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Left is G3933A, an Alberta Slip based glaze. Right is Amaco PC-32, Albany Slip Brown. They are likely using a similar base recipe, but the difference is added lithium carbonate to supercharge the melting. That converts it to a type of reactive glaze (one that changes its appearance with differing thicknesses). Where thick in the recesses it crystallizes to a much lighter color. On contours, it runs thinner amplifying the brown body color. The use of lithium explains why PC-32 is more expensive. Lithium prices are rising so fast it may not continue to be practical for manufacturers to continue making some lithium glazes (hopefully this one is safe since the percentage is relatively low).
Left is G3933A, it is an 80:20 mix of our matte and glossy cone 6 base recipes (plus a mix of iron oxide, tin oxide and rutile). The body is Plainsman Coffee Clay. Because of repeated issues with crawling a project was started to create the same effect using Alberta Slip to supply as much of the chemistry as possible. Along that road, the opportunity arose to add lithium (to duplicate Amaco PC-32, a classic Albany/Lithium recipe). That is the glaze on the mug on the right, G3933G1, it has 6% lithium carbonate. Lithium is a super powerful melter, turning this into a very reactive glaze! In 2023 a 500ml jar of this glaze required about $7 worth of lithium carbonate. That makes this an ideal candidate to prepare as a brushing glaze - a benefit of that is better control of thickness, a key to the visual effect this gives.
Materials |
Lithium Carbonate
A powerful melter very valuable in ceramic glazes. It is 40% Li2O and has an LOI of 60% (lost as CO2 on firing). This material in now incredibly expensive. |
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Materials |
Albany Slip
A pure low plasticity clay that, by itself, melted to a glossy dark brown glaze at cone 10R. It was a popular glaze ingredient for many decades. |
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