|Monthly Tech-Tip |
Modified: 2019-03-22 12:05:54
A celadon recipe containing only two ingredients. It affords slurry and drying control because proportions of raw and calcined materials can be varied.
|Alberta Slip 1000F Roast||47.50|
|Ferro Frit 3134||5.00|
This is a celadon that you can tune to your needs. It works well on dark and light stonewares and porcelains. Adjust the proportions of Alberta Slip to Ravenscrag Slip to fine tune the color (more Ravenscrag for lighter color). Adjust the amount of frit to tune the amount of gloss and melt fluidity. Calcium carbonate also works, but may produce more bubbles floating in the matrix. If you fire to cone 11, then no flux may be needed.
You can fine tune the thermal expansion (e.g. frit 3134 for higher expansion, 3249 for lower, 3124 for nuetral).
Since this glaze is 90% clay, you will need to calcine half of the Alberta Slip complement to reduce the drying shrinkage if it will be applied to bisque ware (if applied to leather hard ware it should be OK as to use pure raw Alberta Slip).
At cone 10R this produces an overly melted glaze. It also crazes.
The outside glaze on this cone 10R mug (made of Plainsman H550) is simply an Alberta Slip:Ravenscrag Slip 50:50 mix with 5% added Ferro Frit 3134 (the Alberta Slip is calcined). This produces a stunning celadon with great working and application properties. Inside glaze: Ravenscrag Slip 90%, talc 10% (a matte having an extra ordinary silky texture). Learn more at ravenscrag.com.
Roasted Alberta Slip (right) and raw powder (left). These are thin-walled 5 inch cast bowls, each holds about one kg. I hold the kiln at 1000F for 30 minutes. Why do this? Because Alberta Slip is a clay, it shrinks on drying. Roasting eliminates that, a 50:50 raw:roast mix works well for most recipes having high percentages of Alberta Slip. And 1000F? Calcining to 1850F sinters some particles together (creating a gritty material) while 1000F produces a smooth, fluffy powder. Technically, Alberta Slip losses 3% of its weight on roasting so I should use 3% less than a recipe calls for. But I often just swap them gram-for-gram.
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