Iron glazes have their own page.
Willett Cobalt Green:
Gerstley borate 49g silica 32g EPK 19g Bentonite 2g chrome oxide 2g cobalt carbonate 1.5g COE: 5.2x10-6/K Stoneware (Tucker Smooth White) Source: Jim Willett Painted thickly on bisque, fired cone 6 electric. This glaze needs to be applied very thickly to keep its colour, but doesn't sag or move. Expansion is a bit low, so avoid high-expansion clays. Vase is 10 cm high. |
Boron Blue:
Fusion F12 frit 33g Fusion F2 frit 26g silica 24g EPK 17g copper carbonate 4g cobalt carbonate 1g white glue 0.3g COE: 5.5x10-6/K Stoneware (Tucker Smooth White), built from rolled slab. Add the white glue after sieving to keep the colorants in suspension. Painted on bisque medium thick. Fired cone 6 electric, held at maximum temperature (1210°C) for 30 min, kiln off. Drip catching bowl was needed, and grinding of base after. High gloss over all areas, no blisters, some of the colour phases but none of the crystallization that some have obtained. Has to be thick to get variations in colour. Probably best on work that has horizontal surfaces to contrast with vertical. Vase is 10 cm tall. |
Selsor Waxy White:
nepheline syenite 30g Gerstley borate 20g talc 18g zirconia 15g EPK 13g silica 10g calcite 9g COE: 5.6x10-6/K Stoneware (Tucker Smooth White), finger shaped. Source: Marica Selsor Painted thick on bisque. Fired cone 6 electric, held at maximum temperature (1220°C) for 10 min, kiln off. A soft white shading to light brown where thin. Even on a child's first finger pot, it gives a smooth surface with a lovely feel and excellent coverage. Mug is 6 cm tall. |
Turnidge Crystalline:
Fusion F75 frit 50g zinc oxide 22.5g silica 22.5g lithium carbonate 5g manganese dioxide 3g cobalt carbonate 1g COE: 7.7x10-6/K Stoneware (Tucker Smooth White) Painted thin on bisque, fired cone 6 electric. Crystalline glazes are known to be tricky. For me, crystals formed only at the edges of the blue with short soaks (30 min at 1000°C here); longer soaks resulted in the blue taking over completely. I couldn't persuade it to form the circular crystals that some have obtained. Its expansion is too high for it to be a functional glaze. Bowl is 8 cm diameter. |
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Zakin Clear
nepheline syenite 51g Gerstley borate 22g Wollastonite 14g EPK 8g zinc oxide 3g titanium dioxide 2g COE: 7.3x10-6/K Stoneware (Tucker Smooth White) | This is a fluid glaze that can be applied very thin and still seal evenly. Excellent for applying over non-toxic underglaze, but has too little silica to be functional with any colorant that could cause problems if it leached. It's expansion is high, but it withstands the usual freezer to boiling water test when dipped thinly on my stoneware. It will be safest on high-expansion clays. |
Marilee Lava:
Custer feldspar 50g calcite 24g EPK 13g silica 13g titanium dioxide 11g Mason 6600 stain 10g silicon carbide 600 mesh 0.3g COE: 6.7x10-6/K Stoneware (Tucker Smooth White), built from rolled slab. Dipped on bisque, fired cone 6 electric. This glaze gets its texture from calcite decomposition at 870°C (it's 40% CO2) followed by silicon carbide decomposition when alkalis in the glaze melt releasing more CO2 bubbles, and by being underfired therefore stiff at cone 6. Without the stain, it's white and can probably accept most colorants. More suitable for large scale pieces. Vase is 12 cm high. |
Cooling rates:
My kiln is a third-hand Olympic 1818WH electric manual single-brick-lined unit
43 cm diameter and 43 cm high inside. Switched on lowest power, it takes
1 hr to reach 500°C then on high power a further 2 hr to reach
cone 6, 1220°C. After a 10 min hold at 1220°C it takes
30 min when switched off to cool to 950°C, my usual hold temperature for
iron glazes.