|Monthly Tech-Tip |
Of course, if a recipe only calls for 1-5% lithium carbonate either of these might be candidates to supply the Li2O. However, Petalite is eight times less and Spodumene five times less concentrated than lithium carbonate so to make either worthwhile the prices would need to be eight and five times cheaper. But if a recipe calls for more there is another problem: Petalite is extremely high in silica, which means supplying the needed Li2O from it is almost certainly going to oversupply SiO2. Spodumene will likely do the same. Both are also high in Al2O3 and likely to oversupply that (or at minimum supply the bulk preventing the presence of kaolin in the recipe).
Lithium carbonate is now ultra-expensive. Yet the reactive glaze on the left needs it. Spodumene has a high enough Li2O concentration to be a possible source here. It also has a complex chemistry, but the other oxides it contains are those common to glazes anyway. Using my account at insight-live.com, I did the calculations and got a pretty good match in the formulas (lower section in the green boxes). Then I made 10-gram balls and did a GLFL test at 2200F (notice the long crystals in the glass pools below the runways). Not surprisingly, this recipe is very runny, that's why the tiny yellow crystals grow during cooling. The new version fires very similar, perhaps better. Our calculated cost in 2022 was $17.84 vs. $10.40 per kg. But there is a practical cost: Poor slurry properties. The spodumene sources so much Al2O3 that 70% Alberta Slip had to be dropped to accommodate it! How does one use this type of glaze without ruining kiln shelves? Using a catcher glaze is one answer.
Spodumene is a lithium sourcing feldspar, an alternative to lithium carbonate to supply Li2O to ceramic glazes. Contains up to about 8% Li2O.