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 reveals the reason: It has the lowest calculated thermal expansion we have ever seen! The reason is the high spodumene and talc levels. Adding the 3% cobalt also makes this among the most expensive we have seen. To say this recipe looks non-typical is an understatement. And, it raises flags on working properties and susceptibility to leaching in 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), which 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, which will greatly increase the thermal expansion and reduce or stop the shivering.
Glossary |
Limit Recipe
This term refers to sanity-checking ceramic glaze recipes by noting whether materials present or their relative percentages fall outside typical norms for functional ware. |
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Typecodes |
Glaze Chemistry
Case studies where glaze chemistry was used to solve a problem. |
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