(Sources: clays, hydrated minerals)
-Some suppliers will quote moisture or water in a material's analysis. Many materials are hydrated. An example is calcium sulfate. When it is heated past a certain point, the chemically bound water is expelled, converting the material into one of different chemistry.
-Chemical water in materials burns away during firing and so it has no impact on the fired chemistry. Since it is lost during firing, a weight of zero should be used if included in calculations.