Sodium Oxide - Na2O

Alkali Flux Unit 6 Topic 1
Oxide Qualities

Very powerful flux - highest expansion - strong colour influence.


  • An active flux, increasing the fluidity of a melt.
  • Has highest coefficient of expansion therefore decreases the tensile strength and elasticity of the glaze and can increase the potential for crazing.
  • Usually combined with Na2O and expressed as KNO or KNa2O in unity formulae calculations.
  • Similar to potassium oxide.
  • Fuses at Cone 4.

Insoluble Sources

  • Feldspars (especially soda feldspars) for high temperature glazes.
  • Fritts - usually used in low temperature glazes.
  • Cryolite (not commonly used due to fluorine volatility).

Soluble Sources

Usually used in the creation of fritts.

  • Sodium Carbonate (soda ash), Sodium Bicarbonate - used in soda firings.
  • Sodium Chloride (salt) - used in salt firings.
  • Sodium Nitrate - soda nitre.
  • Borax.

Colour Responses

  • Alkaline - noted for unusual & exciting colours.
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