Modification Date: 2016-09-11 21:21:50
Member of Group: AS10
By adding a little iron to 100% Alberta Slip you can make an iron crystal glaze.
|Alberta Slip 1000F Roasted||50.0||48.5%|
|Red Iron Oxide||3.0||2.9%|
|Rate (C)||Temp (C)||Hold (Min)||Step|
Typically this type of glaze is made by adding up to 15% iron oxide to a transparent glaze. However using Alberta Slip, you only need 3% iron (this is an advantage because 10% iron flocculates the glaze, requiring the addition of more water which in turn causes crawling). Adjust the iron to get the amount of crystal development and metallic appearance desired. In reduction the extra iron will flux it more so melting should be good.
This is fired in cone 10R. The effect becomes more intense by 5%. To achieve this same effect using Ravenscrag, which has much less natural iron content, 10% added iron is needed (which is, of course, much messier to work with).
Roasted Alberta Slip (right) and raw powder (left). These are thin=walled 5 inch cast bowls, fired to 1000F and held it for 30 minutes. Why calcine? Why 1000F? 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. And 1000F? Calcining to 1900F sinters particles together (creating a gritty material) while 1000F just does not. But note the difference: The raw powder has an LOI of 9% (looses 9% weight on firing). 1900F-calcine has zero%. 1000F-roast has only 3%. So we need 6% less (9%-3%) of it than of the raw to supply the same chemistry. For example, if a recipe calls for 1000 grams of Alberta Slip: Use 500g raw and 456g 1000F roast (500*.94).
Out Bound Links
In Bound Links
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<recipeline material="Alberta Slip" amount="50.000" unitabbr="g" conversion="0.0010" added="0"/>
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By Tony Hansen