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Ravenscrag Slip 1000F Roast

Alternate Names: Ravenscrag Slip Roast

Description: Silty fusible low iron clay

Oxide Analysis Formula
CaO 10.70% 0.68
MgO 1.80% 0.16
K2O 3.20% 0.12
BaO 0.30% 0.01
Na2O 0.50% 0.03
TiO2 0.40% 0.02
SiO2 65.80% 3.92
Fe2O3 0.90% 0.02
Al2O3 13.40% 0.47
LOI 3.00%n/a
Oxide Weight 347.19
Formula Weight 357.93


Fully calcined Ravenscrag Slip (fired at 1900F) has an LOI of 9%. However it is not necessary to fire it that high to remove the plasticity (to reduce shrinkage during drying). The website outlines this 1000F roasting process. This version looses only 3% of its weight on firing, so the analysis totals 97.

Related Information

Ravenscrag Slip + 10% talc = fantastic cone 10R silky matte glaze

Two mugs with silky matte glaze

The clays are Plainsman H450 and H550. Firing is cone 10 reduction. A 50:50 mix of roasted and raw Ravenscrag slip was used. L3954N black engobe was applied at leather hard stage (on the insides and partway down the outsides). We call this recipe GR10-C Ravenscrag Talc Matte, it is on the insides of both and on the outside of the one on the left. The outside of the other is G2571A Bamboo, it is also an excellent matte base. The silky matte surfaces produced by these two are both functional (they are very durable and do not stain or cutlery mark). And they are very pleasant to the touch.


Ravenscrag web site
Ravenscrag Data Sheet at Plainsman Clays
Typecodes Clay Other
Clays that are not kaolins, ball clays or bentonites. For example, stoneware clays are mixtures of all of the above plus quartz, feldspar, mica and other minerals. There are also many clays that have high plasticity like bentonite but are much different mineralogically.
Materials Ravenscrag Slip
A light-colored silty clay that melts to a clear glaze at cone 10R, with a frit addition it creates a good base for a wide range of cone 6 glazes.
Materials Ravenscrag Slip 1900F Calcined
By Tony Hansen
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