- Alkaline earth flux
- Melts at 3493°F
- Active flux at high temps
- Forms strong eutectic with boron that can cause even matte glazes to run
- Gives strong, vivid colors, especially with copper and cobalt
- Produces excellent satin and matte surfaces from crystallization
- Worth noting because alumina (in the form of clay) is also used to create matte surfaces, but only produces dull colors.
- Can get both matte surfaces and vivid colors
- Sometimes used in small amounts to produce iron blue celadons
- Has high viscosity and medium surface tension
- Produces stiff glazes but will cause running in glazes that are fired too hot as fluxing power increases with temp
- Has a med expansion and contraction rate.
- Although isn’t volatile at ceramic temps keep in mind it’s extremely toxic, esp as a carb powder, when it becomes an airborne health hazard during mixing, and certainly if it leaches from fired glaze
- It was once used as a rat poison, so handle barium compounds with caution
- Barium glazes aren’t suitable for functional ware
- Under laboratory conditions (i.e., in pure water) it is almost insoluble in water, but in acidic solutions it can become soluble, making it easier to absorb into skin.
- Barium sulfate is insoluble and even has medical uses. It’s sometimes used to provide less toxic form of barium oxide in glazes and clay bodies (as in Wedgwood’s Jasperware), but does release sulfur fumes when fired.
- Soluble sources include barium carb (almost insoluble), and some Frits (slightly soluble); an insoluble source of it is barium sulfate.
