Albany slip substitute
Alternate Names: Archie Bray Slip
This material was formulated as a physical and chemical substitute for the late and very popular Albany Slip from New York state. Like Albany, it is a low melting iron stained clay. Alberta Slip is more consistent than Albany was since it is made from a blend of raw materials.
Alberta slip has a slightly lower iron content than Albany had so some glazes may not fire as dark (this can be counteracted by adding additional iron oxide). Alberta slip melts as well and works in most glazes that call for Albany. Alberta slip is more plastic (less silty) so recipes containing larger proportions may shrink and crack during drying (requiring the use of a calcine:raw mix).
Plainsman Clays has made this material for many years and it is established in the market place across North America. It has its own website at albertaslip.com. You can use Alberta Slip at 100% (raw:calcine mix) to create a chocolate brown glossy glaze at cone 10. Many Albany glazes were based on the addition of an active flux that increased melt fluidity so that greenish and yellowish iron crystals grew on cooling. Many black glazes were based on Albany Slip, since it already contained lots of iron only a little more and some extra cobalt or manganese were needed.
The plasticity of Alberta Slip is very helpful in suspending glaze slurries. However if there is more than about 40% (with no other clays), then you must use a raw:calcine mix. The albertaslip.com website has information on how to do the calcining and how to adjust for the change in LOI.
The analysis of this material was changed here in Sept 2013, not because the material changed, but because they switched to an actual assay instead of a calculated analysis.
Information from the Digitalfire Ceramic Materials Database