Alternate Names: Neph Sy
Left: Cornwall plus 10% Ferro Frit 3134. Right: Nepheline Syenite plus 10% of the same frit. These are fired at cone 6.
Left: Cone 10R (reduction) Plainsman P700 porcelain (made using Grolleg and G200 Feldspar). Right: Plainsman Cone 6 Plainsman Polar Ice porcelain (made using New Zealand kaolin and Nepheline Syenite). Both are zero porosity. The Polar Ice is very translucent, the P700 much less. The blue coloration of the P700 is mostly a product of the suspended micro-bubbles in the feldspar clear glaze (G1947U). The cone 6 glaze is fritted and much more transparent, but it could be stained to match the blue. These are high quality combinations of glaze and body.
These are porosity and fired shrinlage test bars, code numbered to have their data recorded in our group account at Insight-live.com. Plainsman P580 (top) has 35% ball clay and 17% American kaolin. H570 (below it) has 10% ball clay and 45% kaolin, so it burns whiter (but has a higher fired shrinkage). P700 (third down) has 50% Grolleg kaolin and no ball clay, it is the whitest and has even more fired shrinkage. Crysanthos porcelain (bottom, from China) also only employs kaolin, but at a much lower percentage, thus is has almost no plasticity (suitable for machine forming only). Do H570 and P700 sacrifice plasticity to be whiter? No, with added bentonite they have better plasticity than P580. Could that bottom one be super-charged? Yes, 3-4% VeeGum or Bentone (smectite, hectorite) would make it the most plastic of all of these (at a high cost of course).
The two mugs on the left: Traditional Grolleg porcelain using Nepheline and bentonite (fired to cone 10R). The right: Using New Zealand kaolin, Nepheline Syenite and VeeGum.
Three Cornwall Stone shipments fired at cone 8 in melt flow testers (GLFL test) and compared to Nepheline Syenite. Each contains 10% Ferro Frit 3134.
These were applied to the bisque as a slurry (suspended by gelling with powdered or dissolved epsom salts). The nepheline is thicker. Notice the crazing. This is what feldspars do. Why? Because they are high in K2O and Na2O, these oxides have by far the highest thermal expansions. So if a glaze is high in feldspar it should be no surprise that it is going to craze also.
This Nepheline Syenite GLFL test for melt flow did not demonstrate much of a difference in melting at cone 9 between 270 and 400 mesh materials.
White cone 04 bodies are not vitreous and strong and neither is this. But it is plastic, smooth and fits common low fire glazes. How? 15% Nepheline Syenite (also 50% Plainsman 3D, 35% ball clay and 3% bentonite). The unmelted nepheline particles impose their higher thermal expansion on the fired ceramic. Spectrum 700 clear glaze does not craze and does not permit the entry of water (the mug is glazed across the bottom and fired on a stilt). The mug on the right is made from the same clay, it has been fired ten cones higher, cone 6! Here the nepheline is acting as a flux, producing a dense and very strong stoneware (with G2926B, GA6-B glazes). This is incredible! One note: This cannot be deflocculated and used for casting, soluble salts in the 3D gel the slurry.
|Materials||Nepheline Syenite Unimin|
|Materials||Nepheline Syenite Norwegian|
|Media||Substituting Nepheline Syenite for Soda Feldspar|
Nepheline at Wikipedia
Generic materials are those with no brand name. Normally they are theoretical, the chemistry portrays what a specimen would be if it had no contamination. Generic materials are helpful in educational situations where students need to study material theory (later they graduate to dealing with real world materials). They are also helpful where the chemistry of an actual material is not known. Often the accuracy of calculations is sufficient using generic materials.
The most common source of fluxes for high and medium temperature glazes and bodies.
|Articles||Demonstrating Glaze Fit Issues to Students
Glaze and body can both be adjusted to solve crazing and shivering problems. This describes a simple project to create body glaze combinations guaranteed to craze and shiver to demonstrate the principles involved.
|Oxides||K2O - Potassium Oxide|
|Oxides||Na2O - Sodium Oxide, Soda|
|Oxides||SiO2 - Silicon Dioxide, Silica|
|Frit Melting Range (C)||1100C|
|Body Maturity||This material is generally fluxes better than feldspars and produces whiter burning bodies.|