|Monthly Tech-Tip |
Modified: 2023-10-31 23:48:28
A celadon recipe affording slurry and fired properties control (because proportions of raw and calcined materials and frit can be adjusted)
|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. Fine tune the thermal expansion by changing the frit (e.g. frit 3134 for higher expansion, 3249 for lower, 3124 for nuetral).
Since this glaze is 90% clay, roast half of the Alberta Slip complement to reduce the drying shrinkage (for application to bisque ware). If applied to leather-hard ware it should be OK as to use raw Alberta and Ravencrag Slips.
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 G2881B, simply an Alberta Slip:Ravenscrag Slip 50:50 mix (the Ravenscrag Slip portion was roasted). 5% Ferro Frit 3134 was added to get a little better melting (to produce a high gloss). This produces a good celadon with great working and application properties. Inside glaze: Pure Ravenscrag Slip (mixed 50:50 roast and raw).
Roasted Alberta Slip (right) and raw powder (left). These are thin-walled 5 inch cast bowls, each holds about 1 kg. I hold the kiln at 1000F for 30 minutes. Why do this? Because Alberta Slip is a clay, it shrinks on drying (if used raw the GA6-B and similar recipes will crack as they dry and then crawl during firing). Roasting eliminates that. Calcining to 1850F sinters some particles together (creating a gritty material) while roasting to 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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|By Tony Hansen|
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