Formula: Li2O.Al2O3.4SiO2 or LiAl(Si2O6)
|If this formula is not unified correctly please contact us.|
|DENS - Density (Specific Gravity)||2.60|
|GSPT - Frit Softening Point||1421C M|
The name is from the Greek spodos, meaning burnt to ash. Spodumene is a silicate mineral often referred to as lithium feldspar. Its mineral form is characterized by hard needle-like grains of brilliant white color. It is used in ceramics as a source of lithia.
Lithia is a very powerful flux, especially when used in conjunction with potash and soda feldspars. As one of only a few natural lithium source materials, spodumene is a valuable component in glass and ceramic/enamel glazes (Li2O reduces thermal expansion, melting temperature and viscosity of the glaze melt).
Spodumene is only slightly soluble (in contrast to lithium carbonate). Because spodumene is a natural combination of silica, alumina and lithia it melts better than a chemically equivalent mixture of lithium carbonate, kaolin and silica. Since almost all raw glazes contain kaolin and silica it is normally fairly easy to juggle recipe ingredients in a ceramic chemistry calculation program to introduce spodumene to replace lithium carbonate. Spodumene can also be substituted for part of the feldspar complement in a recipe without disturbing overall chemistry too much (other than substituting Li2O for KNaO).
Some types of spodumene do contribute to the formation of bubbles in the glaze slurry. You can wash spodumene before use to alleviate this issue (mix it well in plenty of hot water, allow to settle overnight, pour off the water the next day and dry it).
Spodumene is a little more readily fusible than petalite since it is higher in lithium.
Lithium carbonate is now incredibly expensive. The glaze on the left employs it. But I was able to source the Li2O from spodumene instead. Spodumene has a complex chemistry, but the oxides that it contains (other than Li2O) 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 melt flow test at 2200F (notice the long crystals in the pools of glass below the runways). And I glazed buff stoneware test (below the flow tests). Not surprisingly, this glaze is very runny. That's why the tiny yellow crystals grow during cooling, they produce the gold effect this recipe is known for. The spodumene version is very similar, perhaps better. Notice my calculated cost: $15.47/kg vs. $8.12/kg.
This is a closeup of G3813B, a recipe with 11% spodumene. Although the glaze is very glossy, its surface is marred by tiny dimples, the remnant of broken and partially healed bubbles escapes. These bubbles were in the laydown and dried in place (the spodumene generates these in the slurry itself, making it frothy). This can be reduced by drop-and-hold firing techniques, but a better answer is to find a frit to source the Li2O.
This is what happens when some spodumenes are mixed with water. They generate foam and bubbles. This is disruptive in glazes and can be alleviated by washing and drying the powder before use. Or calcining at 500-600F.
GA6-C (left) and GA6-E (right) at cone 6 oxidation. The E version adds 4% spodumene onto the 4% rutile in the C (the base is 80% Alberta Slip and 20% frit 3134). The spodumene eliminate the overly whitish areas that can appear. This glaze requires the "Slow Cool (Reactive Glazes)" firing schedule. It looks the best on dark bodies.
L3362A speckle test cone 10R (G2240 spodumene) using ground iron stone concretions (50% 70-100 mesh, 35% 50-70 mesh, 15% 40-50 mesh) at 0.5%, 0.3%, 0.1% (left to right).
Out Bound Links
The hazards of this material in the ceramic industry and process
Undergoes an irreversible phase transition to yield beta-spodumene. This is accompanied by an expansion of ~30% and a decrease in specific gravity fro...
The toxicity of lithium in ceramics is a hotly debated subject, especially with regards to handling raw lithium carbonate, but also with reference to leaching from glazes.
While this is a trade-name of a specific type of ceramic available, the term is also used in a generic sense to refer to porcelain tableware that has an extremely low thermal expansion. While a trade secret of the Corning company, it is well known that oven-to-table ware is produced by controlling t...
In Bound Links
Tanco Spodumene Ore 200 mesh, Tanko Spod
Lith Carb, Li2CO3
Ausi Spodumene, Ausi Spod