GP20 Nepheline for Matte and Full Polished Glazes
A matte glaze that comes from underfiring is a defect waiting to happen — dry, patchy and different on every kiln car. A matte that comes from controlled crystallisation is repeatable.
Technical Requirements
- Controlled devitrification rather than incomplete melting
- Complete melt before crystallisation begins
- Low iron and titanium so colour stays clean
- A thick, bubble-free melt for polished glaze layers
Why This Flux
CaO 5.34% drives the matte
Calcium-alumina-silicate crystals form on cooling, creating a smooth and uniform matte surface.
15.63% total alkali ensures complete melting
The glaze melts fully first, then crystallises on the way down.
15-25% of formulation weight
The working range technicians use for matte glazes; zinc oxide enhances the effect.
Polished glaze layers 0.5-1.0 mm
High alumina for hardness, balanced flux for a bubble-free melt, low iron for colour clarity.
Grades We Recommend Here
GP20Nepheline Powder GP20 High Expansion
A glaze-maker's nepheline — high calcium, highest total alkali in the range
K200Nepheline Powder K200 Ultra White
The lowest iron grade we produce, for bodies that have to fire white
Where the Material Comes From
More Application Guides
Feldspar & Nepheline for Art Pottery & Studio Ceramics
Studio ceramic bodies and experimental glazes
Application GuidesFeldspar & Nepheline for Container Glass (Bottles & Jars)
Cost reduction + durability improvement
Application GuidesFeldspar for Electrical Porcelain Insulators
K-feldspar high viscosity for shape retention
Application GuidesFeldspar & Nepheline for Fiberglass Production
Alumina source for E-glass and insulation
Application GuidesFeldspar for Opaque & White Ceramic Glazes
Optimal matrix for zirconium opacifiers
Application GuidesFeldspar for Vitreous China & Hotel Ware
Dual flux approach for commercial tableware
Questions From Matte and Polished Glazes Producers
Which grade should I start with for matte and polished glazes?
Most customers start with GP20 and K200. We ship 1-5 kg samples of each grade you want to compare, with a Certificate of Analysis so you can check our numbers against your own laboratory results.
Can I get samples before ordering?
Yes. We ship 1-5 kg of each grade by DHL or FedEx at our expense. Samples reach most international destinations in 5-7 days and each one includes a Certificate of Analysis.
What is the lead time?
Production runs 7-14 days from order confirmation. Standard grades are normally held in stock, so container loading often starts within 3-5 working days.
What quality documentation comes with a shipment?
A batch-specific Certificate of Analysis covering XRF chemistry, particle size, moisture and fired whiteness at 1200 degrees C. We send it for approval before loading, and originals travel with the shipping paperwork.
Send Us Your Current Recipe
Tell us the flux you use now and the defect you are chasing. We will recommend a grade and a substitution ratio for a first trial.