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Ravenscrag Slip Calcined

Silty fusible low iron clay

OxideAnalysisFormula
CaO9.53%0.567
MgO2.90%0.240
K2O4.60%0.163
Na2O0.56%0.030
TiO20.45%0.019
Al2O317.26%0.565
SiO263.57%3.529
Fe2O31.23%0.026
Oxide Weight334.00
Formula Weight334.00
If this formula is not unified correctly please contact us.

Ravenscrag Slip is quite low in plasticity and can be used raw in recipes that do not call for more than about 50%. But where recipes employ more they could crack on drying (because of the shrinkage of this material). In these situations it is better to tune a combination of raw and calcine Ravenscrag that gives you the drying hardness and suspension properties needed while not shrinking too much.

The chemistry of this material is slightly different than for raw Ravenscrag Slip. This calcine material does not lose any weight on firing, so it supplies more of each of the oxides to the fired glaze (almost 10% more).

To calcine a ceramic powder simply fire it high enough to destroy the plasticity but not so high as to sinter it (the sintered powder will have agglomerated particles that have bonded, this grit will not pass your screen and will thus affect glaze surface quality). In the Plainsman studio we fire uncompacted powder in thin slip-cast bisqued bowls that hold about 650 grams each. We fire them to 1000F (Cone 022 or red heat) at 100F per hour and hold for 10 minutes (the calcined material turns red and is devoid of moisture). If you fire in larger or heavier containers soak longer, long enough so that little or no black raw powder remains in the center.


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By Tony Hansen

XML for Import into INSIGHT

<?xml version="1.0" encoding="UTF-8"?> <material name="Ravenscrag Slip Calcined" descrip="Silty fusible low iron clay" searchkey="" loi="0.00" casnumber=""> <oxides> <oxide symbol="CaO" name="Calcium Oxide, Calcia" status="" percent="9.530" tolerance=""/> <oxide symbol="MgO" name="Magnesium Oxide, Magnesia" status="" percent="2.900" tolerance=""/> <oxide symbol="K2O" name="Potassium Oxide" status="" percent="4.600" tolerance=""/> <oxide symbol="Na2O" name="Sodium Oxide, Soda" status="" percent="0.560" tolerance=""/> <oxide symbol="TiO2" name="Titanium Dioxide, Titania" status="" percent="0.450" tolerance=""/> <oxide symbol="Al2O3" name="Aluminum Oxide, Alumina" status="" percent="17.260" tolerance=""/> <oxide symbol="SiO2" name="Silicon Dioxide, Silica" status="" percent="63.570" tolerance=""/> <oxide symbol="Fe2O3" name="Iron Oxide, Ferric Oxide" status="" percent="1.230" tolerance=""/> </oxides> </material>


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