|Monthly Tech-Tip |
Alternate Names: Ravenscrag Slip Roast
Description: Silty fusible low iron clay
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 ravenscrag.com website outlines this 1000F roasting process. This version looses only 3% of its weight on firing, so the analysis totals 97.
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
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.
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.
Ravenscrag Slip 1900F Calcined
|By Tony Hansen|
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