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Potash Feldspar

Formula: K2O.Al2O3.6SiO2
Alternate Names: K-Feldspar, Orthoclase, K Feldspar, Potassium Feldspar

OxideAnalysisFormula
K2O16.92%1.000
Al2O318.32%1.000
SiO264.76%5.999
Oxide Weight556.74
Formula Weight556.74
If this formula is not unified correctly please contact us.
DENS - Density (Specific Gravity) 2.56
GSPT - Frit Softening Point 1250C M

One of the most important materials for medium and high temperature ceramic glazes. Potash feldspars are often not as pure and white as soda spars. A feldspar is typically referred to as 'potash' if there is significantly more potassium than sodium (typically there will be 2-5% Na2O). If the amounts are closer to equal they are termed potash-soda feldspars (or vice versa). Of course, real potash feldspars also have small amounts of CaO, MgO, Fe2O3, etc.

Potassium feldspar melts at around 1200C (higher than soda feldspar) producing a more a viscous melt than does sodium feldspar. It can also produce a crystalline phase (leucite) that contributes to opacity. Thus, in industry, potash feldspars are often used more for matte glazes while soda feldspar is used for glossy glazes.

Glazes high in feldspar (35% or more) are plagued by crazing problems, yet still used by tens of thousands of potters. 'Flux saturated' glazes with more than 50% feldspar may be unbalanced and lack adequate glass former or alumina to create a stable hard glass resistant to leaching.


Orthoclase Feldspar Rock

Orthoclase In Granodiorite

Orthoclase Crystals

Out Bound Links

In Bound Links


By Tony Hansen

XML for Import into INSIGHT

<?xml version="1.0" encoding="UTF-8"?> <material name="Potash Feldspar" descrip="" searchkey="K-Feldspar, Orthoclase, K Feldspar, Potassium Feldspar" loi="0.00" casnumber="12168-80-8"> <oxides> <oxide symbol="K2O" name="Potassium Oxide" status="" percent="16.920" tolerance=""/> <oxide symbol="Al2O3" name="Aluminum Oxide, Alumina" status="" percent="18.320" tolerance=""/> <oxide symbol="SiO2" name="Silicon Dioxide, Silica" status="" percent="64.760" tolerance=""/> </oxides> </material>


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