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Alberta Slip 1000F Roasted

Alternate Names: Roasted Alberta Slip

Oxide Analysis Formula
CaO 6.40% 0.38
MgO 4.20% 0.35
K2O 3.80% 0.14
Na2O 2.40% 0.13
TiO2 0.30% 0.01
Al2O3 16.50% 0.54
SiO2 58.20% 3.26
Fe2O3 4.90% 0.10
LOI3.00%
Oxide Weight 325.21
Formula Weight 335.26

Related Information

Roasting Alberta Slip at 1000F

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.

Will this crawl when fired? For sure!

This high-Alberta-Slip glaze is shrinking too much on drying. Thus it is going to crawl during firing. This common issue happens because there is too much plastic clay in the glaze recipe (common with slip glazes). Clay is needed to suspend the other particles, but too much causes the excessive shrinkage. The easiest way to fix this is to use a mix of raw and calcined Alberta Slip (explained at albertaslip.com). The calcined Alberta Slip has no plasticity and thus much less shrinkage (but it still has the same chemistry). Many matte glazes have high kaolin contents and recipes will often contain both raw and calcined kaolin for the same reason.

Links

Materials Alberta Slip
Materials Alberta Slip 1900F Calcined
URLs http://albertaslip.com
AlbertaSlip.com

By Tony Hansen


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