The alkaline earth metals (abbreviation: RO) are our secondary fluxes and consist of Magnesia (MgO), Calcia (CaO), Strontia (SrO), Baria (BaO) and Zinc (ZnO).

Magnesium, Calcium, Srontium and Barium are found in the second column of the periodic table of elements.

Zinc is the anomaly.  It is found in the 12th column of the periodic table but behaves the same chemically, in a glaze, as the other alkaline earths.

Alkaline earths are sometimes referred to as the carbonates (RCO3 or RO-CO2) which generally mean fluxes that don’t contain Silica or Alumina.

Examples alkaline earths/carbonates are Magnesium carbonate (MgCO3), Calcium carbonate or Whiting (CaCO3), Calcium Magnesium carbonate or Dolomite (CaMg(CO3)2 ),  Strontium carbonate (SrCO3) and Barium carbonate (BaCO3).

Zinc comes in the form of Zinc oxide (ZnO).  It is not technically a carbonate but Zinc is in the alkaline earths group and may be grouped in with the carbonates with regards to its function in a glaze.

Magnesium silicate is called Talc (MgO-4SiO2-H2O) and is used as a source of Magnesium.

Calcium silicate is called Wollastonite (CaSiO3) and is used as a source of Calcium.

The alkaline earths play a large role in determining the colour response in a glaze.

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