Monthly Tech-Tip | No tracking! No ads! |
A customer was having serious trouble with this cone 6 glaze recipe shivering. A quick check of its chemistry and calculated thermal expansion revealed the reason: It has the lowest thermal expansion we have ever seen! The reason is the high spodumene and talc levels. Adding the 3% cobalt, this is also among the most expensive we have seen. It also raises leaching flags with both limit recipes (e.g. very low clay content, high talc and spodumene) and limit formulas (stratospheric levels of Li2O and MgO coupled with plenty of cobalt).
The hard panning problem can be fixed easily: Supply the same amount of Li2O from lithium carbonate (only 10% is needed so the overall recipe cost is reduced), that makes room in the recipe for clay (to supply the lost Al2O3 and SiO2 from the spodumene). Second, introduce KNaO at the expense of MgO and Li2O, that will greatly increase the thermal expansion and reduce or stop the shivering.
Glossary |
Limit Recipe
This term refers to critical thinking ability that potters and technicians can develop to recognize recipes having obvious issues and merit, simply by seeing the materials and percentages. |
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