- Strong alkaline flux
- Low toxicity
- Creates brightly colored glazes
- Exact melting point is 1652°F
- Begins melting at around 1580°F
- Best to begin to reduce high-sodium glazes at this point
- Powerful flux at all temperatures
- Often seen written as KNaO
- Similar to potassium oxide (K2O) in color response and expansion and contraction rate.
- Often insoluble sources include
- Some potassium oxide; ie: feldspar, which are the primary source of sodium in high-fire glazes
- Usually contain varying amounts of both sodium and potassium oxides
- Some potassium oxide; ie: feldspar, which are the primary source of sodium in high-fire glazes
- Most sources are soluble and can act as deflocculants in a glaze slurry or casting slip
- Glazes such as copper red or carbon trap shines, which have soluble sources of sodium oxide like soda ash, borax, or nepheline syenite, can easily become deflocculated.
- An interesting characteristic is that it’s volatile above 2012°F and will cause flashing on clay body as it leaves glaze
- Due to this effect it’s widely used in vapor glazing techniques like soda and salt firings
- Exhibits low viscosity and surface tension
- If used in high enough quantities it will cause glazes to run
- Has high expansion and contraction rate and will often cause crazing in glazes
- Creates soft glaze surfaces that are easily abraded by cutlery, acids, and bases (detergents).
- Insoluble source include sodium feldspars, Minspar, Kona F-4, NC-4, Bainbridge, Eureka, Godfrey, and cryolite.
- Also present in potash feldspars
- Including Custer, G-200, K-200, Plastic Vitrox, Cornwall Stone, volcanic ash, and rottenstone
- Soluble forms include soda ash, baking soda, salt, borax, unwashed woods, Gerstley Borate and its substitutes, and sodium silicate
- Nepheline syenite and Frits are slight soluble