|Monthly Tech-Tip |
Alternate Names: Fusion Frit F493
Description: High lithium, high alkali frit
This analysis was confirmed with Fusion Sept 2013. Excellent for replacing Spodumene in glazes (to eliminate its frothing and bubbling issues), this contains a higher percentage of lithia plus contributes other oxides that most glazes need. However it also has a very high thermal expansion.
This is an example of how much sense it makes to use a fritted form of a flux like lithia rather than the pure, and very troublesome, lithium carbonate. And it is fairly easy to do calculations (e.g. in your insight-live.com account) to substitute zinc in many existing boron fluxed recipes.
This should be more commonly available than it is. Volume users buy this by the pallet for their production, it's high cost amortizes down well considering the benefit it brings. A typical potter would be aghast at the price. Until he saw what this can do!
These materials have many issues. They can create problems in glaze slurries (like precipitates, higher drying shrinkage), cause issues with laydown density and produce fired surface defects (like pinholes, blisters, orange peeling, crystallization). Lithium and barium carbonates have toxicity issues and the carbon burns off during firing (with lithium, for example, 60% of its weight is lost). Yet the oxides that these materials supply to the glaze melt - ZnO, Li2O, BaO and SrO can be sourced from frits (removing most of the problems and imparting better glaze melting). Fusion Frit F-493 has 11% LI2O, F-403 has 35% BaO, F-581 has 39% SrO and FZ-16 has 15% ZnO. Of course, these frits source other oxides (but such are common in most glazes). Using glaze calculation you can often duplicate the chemistry of glazes while sourcing these oxides from frits. This being said, using the frits is about achieving a quality and avoid defects over concerns about their extra cost. Often the benefits lower the overall cost of production.
Frits are made by melting mixes of raw materials, quenching the melt in water, grinding the pebbles into a powder. Frits have chemistries raw materials cannot.
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.
Spodumene is a lithium sourcing feldspar, an alternative to lithium carbonate to supply Li2O to ceramic glazes. Contains up to about 8% Li2O.
A frit is the powdered form a man-made glass. Frits are premelted, then ground to a glass. They have tightly controlled chemistries, they are available for glazes of all types.
|Co-efficient of Linear Expansion||14.13|
|Frit Softening Point||1300F|
|By Tony Hansen|
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