Copyright © 1998 by Ian Currie
It is from this list that we will choose the Starting Point Glaze (No.31) With a little reading and experience we will be able to choose a flux set to suit a purpose. (We can actually do it at random with the possibility of very new and perhaps unreliable effects. ) The Rules of Thumb for Choosing a Flux Set summarises some characteristics for many of the more commonly used flux materials. A good text to consult for details of the properties of the fluxes listed below is Frank Hamer's "The Potter's Dictionary of Materials and Techniques".
The fluxes we choose will determine the set's temperature range. If we wish to get most of the set to melt at earthenware temperatures, it's advisable to have around 50% of a frit in Glaze No.31. There are many commercially available frits. It should be possible to obtain from the supplier a data sheet with an analysis and a brief description of the particular frit's main properties and uses.
The flux materials marked with * contain alumina and silica. We usually have at least one of these in our flux set. The flux materials marked with * are water soluble, and can therefore be absorbed into bisque, and can be difficult to control.
As well as being fluxes manganese carbonate and manganese dioxide are also colourants. They can be used up to 100% (in Glaze No.31), the higher range giving metallic glazes. The colourant iron oxide (not shown) is an active flux in reduction.
|Gerstley Borate||Similar to Colemanite with some Na|
|Magnesium carbonate (light)||3MgCO3.Mg(OH)2.3H2O|
|Nepheline syenite*||(K)NaO.Al2O3.4SiO2 (Approx)|
|Potassium carbonate (Pearl Ash)�||K2CO3|
|Rock powder A large range of rocks make excellent flux materials, e.g. basalt, granite.*|
|Sodium carbonate (Soda Ash)�||Na2CO3|
|Wood Ash* (May contain solubles�)||Variable, (often high in lime)|
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