|Monthly Tech-Tip |
Alternate Names: Lithium Mica
It has a lower fusion point than most high temperature feldspars. The fluorine content can cause problems with glaze bubbles and surface pitting.
It is tricky to establish a formula weight and analysis for this material. Here are some of the factors:
-LOI varies, but we have assumed 5% water in this example.
-Lepidolite does not actually contain Li2O, it has to absorb oxygen from the atmosphere or other materials during firing since the Li is bonded to F.
-Fluorine is bonded to potassium so oxygen has to be absorbed to create K2O.
-For both Li and K only 1/2 of a molecule per input molecule of lepidolite will be yielded.
-In a complete oxidation firing all of the fluorine will volatilize and none will be in the final glass. However in real world conditions neither of these is likely to happen completely, and in a reduction firing neither may happen at all. In this case we are assuming it is all LOI.
Given the above assumptions, an input of LiF.KF.Al2O3.3SiO2 would yield:
Considering the F as LOI we would have the chemistry quoted here.
To properly handle a material like this in glaze chemistry fluorine conversion factors have to be employed.
Lepidolite at Mineral.galleries.com
Lepidolite at WebMineral.com
Lepidolite at Mindat.org
Lepidolite at Wikipedia
Although this material is sometimes referred to as a lithium feldspar, it is not a feldspar, but rat
|Oxides||Li2O - Lithium Oxide, Lithia|
Spodumene is a lithium sourcing feldspar, an alternative to lithium carbonate to supply Li2O to ceramic glazes. Contains up to about 8% Li2O.
Generic materials are those with no brand name. Normally they are theoretical, the chemistry portrays what a specimen would be if it had no contamination. Generic materials are helpful in educational situations where students need to study material theory (later they graduate to dealing with real world materials). They are also helpful where the chemistry of an actual material is not known. Often the accuracy of calculations is sufficient using generic materials.
The most common source of fluxes for high and medium temperature glazes and bodies.
|Density (Specific Gravity)||3.00|
|Frit Melting Range (C)||1150-1300C|
|By Tony Hansen|
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