Sourcing Li2O from spodumene instead of lithium carbonate comes at a cost

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 to mix this recipe in 2022 was $17.84/kg vs. $10.40/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.

Related Pictures

Sometimes it is better to replace the base in a production glaze recipe

Almost all ceramic glazes are a base recipe with additions of colors, opacifiers, variegators, etc. Our traditional G3933 oatmeal glaze is a good example (recipe on the left). It can produce rich brown silky matte surfaces, especially on dark burning bodies. But problems have emerged, especially a tendency to crawl. Much testing has yet to reveal the reason. Would it be possible to base the recipe on Ravenscrag Slip and achieve the same chemistry? Yes. And some unexpected benefits accrue. In the recipe on the right I sourced MgO (the key to the matte surface) from dolomite and Ferro Frit frit 3249 (earlier tests sourcing from talc were unsuccessful, off-gassing from the talc was puffing up the glaze with micro-bubbles). This G3933E recipe has the same chemistry (I derived it in my account at insight-live.com). It is not likely to be without problems, but it looks identical (with richer color from a little more iron oxide), it does not crawl and it's recipe and chemistry are flexible. It is glossy when cooled fast and silky matte when cooled slowly. The mix of calcine and raw Ravenscrag Slip also enable control over the slurry and application properties. I later tuned this recipe a little more and settled on G3933EF.

Here is why Petalite and Spodumene will seldom substitute for Lithium Carbonate

Lithium carbonate vs petalite vs spodumene

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).

Links

Typecodes	Glaze Chemistry Case studies where glaze chemistry was used to solve a problem.
Materials	Spodumene Spodumene is a lithium sourcing feldspar, an alternative to lithium carbonate to supply Li2O to ceramic glazes. Contains up to about 8% Li2O.
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.

Got a Question?

Buy me a coffee and we can talk