Barium oxide (BaO).
A vigorous flux. Baria lends brilliance and hardness to a glaze. Highly Toxic.
A basic oxide (Alkaline Earth).
The metal oxides that form salts when they come in contact with acids. See also, Acidic Oxides and Amphoteric Oxides .
Boric Oxide (B2O3).
A glass former which usually lowers thermal expansion and decreases viscosity .
An Acidic oxide (UK), Amphoteric Oxide (USA).