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Alternate Names: K-Feldspar, Orthoclase, K Feldspar, Potassium Feldspar
Oxide | Analysis | Formula | |
---|---|---|---|
K2O | 16.92% | 1.00 | |
Al2O3 | 18.32% | 1.00 | |
SiO2 | 64.76% | 6.00 | |
Oxide Weight | 556.74 | ||
Formula Weight | 556.74 |
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 In Granodiorite
Tap picture for full size and resolutionOrthoclase Crystals
Minerals |
Leucite
Hardness: 5.5-6 Density: 2.5 K2O 21.50%, Al2O3 23.50%, SiO2 55% An alumino-silicate common to gr |
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Minerals |
Anorthosite
A plagioclase feldspar rock containing ilmenite. |
Minerals |
Sanidine
A potash feldspar mineral. |
Minerals |
Microcline, Anorthoclase
A potassium feldspar. |
Oxides | K2O - Potassium Oxide |
Typecodes |
Feldspar
The most common source of fluxes for high and medium temperature glazes and bodies. |
Typecodes |
Generic Material
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. |
Typecodes |
Materials used in Denmark
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Materials |
Mahavir Potash Feldspar
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Materials |
Eureka Feldspar
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Materials |
A-3 Feldspar
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Materials |
F-20 Feldspar
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Materials |
KM71 Feldspar
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Materials |
FM6 Feldspar
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Materials |
FK45 Feldspar
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Materials |
Calcium Feldspar
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Materials |
Feldspar
In ceramics, feldspars are used in glazes and clay bodies. They vitrify stonewares and porcelains. They supply KNaO flux to glazes to help them melt. |
Materials |
Custer Feldspar
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Materials |
Soda Feldspar
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Materials |
261-F Feldspar
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Materials |
SP-G Feldspar
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Materials |
Clinchfield #202
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Materials |
G-20 Feldspar
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Materials |
G-200 Feldspar
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Materials |
G-40 Feldspar
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Materials |
Yankee Feldspar
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Materials |
Madoc Feldspar
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Materials |
Elbrook Feldspar
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Materials |
Maine Feldspar
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Materials |
MC Na-200 Feldspar
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Materials |
NC-4 Feldspar
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Materials |
Keystone Feldspar
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Materials |
Sil-o-spar
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Materials |
Cornwall Stone
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Hazards |
Feldspar
Feldspars are abundant and varied in nature. They contain small amounts of quartz (while nepheline syenite does not). |
Frit Softening Point | 1250C M |
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Frit Softening Point | 1200-1250C M |
Density (Specific Gravity) | 2.56 |
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