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Custer Feldspar

Potash Feldspar

Alternate Names: Custer Spar

OxideAnalysisFormula
CaO0.30%0.033
K2O10.00%0.664
Na2O3.00%0.303
Al2O317.00%1.042
SiO268.50%7.128
Fe2O30.10%0.004
LOI0.30
Oxide Weight618.54
Formula Weight620.40
If this formula is not unified correctly please contact us.
DENS - Density (Specific Gravity)
Sp VAL
1 2.6
SIEV - Sieve Analysis 35-325 Wet
Sp TOT 35M 48M 65M 100M 150M 200M 325M NOTE
1 100           0.3% (0.5% max) 4% (5% max)  
pHPW - pH for dry powder
Sp Valu
1 8.0

This is one of the main feldspars used in the ceramic industry in North America. It is used in industries such as abrasives, sanitary ware, floor and wall tile, dinnerware, pottery, and electrical porcelain. It is a ceramic grade, high potash feldspar and is available in crude, 200, 325 mesh and chip form.

Since 2012 we have been getting independent reports of a reduction in the potash content (below that stated on the data sheet). Traditionally Pacer, the manufacturer, has reported it as around 10% (as is shown in the chemistry given here, and from their online data sheet). However Ron Roy claims that, from his independent analysis of specimens over time, around the year 2000 the K2O content dropped to about 7.5 (with no accompanying change in the Na2O). Pacer disputes this. The chemical analyses they provide with individual shipments of material continue to report K2O, Na2O and Fe2O3 levels at quite similar to those stated on their data sheet. Additionally, they have a page on their website named "Clarification of Custer Feldspar Chemical Composition Data" in which they claim their analysis is, and has been, accurate.

As with any feldspar, production users should be vigilant to do sieve analysis testing to spot any iron bearing particles in the plus 100 mesh range.


Feldspars, the primary high temperature flux, melt less than you think.

Feldspars, the primary high temperature flux, melt less than you think.

A cone 8 comparative flow tests of Custer, G-200 and i-minerals high soda and high potassium feldspars. Notice how little the pure materials are moving (bottom), even though they are fired to cone 11. In addition, the sodium feldspars move better than the potassium ones. But feldspars do their real fluxing work when they can interact with other materials. Notice how well they flow with only 10% frit added (top), even though they are being fired three cones lower.

Comparing the melt fluidity of two shipments of Custer Feldspar

Comparing the melt fluidity of two shipments of Custer Feldspar

Melt flow test comparing Custer Feldspar from Feb/2012 (right) with Mar/2011. Custer Feldspar does not melt like this by itself at cone 10. It was mixed 80:20 Feldspar:Ferro Frit 3134. This test demonstrates that the material has been very consistent between these two shipments.

Out Bound Links

In Bound Links


By Tony Hansen

XML for Import into INSIGHT

<?xml version="1.0" encoding="UTF-8"?> <material name="Custer Feldspar" descrip="Potash Feldspar" searchkey="Custer Spar" loi="0.00" casnumber="12168-80-8"> <oxides> <oxide symbol="CaO" name="Calcium Oxide, Calcia" status="" percent="0.300" tolerance=""/> <oxide symbol="K2O" name="Potassium Oxide" status="" percent="10.000" tolerance=""/> <oxide symbol="Na2O" name="Sodium Oxide, Soda" status="" percent="3.000" tolerance=""/> <oxide symbol="Al2O3" name="Aluminum Oxide, Alumina" status="" percent="17.000" tolerance="16.5 min"/> <oxide symbol="SiO2" name="Silicon Dioxide, Silica" status="" percent="68.500" tolerance=""/> <oxide symbol="Fe2O3" name="Iron Oxide, Ferric Oxide" status="" percent="0.100" tolerance="0.05"/> </oxides> <volatiles> <volatile symbol="LOI" name="Loss on Ignition" percent="0.300" tolerance=""/> </volatiles> </material>


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