|Monthly Tech-Tip |
Nepheline Syenite is similar to a feldspar. I have them open side-by-side here in my Insight-live.com account (the blue panels). In the "Analysis" column notice that Minspar has 9% more SiO2 and 5% less Al2O3. Minspar has 12% fluxes and Nepheline has more than 15%. If a recipe does not contain a significant percentage of Nepheline these differences might be tolerated but what if there is 30% or more? There is no combination of materials that has the chemistry of Nepheline (there is no way to take 10% of the SiO2 out of this feldspar, for example). But it is possible to take SiO2 out of a glaze containing Nepheline Syenite. Notice the two green recipe panels below: The changes made to the one on the right harmonize the oxide chemistry with the original on the left. Those changes were significant: 15% more feldspar, 12% less silica and 2% less kaolin. Notice how easy this was using a little chemistry!
You will see examples of replacing unavailable materials (especially frits), fixing various issues (e.g. running, crazing, settling), making them melt more, adjusting matteness, etc. Insight-Live has an extensive help system (the round blue icon on the left) that also deals with fixing real-world problems and understanding glazes and clay bodies.
Substituting Nepheline Syenite for Soda Feldspar
Learn to substitute Nepheline Syenite for Soda Feldspar (and vice versa) using the KNaO concept in Insight. You will see the benefit of in-recipe substitution calculation rather than making general substitution rules.