Barium Oxide - BaO

Alkaline Earth Flux Unit 6 Topic 6
Oxide Qualities

High temperature flux - moderate expansion - alkaline colours - toxic.


  • A flux in the same category as CaO with varying degrees of activity.
  • Used in glazes fired over C.4 unless incorporated in a fritt with KNO.
  • Gives more brilliance than other alkaline earths but not as much as lead.
  • Has better fluxing action in small quantities interacting with other fluxes.
  • Larger amounts cause crystalisation which can give beautiful satin matts.


  • Barium carbonate BaCO3.
  • Barium sulphate (barytes) BaSO4 - can be used in a glaze but is impure. It is used in amounts of 1% or more in white clay bodies to remove the whitish scum resulting from calcium salts.

Colour Responses

  • With high levels gives alkaline blues with cobalt.
  • Apple greens with chrome.
  • A range of blues with nickel.
Barium carbonate is poisonous and should therefore be handled with caution. In a fired glaze containing BaO if there is an overload of this oxide, or the glaze is not durable, then there is a possibility that the oxide will leach out of the glaze when attacked by acids as can be the case in domestic ware ceramics.
Glazes recipes containing barium carbonate should not be used for liners inside domestic ware. The material may be used in other glazes where use with food is not involved however care must be taken in handling the raw material barium carbonate.

Check the health data on barium oxide. . . .
Check the health data on barium carbonate. . . .

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