syenite deposit, and to the well consolidated know how on processing, Spectrum® presents the greatest characteristics of consistency and quality. Spectrum® helps to significantly reduce problems with pinholes, thereby reducing scrap waste after firing. 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 tile.

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