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In ceramics, raw material chemistry is expressed a chemical analyses. This is in contrast to fired glaze chemistries which are expressed as oxide formulas.
How a Material Chemical Analysis is Done
Michael Banks and Stuart Altmann talk about chemical analyses methods and their advantages and disadvantages. Also information on testing labs you can use.
Glaze Chemistry Basics - Formula, Analysis, Mole%, Unity, LOI
Part of changing your viewpoint of glazes, from a collection of materials to a collection of oxides, is learning what a formula and analysis are, how conversion between the two is done and how unity and LOI impact this.