Magnesium Oxide

Magnesium oxide (MgO) is a secondary flux analogous to calcium oxide.

• High MgO mattes a glaze
• MgO "thickens" the melt without increasing alumina
  • Increases surface tension
  • Alters crystal growth
    • Iron Red Glaze requires high MgO and low alumina to promote iron crystal growth
• MgO has lower expansion than CaO
  • Up to 0.1 molar reduces Crazing while preserving gloss

Materials

• Most commonly sourced from Talc and Dolomite
• Magnesium Carbonate is NOT a good source of magnesium in typical glazes
  • The physical properties of magnesium carbonate promotes crawling

Created 2024-07-20.

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